Android 系统（78）---《android framework常用api源码分析》之 app应用安装流程 《android framework常用api源码分析》之 app应用安装流程

《android framework常用api源码分析》之 app应用安装流程

《android framework常用api源码分析》android生态在中国已经发展非常庞大了，一方面是因为手机移动端的覆盖，另一方面是从事android开发的人也月来越多。那么用人单位对android要求也变了，对android不仅要熟练使用而且要懂得原理。而就程序员自身阅读源码有什么那些？这里我通过自己理解归纳了一下。

1. 提高程序执行效率，正确理解api可以高效使用，优化内存和执行效率。

2. 避免八阿哥强势逆袭，android开发同学都知道android找bug比较麻烦，尤其是一下jni底层调用错误信息不够明确地方更加难找。

3. 帮助自己写出优雅的代码，开发需要规范，而源码中有很多优秀的谷歌规范。

4. 优秀的设计模式，帮助自己提升程序造诣。

5. 黑科技，通过反射高一些api不能够达到的功能，例如插件化、热更新。

上面是简单个人理解，有更多补充欢迎留言。所以这里准备出一个系列的文章来分析android framework api， 这些文章也是来自整理于网络，所以要感谢那些具有分享精神的大神们。

文章目录：

1. apk 打包过程解析。
2. handler 消息机制。
3. AsyncTask 异步任务。
4. HandlerThread handler线程。
5. IntentService意图服务。
6. Zygote进程。
7. SystemServer进程。
8. Launcher 程序。
9. app 进程启动流程。
10. 系统app启动安装流程。
11. app应用安装流程。
12. Activity启动流程。
13. LruCache内存缓存

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android app安装时候基本原理都是通过adb底层来执行，但是用户操作的安装的时候一般都会有个安装界面并且有权限提示，点击安装的话就可以进行安装流程，那么今天就来分析安装流程中这些熟悉又陌生的系统安装app程序。上一篇文章中给大家分析了一下android系统启动之后调用PackageManagerService服务并解析系统特定目录，解析apk文件并安装的过程，这个安装过期实际上是没有图形界面的，底层调用的是我们平时比较熟悉的adb命令，那么我们平时安装apk文件的时候大部分是都过图形界面安装的，那么这种方式安装apk具体的流程是怎样的呢？ 
下面我们就来具体看一下apk的具体安装过程，相信大家都知道如果我们想在代码里执行apk的安装，那么一般都是这样：

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setDataAndType(Uri.parse("file://" + path),"application/vnd.android.package-archive");
context.startActivity(intent);

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这样，我们就会打开安装apk文件的程序并执行安装逻辑了，那么这段代码具体是打开那个activity呢？好吧，从这个问题开始，我们来解析apk的安装流程…

这里跟大姐简单介绍一下android的源码，平时我们使用的android.jar里面的java源码只是android系统源码的一部分，还有好多源码并没有打入到android.jar中，这里为大家推荐一个android源码的地址：https://github.com/android 
里面根据android系统的不同模块包含了许多android模块的源码。 

这里我们找到platform_packages_apps_packageinstaller库，这里面就是android系统安装程序的源码了。 

这里我们找到其androidManifest.xml，然后我们来看一下其具体的定义：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.android.packageinstaller" coreApp="true">

    <original-package android:name="com.android.packageinstaller" />

    ...

    <application android:label="@string/app_name"
            android:allowBackup="false"
            android:theme="@style/Theme.DialogWhenLarge"
            android:supportsRtl="true">

        <activity android:name=".PackageInstallerActivity"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:excludeFromRecents="true">
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="android.intent.action.INSTALL_PACKAGE" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:scheme="file" />
                <data android:mimeType="application/vnd.android.package-archive" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.intent.action.INSTALL_PACKAGE" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:scheme="file" />
                <data android:scheme="package" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.content.pm.action.CONFIRM_PERMISSIONS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

        <activity android:name=".InstallAppProgress"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:exported="false" />

        <activity android:name=".UninstallerActivity"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:excludeFromRecents="true"
                android:theme="@style/Theme.AlertDialogActivity">
            <intent-filter android:priority="1">
                <action android:name="android.intent.action.DELETE" />
                <action android:name="android.intent.action.UNINSTALL_PACKAGE" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:scheme="package" />
            </intent-filter>
        </activity>

        <activity android:name=".UninstallAppProgress"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:exported="false" />

        <activity android:name=".permission.ui.GrantPermissionsActivity"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:excludeFromRecents="true"
                android:theme="@style/GrantPermissions">
            <intent-filter>
                <action android:name="android.content.pm.action.REQUEST_PERMISSIONS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

        <activity android:name=".permission.ui.ManagePermissionsActivity"
                  android:configChanges="orientation|keyboardHidden|screenSize"
                  android:excludeFromRecents="true"
                  android:label="@string/app_permissions"
                  android:theme="@style/Settings"
                  android:permission="android.permission.GRANT_RUNTIME_PERMISSIONS">
            <intent-filter>
                <action android:name="android.intent.action.MANAGE_PERMISSIONS" />
                <action android:name="android.intent.action.MANAGE_APP_PERMISSIONS" />
                <action android:name="android.intent.action.MANAGE_PERMISSION_APPS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

        <activity android:name=".permission.ui.OverlayWarningDialog"
                android:excludeFromRecents="true"
                android:theme="@android:style/Theme.DeviceDefault.Light.Dialog.NoActionBar" />

        <provider android:name=".wear.WearPackageIconProvider"
                  android:authorities="com.google.android.packageinstaller.wear.provider"
                  android:grantUriPermissions="true"
                  android:exported="true" />

        <activity android:name=".permission.ui.wear.WarningConfirmationActivity"
                  android:permission="android.permission.GRANT_RUNTIME_PERMISSIONS"
                  android:theme="@style/Settings"/>
    </application>

</manifest>

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好吧，这里我们大概看一下Activity的定义，这里我们重点看一下PackageInstallerActivity的定义：

<activity android:name=".PackageInstallerActivity"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:excludeFromRecents="true">
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="android.intent.action.INSTALL_PACKAGE" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:scheme="file" />
                <data android:mimeType="application/vnd.android.package-archive" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.intent.action.INSTALL_PACKAGE" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:scheme="file" />
                <data android:scheme="package" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.content.pm.action.CONFIRM_PERMISSIONS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

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恩？这里不就是我们刚刚定义的启动安装Apk activity的intent filter？好吧，所以说一开始我们调用的startActivity其实启动的就是PackageInstallerActivity，那么下面我们就看一下PackageInstellerActivity的具体实现：

@Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        mPm = getPackageManager();
        mInstaller = mPm.getPackageInstaller();
        mUserManager = (UserManager) getSystemService(Context.USER_SERVICE);

        final Intent intent = getIntent();
        if (PackageInstaller.ACTION_CONFIRM_PERMISSIONS.equals(intent.getAction())) {
            final int sessionId = intent.getIntExtra(PackageInstaller.EXTRA_SESSION_ID, -1);
            final PackageInstaller.SessionInfo info = mInstaller.getSessionInfo(sessionId);
            if (info == null || !info.sealed || info.resolvedBaseCodePath == null) {
                Log.w(TAG, "Session " + mSessionId + " in funky state; ignoring");
                finish();
                return;
            }

            mSessionId = sessionId;
            mPackageURI = Uri.fromFile(new File(info.resolvedBaseCodePath));
            mOriginatingURI = null;
            mReferrerURI = null;
        } else {
            mSessionId = -1;
            mPackageURI = intent.getData();
            mOriginatingURI = intent.getParcelableExtra(Intent.EXTRA_ORIGINATING_URI);
            mReferrerURI = intent.getParcelableExtra(Intent.EXTRA_REFERRER);
        }

        final boolean unknownSourcesAllowedByAdmin = isUnknownSourcesAllowedByAdmin();
        final boolean unknownSourcesAllowedByUser = isUnknownSourcesEnabled();

        boolean requestFromUnknownSource = isInstallRequestFromUnknownSource(intent);
        mInstallFlowAnalytics = new InstallFlowAnalytics();
        mInstallFlowAnalytics.setContext(this);
        mInstallFlowAnalytics.setStartTimestampMillis(SystemClock.elapsedRealtime());
        mInstallFlowAnalytics.setInstallsFromUnknownSourcesPermitted(unknownSourcesAllowedByAdmin
                && unknownSourcesAllowedByUser);
        mInstallFlowAnalytics.setInstallRequestFromUnknownSource(requestFromUnknownSource);
        mInstallFlowAnalytics.setVerifyAppsEnabled(isVerifyAppsEnabled());
        mInstallFlowAnalytics.setAppVerifierInstalled(isAppVerifierInstalled());
        mInstallFlowAnalytics.setPackageUri(mPackageURI.toString());

        if (DeviceUtils.isWear(this)) {
            showDialogInner(DLG_NOT_SUPPORTED_ON_WEAR);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_NOT_ALLOWED_ON_WEAR);
            return;
        }

        final String scheme = mPackageURI.getScheme();
        if (scheme != null && !"file".equals(scheme) && !"package".equals(scheme)) {
            Log.w(TAG, "Unsupported scheme " + scheme);
            setPmResult(PackageManager.INSTALL_FAILED_INVALID_URI);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_FAILED_UNSUPPORTED_SCHEME);
            finish();
            return;
        }

        final PackageUtil.AppSnippet as;
        if ("package".equals(mPackageURI.getScheme())) {
            mInstallFlowAnalytics.setFileUri(false);
            try {
                mPkgInfo = mPm.getPackageInfo(mPackageURI.getSchemeSpecificPart(),
                        PackageManager.GET_PERMISSIONS | PackageManager.GET_UNINSTALLED_PACKAGES);
            } catch (NameNotFoundException e) {
            }
            if (mPkgInfo == null) {
                Log.w(TAG, "Requested package " + mPackageURI.getScheme()
                        + " not available. Discontinuing installation");
                showDialogInner(DLG_PACKAGE_ERROR);
                setPmResult(PackageManager.INSTALL_FAILED_INVALID_APK);
                mInstallFlowAnalytics.setPackageInfoObtained();
                mInstallFlowAnalytics.setFlowFinished(
                        InstallFlowAnalytics.RESULT_FAILED_PACKAGE_MISSING);
                return;
            }
            as = new PackageUtil.AppSnippet(mPm.getApplicationLabel(mPkgInfo.applicationInfo),
                    mPm.getApplicationIcon(mPkgInfo.applicationInfo));
        } else {
            mInstallFlowAnalytics.setFileUri(true);
            final File sourceFile = new File(mPackageURI.getPath());
            PackageParser.Package parsed = PackageUtil.getPackageInfo(sourceFile);

            // Check for parse errors
            if (parsed == null) {
                Log.w(TAG, "Parse error when parsing manifest. Discontinuing installation");
                showDialogInner(DLG_PACKAGE_ERROR);
                setPmResult(PackageManager.INSTALL_FAILED_INVALID_APK);
                mInstallFlowAnalytics.setPackageInfoObtained();
                mInstallFlowAnalytics.setFlowFinished(
                        InstallFlowAnalytics.RESULT_FAILED_TO_GET_PACKAGE_INFO);
                return;
            }
            mPkgInfo = PackageParser.generatePackageInfo(parsed, null,
                    PackageManager.GET_PERMISSIONS, 0, 0, null,
                    new PackageUserState());
            mPkgDigest = parsed.manifestDigest;
            as = PackageUtil.getAppSnippet(this, mPkgInfo.applicationInfo, sourceFile);
        }
        mInstallFlowAnalytics.setPackageInfoObtained();

        //set view
        setContentView(R.layout.install_start);
        mInstallConfirm = findViewById(R.id.install_confirm_panel);
        mInstallConfirm.setVisibility(View.INVISIBLE);
        PackageUtil.initSnippetForNewApp(this, as, R.id.app_snippet);

        mOriginatingUid = getOriginatingUid(intent);

        // Block the install attempt on the Unknown Sources setting if necessary.
        if (!requestFromUnknownSource) {
            initiateInstall();
            return;
        }

        // If the admin prohibits it, or we're running in a managed profile, just show error
        // and exit. Otherwise show an option to take the user to Settings to change the setting.
        final boolean isManagedProfile = mUserManager.isManagedProfile();
        if (!unknownSourcesAllowedByAdmin
                || (!unknownSourcesAllowedByUser && isManagedProfile)) {
            showDialogInner(DLG_ADMIN_RESTRICTS_UNKNOWN_SOURCES);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_BLOCKED_BY_UNKNOWN_SOURCES_SETTING);
        } else if (!unknownSourcesAllowedByUser) {
            // Ask user to enable setting first
            showDialogInner(DLG_UNKNOWN_SOURCES);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_BLOCKED_BY_UNKNOWN_SOURCES_SETTING);
        } else {
            initiateInstall();
        }
    }

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这里我们主要先看一下PackageInstallerActivity的onCreate方法：

@Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        mPm = getPackageManager();
        mInstaller = mPm.getPackageInstaller();
        mUserManager = (UserManager) getSystemService(Context.USER_SERVICE);

        final Intent intent = getIntent();
        if (PackageInstaller.ACTION_CONFIRM_PERMISSIONS.equals(intent.getAction())) {
            final int sessionId = intent.getIntExtra(PackageInstaller.EXTRA_SESSION_ID, -1);
            final PackageInstaller.SessionInfo info = mInstaller.getSessionInfo(sessionId);
            if (info == null || !info.sealed || info.resolvedBaseCodePath == null) {
                Log.w(TAG, "Session " + mSessionId + " in funky state; ignoring");
                finish();
                return;
            }

            mSessionId = sessionId;
            mPackageURI = Uri.fromFile(new File(info.resolvedBaseCodePath));
            mOriginatingURI = null;
            mReferrerURI = null;
        } else {
            mSessionId = -1;
            mPackageURI = intent.getData();
            mOriginatingURI = intent.getParcelableExtra(Intent.EXTRA_ORIGINATING_URI);
            mReferrerURI = intent.getParcelableExtra(Intent.EXTRA_REFERRER);
        }

        final boolean unknownSourcesAllowedByAdmin = isUnknownSourcesAllowedByAdmin();
        final boolean unknownSourcesAllowedByUser = isUnknownSourcesEnabled();

        boolean requestFromUnknownSource = isInstallRequestFromUnknownSource(intent);
        mInstallFlowAnalytics = new InstallFlowAnalytics();
        mInstallFlowAnalytics.setContext(this);
        mInstallFlowAnalytics.setStartTimestampMillis(SystemClock.elapsedRealtime());
        mInstallFlowAnalytics.setInstallsFromUnknownSourcesPermitted(unknownSourcesAllowedByAdmin
                && unknownSourcesAllowedByUser);
        mInstallFlowAnalytics.setInstallRequestFromUnknownSource(requestFromUnknownSource);
        mInstallFlowAnalytics.setVerifyAppsEnabled(isVerifyAppsEnabled());
        mInstallFlowAnalytics.setAppVerifierInstalled(isAppVerifierInstalled());
        mInstallFlowAnalytics.setPackageUri(mPackageURI.toString());

        if (DeviceUtils.isWear(this)) {
            showDialogInner(DLG_NOT_SUPPORTED_ON_WEAR);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_NOT_ALLOWED_ON_WEAR);
            return;
        }

        final String scheme = mPackageURI.getScheme();
        if (scheme != null && !"file".equals(scheme) && !"package".equals(scheme)) {
            Log.w(TAG, "Unsupported scheme " + scheme);
            setPmResult(PackageManager.INSTALL_FAILED_INVALID_URI);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_FAILED_UNSUPPORTED_SCHEME);
            finish();
            return;
        }

        final PackageUtil.AppSnippet as;
        if ("package".equals(mPackageURI.getScheme())) {
            mInstallFlowAnalytics.setFileUri(false);
            try {
                mPkgInfo = mPm.getPackageInfo(mPackageURI.getSchemeSpecificPart(),
                        PackageManager.GET_PERMISSIONS | PackageManager.GET_UNINSTALLED_PACKAGES);
            } catch (NameNotFoundException e) {
            }
            if (mPkgInfo == null) {
                Log.w(TAG, "Requested package " + mPackageURI.getScheme()
                        + " not available. Discontinuing installation");
                showDialogInner(DLG_PACKAGE_ERROR);
                setPmResult(PackageManager.INSTALL_FAILED_INVALID_APK);
                mInstallFlowAnalytics.setPackageInfoObtained();
                mInstallFlowAnalytics.setFlowFinished(
                        InstallFlowAnalytics.RESULT_FAILED_PACKAGE_MISSING);
                return;
            }
            as = new PackageUtil.AppSnippet(mPm.getApplicationLabel(mPkgInfo.applicationInfo),
                    mPm.getApplicationIcon(mPkgInfo.applicationInfo));
        } else {
            mInstallFlowAnalytics.setFileUri(true);
            final File sourceFile = new File(mPackageURI.getPath());
            PackageParser.Package parsed = PackageUtil.getPackageInfo(sourceFile);

            // Check for parse errors
            if (parsed == null) {
                Log.w(TAG, "Parse error when parsing manifest. Discontinuing installation");
                showDialogInner(DLG_PACKAGE_ERROR);
                setPmResult(PackageManager.INSTALL_FAILED_INVALID_APK);
                mInstallFlowAnalytics.setPackageInfoObtained();
                mInstallFlowAnalytics.setFlowFinished(
                        InstallFlowAnalytics.RESULT_FAILED_TO_GET_PACKAGE_INFO);
                return;
            }
            mPkgInfo = PackageParser.generatePackageInfo(parsed, null,
                    PackageManager.GET_PERMISSIONS, 0, 0, null,
                    new PackageUserState());
            mPkgDigest = parsed.manifestDigest;
            as = PackageUtil.getAppSnippet(this, mPkgInfo.applicationInfo, sourceFile);
        }
        mInstallFlowAnalytics.setPackageInfoObtained();

        //set view
        setContentView(R.layout.install_start);
        mInstallConfirm = findViewById(R.id.install_confirm_panel);
        mInstallConfirm.setVisibility(View.INVISIBLE);
        PackageUtil.initSnippetForNewApp(this, as, R.id.app_snippet);

        mOriginatingUid = getOriginatingUid(intent);

        // Block the install attempt on the Unknown Sources setting if necessary.
        if (!requestFromUnknownSource) {
            initiateInstall();
            return;
        }

        // If the admin prohibits it, or we're running in a managed profile, just show error
        // and exit. Otherwise show an option to take the user to Settings to change the setting.
        final boolean isManagedProfile = mUserManager.isManagedProfile();
        if (!unknownSourcesAllowedByAdmin
                || (!unknownSourcesAllowedByUser && isManagedProfile)) {
            showDialogInner(DLG_ADMIN_RESTRICTS_UNKNOWN_SOURCES);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_BLOCKED_BY_UNKNOWN_SOURCES_SETTING);
        } else if (!unknownSourcesAllowedByUser) {
            // Ask user to enable setting first
            showDialogInner(DLG_UNKNOWN_SOURCES);
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_BLOCKED_BY_UNKNOWN_SOURCES_SETTING);
        } else {
            initiateInstall();
        }
    }

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可以发现，在onCreate方法中，首先执行一些初始化操作，获取PackageManager和Installer、UserManager等对象，然后会根据当前Intent的信息最一些逻辑判断并弹出消息弹窗，我们可以看一下具体的消息弹窗类型：

private static final int DLG_BASE = 0;
    private static final int DLG_UNKNOWN_SOURCES = DLG_BASE + 1;
    private static final int DLG_PACKAGE_ERROR = DLG_BASE + 2;
    private static final int DLG_OUT_OF_SPACE = DLG_BASE + 3;
    private static final int DLG_INSTALL_ERROR = DLG_BASE + 4;
    private static final int DLG_ALLOW_SOURCE = DLG_BASE + 5;
    private static final int DLG_ADMIN_RESTRICTS_UNKNOWN_SOURCES = DLG_BASE + 6;
    private static final int DLG_NOT_SUPPORTED_ON_WEAR = DLG_BASE + 7;

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可以发现当分析Intent对象的时候，如果可以得到这样几种结果：不知道apk的来源，package信息错误，存储空间不够，安装时报，来源正确，允许未知来源的apk文件，在wear上不支持等，这样根据不同的消息类型会弹出不同的消息弹窗：

@Override
    public Dialog onCreateDialog(int id, Bundle bundle) {
        switch (id) {
        case DLG_UNKNOWN_SOURCES:
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.unknown_apps_dlg_title)
                    .setMessage(R.string.unknown_apps_dlg_text)
                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            Log.i(TAG, "Finishing off activity so that user can navigate to settings manually");
                            finish();
                        }})
                    .setPositiveButton(R.string.settings, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            Log.i(TAG, "Launching settings");
                            launchSecuritySettings();
                        }
                    })
                    .setOnCancelListener(this)
                    .create();
        case DLG_ADMIN_RESTRICTS_UNKNOWN_SOURCES:
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.unknown_apps_dlg_title)
                    .setMessage(R.string.unknown_apps_admin_dlg_text)
                    .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    .setOnCancelListener(this)
                    .create();
        case DLG_PACKAGE_ERROR :
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.Parse_error_dlg_title)
                    .setMessage(R.string.Parse_error_dlg_text)
                    .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    .setOnCancelListener(this)
                    .create();
        case DLG_OUT_OF_SPACE:
            // Guaranteed not to be null. will default to package name if not set by app
            CharSequence appTitle = mPm.getApplicationLabel(mPkgInfo.applicationInfo);
            String dlgText = getString(R.string.out_of_space_dlg_text,
                    appTitle.toString());
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.out_of_space_dlg_title)
                    .setMessage(dlgText)
                    .setPositiveButton(R.string.manage_applications, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            //launch manage applications
                            Intent intent = new Intent("android.intent.action.MANAGE_PACKAGE_STORAGE");
                            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                            startActivity(intent);
                            finish();
                        }
                    })
                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            Log.i(TAG, "Canceling installation");
                            finish();
                        }
                })
                  .setOnCancelListener(this)
                  .create();
        case DLG_INSTALL_ERROR :
            // Guaranteed not to be null. will default to package name if not set by app
            CharSequence appTitle1 = mPm.getApplicationLabel(mPkgInfo.applicationInfo);
            String dlgText1 = getString(R.string.install_failed_msg,
                    appTitle1.toString());
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.install_failed)
                    .setNeutralButton(R.string.ok, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    .setMessage(dlgText1)
                    .setOnCancelListener(this)
                    .create();
        case DLG_ALLOW_SOURCE:
            CharSequence appTitle2 = mPm.getApplicationLabel(mSourceInfo);
            String dlgText2 = getString(R.string.allow_source_dlg_text,
                    appTitle2.toString());
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.allow_source_dlg_title)
                    .setMessage(dlgText2)
                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            setResult(RESULT_CANCELED);
                            finish();
                        }})
                    .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            SharedPreferences prefs = getSharedPreferences(PREFS_ALLOWED_SOURCES,
                                    Context.MODE_PRIVATE);
                            prefs.edit().putBoolean(mSourceInfo.packageName, true).apply();
                            startInstallConfirm();
                        }
                    })
                    .setOnCancelListener(this)
                    .create();
        case DLG_NOT_SUPPORTED_ON_WEAR:
            return new AlertDialog.Builder(this)
                    .setTitle(R.string.wear_not_allowed_dlg_title)
                    .setMessage(R.string.wear_not_allowed_dlg_text)
                    .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            setResult(RESULT_OK);
                            finish();
                        }
                    })
                    .setOnCancelListener(this)
                    .create();
       }
       return null;
   }

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消息弹窗的主要作用，用于提示用户当前安装apk文件的特性。都知道android系统在android apk文件之前会解析器manifest文件，这个操作也是早onCreate方法中执行的：

PackageParser.Package parsed = PackageUtil.getPackageInfo(sourceFile);

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我们具体看一下getPackageInfo方法的实现：

public static PackageParser.Package getPackageInfo(File sourceFile) {
        final PackageParser parser = new PackageParser();
        try {
            PackageParser.Package pkg = parser.parseMonolithicPackage(sourceFile, 0);
            parser.collectManifestDigest(pkg);
            return pkg;
        } catch (PackageParserException e) {
            return null;
        }
    }

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好吧，到了这里是不是代码变得很熟悉了？parseMonolithicPackage就是我们上一节分析的android系统解析manifest文件的过程，而collectManifestDigest方法，我们这里简单的介绍一下，其主要是要争apk的签名是否正确。好吧通过这两部我们就把apk文件的manifest和签名信息都解析完成并保存在了Package中。 
接着往下走，在所有的解析完成之后我们会在onCreate方法中执行initiateInstall();方法，刚方法的主要作用是初始化安装。

private void initiateInstall() {
        String pkgName = mPkgInfo.packageName;
        // Check if there is already a package on the device with this name
        // but it has been renamed to something else.
        String[] oldName = mPm.canonicalToCurrentPackageNames(new String[] { pkgName });
        if (oldName != null && oldName.length > 0 && oldName[0] != null) {
            pkgName = oldName[0];
            mPkgInfo.packageName = pkgName;
            mPkgInfo.applicationInfo.packageName = pkgName;
        }
        // Check if package is already installed. display confirmation dialog if replacing pkg
        try {
            // This is a little convoluted because we want to get all uninstalled
            // apps, but this may include apps with just data, and if it is just
            // data we still want to count it as "installed".
            mAppInfo = mPm.getApplicationInfo(pkgName,
                    PackageManager.GET_UNINSTALLED_PACKAGES);
            if ((mAppInfo.flags&ApplicationInfo.FLAG_INSTALLED) == 0) {
                mAppInfo = null;
            }
        } catch (NameNotFoundException e) {
            mAppInfo = null;
        }

        mInstallFlowAnalytics.setReplace(mAppInfo != null);
        mInstallFlowAnalytics.setSystemApp(
                (mAppInfo != null) && ((mAppInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0));

        // If we have a session id, we're invoked to verify the permissions for the given
        // package. Otherwise, we start the install process.
        if (mSessionId != -1) {
            startInstallConfirm();
        } else {
            startInstall();
        }
    }

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好吧，这里面有调用了startInstallConfirm方法，然后我们看一下startInstallConfirm方法的实现:

private void startInstallConfirm() {
    ...
    //初始化安装确认界面
    ...
}

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好吧，这个方法的实现比较简单，主要的实现逻辑就是现实该activity的用户界面，平时我们安装某一个应用的时候会弹出一个安装确认页面，还有一个确认和取消按钮，有印象么？其实就是在这里执行的界面初始化操作。

好吧，一般情况下在apk安装确认页面，我们会点击确认按钮执行安装逻辑吧？那么这里我们找一下确认按钮的点击事件：

public void onClick(View v) {
        if (v == mOk) {
            if (mOkCanInstall || mScrollView == null) {
                mInstallFlowAnalytics.setInstallButtonClicked();
                if (mSessionId != -1) {
                    mInstaller.setPermissionsResult(mSessionId, true);

                    // We're only confirming permissions, so we don't really know how the
                    // story ends; assume success.
                    mInstallFlowAnalytics.setFlowFinishedWithPackageManagerResult(
                            PackageManager.INSTALL_SUCCEEDED);
                    finish();
                } else {
                    startInstall();
                }
            } else {
                mScrollView.pageScroll(View.FOCUS_DOWN);
            }
        } else if (v == mCancel) {
            // Cancel and finish
            setResult(RESULT_CANCELED);
            if (mSessionId != -1) {
                mInstaller.setPermissionsResult(mSessionId, false);
            }
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_CANCELLED_BY_USER);
            finish();
        }
    }

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很明显了，这里当我们点击确认按钮的时候会执行startInstall方法，也就是开始执行安装逻辑：

private void startInstall() {
        // Start subactivity to actually install the application
        Intent newIntent = new Intent();
        newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO,
                mPkgInfo.applicationInfo);
        newIntent.setData(mPackageURI);
        newIntent.setClass(this, InstallAppProgress.class);
        newIntent.putExtra(InstallAppProgress.EXTRA_MANIFEST_DIGEST, mPkgDigest);
        newIntent.putExtra(
                InstallAppProgress.EXTRA_INSTALL_FLOW_ANALYTICS, mInstallFlowAnalytics);
        String installerPackageName = getIntent().getStringExtra(
                Intent.EXTRA_INSTALLER_PACKAGE_NAME);
        if (mOriginatingURI != null) {
            newIntent.putExtra(Intent.EXTRA_ORIGINATING_URI, mOriginatingURI);
        }
        if (mReferrerURI != null) {
            newIntent.putExtra(Intent.EXTRA_REFERRER, mReferrerURI);
        }
        if (mOriginatingUid != VerificationParams.NO_UID) {
            newIntent.putExtra(Intent.EXTRA_ORIGINATING_UID, mOriginatingUid);
        }
        if (installerPackageName != null) {
            newIntent.putExtra(Intent.EXTRA_INSTALLER_PACKAGE_NAME,
                    installerPackageName);
        }
        if (getIntent().getBooleanExtra(Intent.EXTRA_RETURN_RESULT, false)) {
            newIntent.putExtra(Intent.EXTRA_RETURN_RESULT, true);
            newIntent.addFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
        }
        if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI);
        startActivity(newIntent);
        finish();
    }

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可以发现，点击确认按钮之后我们调用启用了一个新的Activity–>InstallAppProgress，这个Activity主要用于执行apk的安装逻辑了。

@Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        Intent intent = getIntent();
        mAppInfo = intent.getParcelableExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO);
        mInstallFlowAnalytics = intent.getParcelableExtra(EXTRA_INSTALL_FLOW_ANALYTICS);
        mInstallFlowAnalytics.setContext(this);
        mPackageURI = intent.getData();

        final String scheme = mPackageURI.getScheme();
        if (scheme != null && !"file".equals(scheme) && !"package".equals(scheme)) {
            mInstallFlowAnalytics.setFlowFinished(
                    InstallFlowAnalytics.RESULT_FAILED_UNSUPPORTED_SCHEME);
            throw new IllegalArgumentException("unexpected scheme " + scheme);
        }

        mInstallThread = new HandlerThread("InstallThread");
        mInstallThread.start();
        mInstallHandler = new Handler(mInstallThread.getLooper());

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BROADCAST_ACTION);
        registerReceiver(
                mBroadcastReceiver, intentFilter, BROADCAST_SENDER_PERMISSION, null /*scheduler*/);

        initView();
    }

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可以发现InstallAppProcess这个Activity的onCreate方法中主要初始化了一些成员变量，并调用initView方法，我们在iniTView方法中可以看到：

void initView() {
    ...
    mInstallHandler.post(new Runnable() {
                @Override
                public void run() {
                    doPackageStage(pm, params);
                }
            });
    ...
}

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经过一些view的初始化操作之后调用了doPackageStage方法，该方法主要是通过调用PackageInstaller执行apk文件的安装，这里就不在详细的介绍了，在apk文件安装完成之后PackageInstaller会发送一个安装完成的广播，刚刚我们在onCreate方法中注册了一个广播接收器，其可以用来接收apk安装完成的广播：

private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final int statusCode = intent.getIntExtra(
                    PackageInstaller.EXTRA_STATUS, PackageInstaller.STATUS_FAILURE);
            if (statusCode == PackageInstaller.STATUS_PENDING_USER_ACTION) {
                context.startActivity((Intent)intent.getParcelableExtra(Intent.EXTRA_INTENT));
            } else {
                onPackageInstalled(statusCode);
            }
        }
    };

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这样apk安装完成之后，这里的广播接收器会接收到广播并执行onPackageInstalled方法，执行后续的处理逻辑，那么我们来看一下onPackageInstalled方法的具体实现逻辑：

void onPackageInstalled(int statusCode) {
        Message msg = mHandler.obtainMessage(INSTALL_COMPLETE);
        msg.arg1 = statusCode;
        mHandler.sendMessage(msg);
    }

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好吧，这里是发送Handler异步消息，我们来看一下异步消息的处理逻辑：

private Handler mHandler = new Handler() {
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case INSTALL_COMPLETE:
                    mInstallFlowAnalytics.setFlowFinishedWithPackageManagerResult(msg.arg1);
                    if (getIntent().getBooleanExtra(Intent.EXTRA_RETURN_RESULT, false)) {
                        Intent result = new Intent();
                        result.putExtra(Intent.EXTRA_INSTALL_RESULT, msg.arg1);
                        setResult(msg.arg1 == PackageInstaller.STATUS_SUCCESS
                                ? Activity.RESULT_OK : Activity.RESULT_FIRST_USER,
                                        result);
                        finish();
                        return;
                    }
                    // Update the status text
                    mProgressBar.setVisibility(View.INVISIBLE);
                    // Show the ok button
                    int centerTextLabel;
                    int centerExplanationLabel = -1;
                    LevelListDrawable centerTextDrawable =
                            (LevelListDrawable) getDrawable(R.drawable.ic_result_status);
                    if (msg.arg1 == PackageInstaller.STATUS_SUCCESS) {
                        mLaunchButton.setVisibility(View.VISIBLE);
                        centerTextDrawable.setLevel(0);
                        centerTextLabel = R.string.install_done;
                        // Enable or disable launch button
                        mLaunchIntent = getPackageManager().getLaunchIntentForPackage(
                                mAppInfo.packageName);
                        boolean enabled = false;
                        if(mLaunchIntent != null) {
                            List<ResolveInfo> list = getPackageManager().
                                    queryIntentActivities(mLaunchIntent, 0);
                            if (list != null && list.size() > 0) {
                                enabled = true;
                            }
                        }
                        if (enabled) {
                            mLaunchButton.setOnClickListener(InstallAppProgress.this);
                        } else {
                            mLaunchButton.setEnabled(false);
                        }
                    } else if (msg.arg1 == PackageInstaller.STATUS_FAILURE_STORAGE){
                        showDialogInner(DLG_OUT_OF_SPACE);
                        return;
                    } else {
                        // Generic error handling for all other error codes.
                        centerTextDrawable.setLevel(1);
                        centerExplanationLabel = getExplanationFromErrorCode(msg.arg1);
                        centerTextLabel = R.string.install_failed;
                        mLaunchButton.setVisibility(View.INVISIBLE);
                    }
                    if (centerTextDrawable != null) {
                    centerTextDrawable.setBounds(0, 0,
                            centerTextDrawable.getIntrinsicWidth(),
                            centerTextDrawable.getIntrinsicHeight());
                        mStatusTextView.setCompoundDrawablesRelative(centerTextDrawable, null,
                                null, null);
                    }
                    mStatusTextView.setText(centerTextLabel);
                    if (centerExplanationLabel != -1) {
                        mExplanationTextView.setText(centerExplanationLabel);
                        mExplanationTextView.setVisibility(View.VISIBLE);
                    } else {
                        mExplanationTextView.setVisibility(View.GONE);
                    }
                    mDoneButton.setOnClickListener(InstallAppProgress.this);
                    mOkPanel.setVisibility(View.VISIBLE);
                    break;
                default:
                    break;
            }
        }
    };

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可以发现，当apk安装完成之后，我们会更新UI，显示完成和打开按钮，是不是和我们平时安装apk的逻辑对应上了？这时候我们可以看一下这两个按钮的点击事件。

public void onClick(View v) {
        if(v == mDoneButton) {
            if (mAppInfo.packageName != null) {
                Log.i(TAG, "Finished installing "+mAppInfo.packageName);
            }
            finish();
        } else if(v == mLaunchButton) {
            startActivity(mLaunchIntent);
            finish();
        }
    }

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好吧，比较简单，点击完成按钮，直接finish掉这个activity，点击打开，则直接调用startActivity启动安装的应用，然后直接finish自身。

总结：

• 代码中执行intent.setDataAndType(Uri.parse(“file://” + path),”application/vnd.android.package-archive”);可以调起PackageInstallerActivity；

• PackageInstallerActivity主要用于执行解析apk文件，解析manifest，解析签名等操作；

• InstallAppProcess主要用于执行安装apk逻辑，用于初始化安装界面，用于初始化用户UI。并调用PackageInstaller执行安装逻辑；

• InstallAppProcess内注册有广播，当安装完成之后接收广播，更新UI。显示apk安装完成界面；                                                                        转自