从Android AMS(四) Activity的窗口对象（Window）的创建过程分析知道，每一个Activity组件都有一个关联的Window对象，用来描述一个应用程序窗口。每一个应用程序窗口内部又包含有一个View对象，用来描述应用程序窗口的视图。应用程序窗口视图是真正用来实现UI内容和布局的，也就是说，每一个Activity组件的UI内容和布局都是通过与其所关联的一个Window对象的内部的一个View对象来实现的。在本文中，我们就详细分析应用程序窗口视图的创建过程。
在Android AMS(三) App启动过程之onResume中，我们提供过应用程序窗口内部所包含的视图对象的实际类型为DecorView。DecorView类继承了FrameLayout类，是作为容器（ViewGroup）来使用的
图盗用了老罗的O(∩_∩)O
从前面Android AMS(三) App启动过程之onResume一文还可以知道，每一个应用程序窗口的视图对象都有一个关联的ViewRootImpl对象，这些关联关系是由Window来维护的
简单来说，ViewRootImpl相当于是MVC模型中的Controller，它有以下职责：
1. 负责为应用程序窗口视图创建Surface。
2. 配合WindowManagerService来管理系统的应用程序窗口。
3. 负责管理、布局和渲染应用程序窗口视图的UI。
在 Android AMS(二) App启动过程之onCreate一文可以知道，Activity组件在启动的过程中，会调用ActivityThread类的成员函数handleLaunchActivity，用来创建以及首次激活Activity组件，因此，接下来我们就从这个函数开始，具体分析应用程序窗口的视图对象及其所关联的ViewRootImpl对象的创建过程
1. ActivityThread.java-->handleLaunchActivity()
public final class ActivityThread {
......
private final void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {
......
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
......
handleResumeActivity(r.token, false, r.isForward);
......
}
......
}
......
}
函数首先调用ActivityThread类的成员函数performLaunchActivity来创建要启动的Activity组件。在创建Activity组件的过程中，还会为该Activity组件创建窗口对象和视图对象。Activity组件创建完成之后，就可以将它激活起来了，这是通过调用ActivityThread类的成员函数handleResumeActivity来执行的。
接下来，我们首先分析ActivityThread类的成员函数performLaunchActivity的实现，以便可以了解应用程序窗口视图对象的创建过程，接着再回过头来继续分析ActivityThread类的成员函数handleResumeActivity的实现，以便可以了解与应用程序窗口视图对象所关联的ViewRootImpl对象的创建过程。
2. ActivityThread.java-->performLaunchActivity()
在 Android AMS(二) App启动过程之onCreate一文可以知道,performLaunchActivity()最终会调用到Activity.onCreate(),而
我们在实现一个Activity组件的时候，也就是在实现一个Activity子类的时候，一般都会重写成员函数onCreate，以便可以执行一些自定义的初始化工作，其中就包含初始化UI的工作，例如：
public class Hello extends Activity {
......
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
......
}
......
}
其中，调用从父类Activity继承下来的成员函数setContentView就是用来创建应用程序窗口视图对象的。接下来，我们就继续分析Activity类的成员函数setContentView的实现。
3. Activity.java-->setContentView()
public class Activity extends ContextThemeWrapper
implements LayoutInflater.Factory2,
Window.Callback, KeyEvent.Callback,
OnCreateContextMenuListener, ComponentCallbacks2,
Window.OnWindowDismissedCallback, WindowControllerCallback,
AutofillManager.AutofillClient{
......
private Window mWindow;
......
public Window getWindow() {
return mWindow;
}
......
public void setContentView(int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
......
}
Activity类的成员函数setContentView首先调用另外一个成员函数getWindow来获得成员变量mWindow所描述的一个窗口对象，接着再调用这个窗口对象的成员函数setContentView来执行创建应用程序窗口视图对象的工作。
从前面Android AMS(四) Activity的窗口对象（Window）的创建过程分析一文可以知道，Activity类的成员变量mWindow指向的是一个PhoneWindow对象，因此，接下来我们就继续分析PhoneWindow类的成员函数setContentView的实现。
@Override
public void setContentView(int layoutResID) {
// Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. Do not check the feature
// before this happens.
if (mContentParent == null) {
installDecor();
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
mLayoutInflater.inflate(layoutResID, mContentParent);
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
mContentParentExplicitlySet = true;
}PhoneWindow类的成员变量mContentParent用来描述一个类型为DecorView的视图对象，或者这个类型为DecorView的视图对象的一个子视图对象，用作UI容器。当它的值等于null的时候，就说明正在处理的应用程序窗口的视图对象还没有创建。在这种情况下，就会调用成员函数installDecor来创建应用程序窗口视图对象。否则的话，就说明是要重新设置应用程序窗口的视图。在重新设置之前，首先调用成员变量mContentParent所描述的一个ViewGroup对象来移除原来的UI内空。
由于我们是在Activity组件启动的过程中创建应用程序窗口视图的，因此，我们就假设此时PhoneWindow类的成员变量mContentParent的值等于null。接下来，函数就会调用成员函数installDecor来创建应用程序窗口视图对象，接着再通过调用PhoneWindow类的成员变量mLayoutInflater所描述的一个LayoutInflater对象的成员函数inflate来将参数layoutResID所描述的一个UI布局设置到前面所创建的应用程序窗口视图中去，最后还会调用一个Callback接口的成员函数onContentChanged来通知对应的Activity组件，它的视图内容发生改变了。从前面Android AMS(四) Activity的窗口对象（Window）的创建过程分析一文可以知道，Activity组件自己实现了这个Callback接口，并且将这个Callback接口设置到了与它所关联的应用程序窗口对象的内部去，因此，前面实际调用的是Activity类的成员函数onContentChanged来发出一个视图内容变化通知。
接下来，我们就继续分析PhoneWindow类的成员函数installDecor的实现，以便可以继续了解应用程序窗口视图对象的创建过程
4.PhoneWindow.java-->installDecor()
private void installDecor() {
mForceDecorInstall = false;
if (mDecor == null) {
mDecor = generateDecor(-1);
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
} else {
mDecor.setWindow(this);
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);
// Set up decor part of UI to ignore fitsSystemWindows if appropriate.
mDecor.makeOptionalFitsSystemWindows();
final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(
R.id.decor_content_parent);
if (decorContentParent != null) {
mDecorContentParent = decorContentParent;
mDecorContentParent.setWindowCallback(getCallback());
if (mDecorContentParent.getTitle() == null) {
mDecorContentParent.setWindowTitle(mTitle);
}
final int localFeatures = getLocalFeatures();
for (int i = 0; i < FEATURE_MAX; i++) {
if ((localFeatures & (1 << i)) != 0) {
mDecorContentParent.initFeature(i);
}
}
mDecorContentParent.setUiOptions(mUiOptions);
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) != 0 ||
(mIconRes != 0 && !mDecorContentParent.hasIcon())) {
mDecorContentParent.setIcon(mIconRes);
} else if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) == 0 &&
mIconRes == 0 && !mDecorContentParent.hasIcon()) {
mDecorContentParent.setIcon(
getContext().getPackageManager().getDefaultActivityIcon());
mResourcesSetFlags |= FLAG_RESOURCE_SET_ICON_FALLBACK;
}
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_LOGO) != 0 ||
(mLogoRes != 0 && !mDecorContentParent.hasLogo())) {
mDecorContentParent.setLogo(mLogoRes);
}
// Invalidate if the panel menu hasn't been created before this.
// Panel menu invalidation is deferred avoiding application onCreateOptionsMenu
// being called in the middle of onCreate or similar.
// A pending invalidation will typically be resolved before the posted message
// would run normally in order to satisfy instance state restoration.
PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false);
if (!isDestroyed() && (st == null || st.menu == null) && !mIsStartingWindow) {
invalidatePanelMenu(FEATURE_ACTION_BAR);
}
} else {
mTitleView = findViewById(R.id.title);
if (mTitleView != null) {
//判断标题栏是否显示
if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {
final View titleContainer = findViewById(R.id.title_container);
if (titleContainer != null) {
titleContainer.setVisibility(View.GONE);
} else {
mTitleView.setVisibility(View.GONE);
}
mContentParent.setForeground(null);
} else {
mTitleView.setText(mTitle);
}
}
}
if (mDecor.getBackground() == null && mBackgroundFallbackResource != 0) {
mDecor.setBackgroundFallback(mBackgroundFallbackResource);
}
// Only inflate or create a new TransitionManager if the caller hasn't
// already set a custom one.
if (hasFeature(FEATURE_ACTIVITY_TRANSITIONS)) {
if (mTransitionManager == null) {
final int transitionRes = getWindowStyle().getResourceId(
R.styleable.Window_windowContentTransitionManager,
0);
if (transitionRes != 0) {
final TransitionInflater inflater = TransitionInflater.from(getContext());
mTransitionManager = inflater.inflateTransitionManager(transitionRes,
mContentParent);
} else {
mTransitionManager = new TransitionManager();
}
}
mEnterTransition = getTransition(mEnterTransition, null,
R.styleable.Window_windowEnterTransition);
mReturnTransition = getTransition(mReturnTransition, USE_DEFAULT_TRANSITION,
R.styleable.Window_windowReturnTransition);
mExitTransition = getTransition(mExitTransition, null,
R.styleable.Window_windowExitTransition);
mReenterTransition = getTransition(mReenterTransition, USE_DEFAULT_TRANSITION,
R.styleable.Window_windowReenterTransition);
mSharedElementEnterTransition = getTransition(mSharedElementEnterTransition, null,
R.styleable.Window_windowSharedElementEnterTransition);
mSharedElementReturnTransition = getTransition(mSharedElementReturnTransition,
USE_DEFAULT_TRANSITION,
R.styleable.Window_windowSharedElementReturnTransition);
mSharedElementExitTransition = getTransition(mSharedElementExitTransition, null,
R.styleable.Window_windowSharedElementExitTransition);
mSharedElementReenterTransition = getTransition(mSharedElementReenterTransition,
USE_DEFAULT_TRANSITION,
R.styleable.Window_windowSharedElementReenterTransition);
if (mAllowEnterTransitionOverlap == null) {
mAllowEnterTransitionOverlap = getWindowStyle().getBoolean(
R.styleable.Window_windowAllowEnterTransitionOverlap, true);
}
if (mAllowReturnTransitionOverlap == null) {
mAllowReturnTransitionOverlap = getWindowStyle().getBoolean(
R.styleable.Window_windowAllowReturnTransitionOverlap, true);
}
if (mBackgroundFadeDurationMillis < 0) {
mBackgroundFadeDurationMillis = getWindowStyle().getInteger(
R.styleable.Window_windowTransitionBackgroundFadeDuration,
DEFAULT_BACKGROUND_FADE_DURATION_MS);
}
if (mSharedElementsUseOverlay == null) {
mSharedElementsUseOverlay = getWindowStyle().getBoolean(
R.styleable.Window_windowSharedElementsUseOverlay, true);
}
}
}
}由于我们是在Activity组件启动的过程中创建应用程序窗口视图的，因此，我们同时假设此时PhoneWindow类的成员变量mDecor的值等于null。这时候PhoneWindow类的成员函数installDecor就会调用另外一个成员函数generateDecor来创建一个DecorView对象，并且保存在PhoneWindow类的成员变量mDecor中。
PhoneWindow类的成员函数installDecor接着再调用另外一个成员函数generateLayout来根据当前应用程序窗口的Feature来加载对应的窗口布局文件。这些布局文件保存在frameworks/base/core/res/res/layout目录下，它们必须包含有一个id值为“content”的布局控件。这个布局控件必须要从ViewGroup类继承下来，用来作为窗口的UI容器。PhoneWindow类的成员函数generateLayout执行完成之后，就会这个id值为“content”的ViewGroup控件来给PhoneWindow类的成员函数installDecor，后者再将其保存在成员变量mContentParent中。
PhoneWindow类的成员函数installDecor还会检查前面加载的窗口布局文件是否包含有一个id值为“title”的TextView控件。如果包含有的话，就会将它保存在PhoneWindow类的成员变量mTitleView中，用来描述当前应用程序窗口的标题栏。但是，如果当前应用程序窗口是没有标题栏的，即它的Feature位FEATURE_NO_TITLE的值等于1，那么PhoneWindow类的成员函数installDecor就需要将前面得到的标题栏隐藏起来。注意，PhoneWindow类的成员变量mTitleView所描述的标题栏有可能是包含在一个id值为“title_container”的容器里面的，在这种情况下，就需要隐藏该标题栏容器。另一方面，如果当前应用程序窗口是设置有标题栏的，那么PhoneWindow类的成员函数installDecor就会设置它的标题栏文字。应用程序窗口的标题栏文字保存在PhoneWindow类的成员变量mTitle中，我们可以调用PhoneWindow类的成员函数setTitle来设置。
这一步执行完成之后，应用程序窗口视图就创建完成了。接下来就会调用ActivityThread类的另外一个成员函数handleResumeActivity来激活正在启动的Activity组件。由于在是第一次激活该Activity组件，因此，在激活之前，还会为该Activity组件创建一个ViewRootImpl对象，并且与前面所创建的应用程序窗口视图关联起来，以便后面可以通过该ViewRootImpl对象来控制应用程序窗口视图的UI展现。
5. ActivityThread.java-->handleResumeActivity()
public final class ActivityThread {
......
final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward) {
......
ActivityClientRecord r = performResumeActivity(token, clearHide);
if (r != null) {
final Activity a = r.activity;
......
// If the window hasn't yet been added to the window manager,
// and this guy didn't finish itself or start another activity,
// then go ahead and add the window.
boolean willBeVisible = !a.mStartedActivity;
if (!willBeVisible) {
try {
willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(
a.getActivityToken());
} catch (RemoteException e) {
}
}
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
......
if (a.mVisibleFromClient) {
a.mWindowAdded = true;
wm.addView(decor, l);
}
}
......
}
......
}
......
}
ActivityThread类的成员函数handleResumeActivity首先调用另外一个成员函数performResumeActivity来通知Activity组件，它要被激活了，即会导致Activity组件的成员函数onResume被调用。ActivityThread类的成员函数performResumeActivity的返回值是一个ActivityClientRecord对象r，这个ActivityClientRecord对象的成员变量activity描述的就是正在激活的Activity组件a
在Android AMS(四) Activity的窗口对象（Window）的创建过程分析一文可以知道，Activity类的成员变量mWindow指向的是一个类型为PhoneWindow的窗口对象，因此，Activity类的成员函数getWindow返回给调用者的是一个PhoneWindow对象。接下来就会继续调用前面所获得的一个PhoneWindow对象的成员函数getDecorView来获得当前正在激活的Activity组件所关联的一个应用程序窗口视图对象。继续调用当前正在激活的Activity组件的成员函数getWindowManager来获得一个窗口管理器WindowManagerImpl。最后调用WindowManagerImpl的addView来为当前正在激活的Activity组件的应用程序窗口视图对象关联一个ViewRootImpl对象。
WindowManagerImpl.java-->addView()
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}WindowManagerImpl将具体的实现方式放在了WindowManagerGlobal这个类里，这就是典型的桥接模式
WindowManagerGlobal.java-->addView()
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
if (display == null) {
throw new IllegalArgumentException("display must not be null");
}
if (!(params instanceof WindowManager.LayoutParams)) {
throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
}
final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
if (parentWindow != null) {
parentWindow.adjustLayoutParamsForSubWindow(wparams);
} else {
// If there's no parent, then hardware acceleration for this view is
// set from the application's hardware acceleration setting.
final Context context = view.getContext();
if (context != null
&& (context.getApplicationInfo().flags
& ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
}
}
ViewRootImpl root;
View panelParentView = null;
synchronized (mLock) {
// Start watching for system property changes.
if (mSystemPropertyUpdater == null) {
mSystemPropertyUpdater = new Runnable() {
@Override public void run() {
synchronized (mLock) {
for (int i = mRoots.size() - 1; i >= 0; --i) {
mRoots.get(i).loadSystemProperties();
}
}
}
};
SystemProperties.addChangeCallback(mSystemPropertyUpdater);
}
int index = findViewLocked(view, false);
if (index >= 0) {
if (mDyingViews.contains(view)) {
// Don't wait for MSG_DIE to make it's way through root's queue.
mRoots.get(index).doDie();
} else {
throw new IllegalStateException("View " + view
+ " has already been added to the window manager.");
}
// The previous removeView() had not completed executing. Now it has.
}
// If this is a panel window, then find the window it is being
// attached to for future reference.
if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
final int count = mViews.size();
for (int i = 0; i < count; i++) {
if (mRoots.get(i).mWindow.asBinder() == wparams.token) {
panelParentView = mViews.get(i);
}
}
}
root = new SprdViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
// do this last because it fires off messages to start doing things
try {
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
}
}WindowManagerGlobal类有三个成员变量mViews、mRoots和mParams，它们分别是类型为View、ViewRoot和WindowManager.LayoutParams的数组。这三个数组的大小是始终保持相等的。
private final ArrayList<View> mViews = new ArrayList<View>();
private final MyArrayList<ViewRootImpl> mRoots = new MyArrayList<ViewRootImpl>();
private final ArrayList<WindowManager.LayoutParams> mParams =
new ArrayList<WindowManager.LayoutParams>();ViewRootImpl.java-->setView()
public class ViewRootImpl extends AbsViewRootImpl implements ViewParent,
View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks {
......
final WindowManager.LayoutParams mWindowAttributes = new WindowManager.LayoutParams();
......
View mView;
......
final View.AttachInfo mAttachInfo;
......
boolean mAdded;
......
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
mAttachInfo.mDisplayState = mDisplay.getState();
mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
mViewLayoutDirectionInitial = mView.getRawLayoutDirection();
mFallbackEventHandler.setView(view);
mWindowAttributes.copyFrom(attrs);
if (mWindowAttributes.packageName == null) {
mWindowAttributes.packageName = mBasePackageName;
}
attrs = mWindowAttributes;
setTag();
if (DEBUG_KEEP_SCREEN_ON && (mClientWindowLayoutFlags
& WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) != 0
&& (attrs.flags&WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) == 0) {
Slog.d(mTag, "setView: FLAG_KEEP_SCREEN_ON changed from true to false!");
}
// Keep track of the actual window flags supplied by the client.
mClientWindowLayoutFlags = attrs.flags;
setAccessibilityFocus(null, null);
if (view instanceof RootViewSurfaceTaker) {
mSurfaceHolderCallback =
((RootViewSurfaceTaker)view).willYouTakeTheSurface();
if (mSurfaceHolderCallback != null) {
mSurfaceHolder = new TakenSurfaceHolder();
mSurfaceHolder.setFormat(PixelFormat.UNKNOWN);
mSurfaceHolder.addCallback(mSurfaceHolderCallback);
}
}
// Compute surface insets required to draw at specified Z value.
// TODO: Use real shadow insets for a constant max Z.
if (!attrs.hasManualSurfaceInsets) {
attrs.setSurfaceInsets(view, false /*manual*/, true /*preservePrevious*/);
}
CompatibilityInfo compatibilityInfo =
mDisplay.getDisplayAdjustments().getCompatibilityInfo();
mTranslator = compatibilityInfo.getTranslator();
// If the application owns the surface, don't enable hardware acceleration
if (mSurfaceHolder == null) {
enableHardwareAcceleration(attrs);
}
boolean restore = false;
if (mTranslator != null) {
mSurface.setCompatibilityTranslator(mTranslator);
restore = true;
attrs.backup();
mTranslator.translateWindowLayout(attrs);
}
if (DEBUG_LAYOUT) Log.d(mTag, "WindowLayout in setView:" + attrs);
if (!compatibilityInfo.supportsScreen()) {
attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
mLastInCompatMode = true;
}
mSoftInputMode = attrs.softInputMode;
mWindowAttributesChanged = true;
mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;
mAttachInfo.mRootView = view;
mAttachInfo.mScalingRequired = mTranslator != null;
mAttachInfo.mApplicationScale =
mTranslator == null ? 1.0f : mTranslator.applicationScale;
if (panelParentView != null) {
mAttachInfo.mPanelParentWindowToken
= panelParentView.getApplicationWindowToken();
}
mAdded = true;
int res; /* = WindowManagerImpl.ADD_OKAY; */
// Schedule the first layout -before- adding to the window
// manager, to make sure we do the relayout before receiving
// any other events from the system.
requestLayout();
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
mInputChannel = new InputChannel();
}
mForceDecorViewVisibility = (mWindowAttributes.privateFlags
& PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY) != 0;
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
} catch (RemoteException e) {
mAdded = false;
mView = null;
mAttachInfo.mRootView = null;
mInputChannel = null;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
throw new RuntimeException("Adding window failed", e);
} finally {
if (restore) {
attrs.restore();
}
}
if (mTranslator != null) {
mTranslator.translateRectInScreenToAppWindow(mAttachInfo.mContentInsets);
}
mPendingOverscanInsets.set(0, 0, 0, 0);
mPendingContentInsets.set(mAttachInfo.mContentInsets);
mPendingStableInsets.set(mAttachInfo.mStableInsets);
mPendingVisibleInsets.set(0, 0, 0, 0);
mAttachInfo.mAlwaysConsumeNavBar =
(res & WindowManagerGlobal.ADD_FLAG_ALWAYS_CONSUME_NAV_BAR) != 0;
mPendingAlwaysConsumeNavBar = mAttachInfo.mAlwaysConsumeNavBar;
if (DEBUG_LAYOUT) Log.v(mTag, "Added window " + mWindow);
if (res < WindowManagerGlobal.ADD_OKAY) {
mAttachInfo.mRootView = null;
mAdded = false;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
switch (res) {
case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not valid; is your activity running?");
case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not for an application");
case WindowManagerGlobal.ADD_APP_EXITING:
throw new WindowManager.BadTokenException(
"Unable to add window -- app for token " + attrs.token
+ " is exiting");
case WindowManagerGlobal.ADD_DUPLICATE_ADD:
throw new WindowManager.BadTokenException(
"Unable to add window -- window " + mWindow
+ " has already been added");
case WindowManagerGlobal.ADD_STARTING_NOT_NEEDED:
// Silently ignore -- we would have just removed it
// right away, anyway.
return;
case WindowManagerGlobal.ADD_MULTIPLE_SINGLETON:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- another window of type "
+ mWindowAttributes.type + " already exists");
case WindowManagerGlobal.ADD_PERMISSION_DENIED:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- permission denied for window type "
+ mWindowAttributes.type);
case WindowManagerGlobal.ADD_INVALID_DISPLAY:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified display can not be found");
case WindowManagerGlobal.ADD_INVALID_TYPE:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified window type "
+ mWindowAttributes.type + " is not valid");
}
throw new RuntimeException(
"Unable to add window -- unknown error code " + res);
}
if (view instanceof RootViewSurfaceTaker) {
mInputQueueCallback =
((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();
}
if (mInputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
}
view.assignParent(this);
mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
if (mAccessibilityManager.isEnabled()) {
mAccessibilityInteractionConnectionManager.ensureConnection();
}
if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
// Set up the input pipeline.
CharSequence counterSuffix = attrs.getTitle();
mSyntheticInputStage = new SyntheticInputStage();
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
mFirstInputStage = nativePreImeStage;
mFirstPostImeInputStage = earlyPostImeStage;
mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
}
}
}
}参数view所描述的一个View对象会分别被保存在ViewRootImpl类的成员变量mView以及成员变量mAttachInfo所描述的一个AttachInfo的成员变量mRootView中，而参数attrs所描述的一个WindowManager.LayoutParams对象的内容会被拷贝到ViewRoot类的成员变量mWindowAttributes中去。
当参数panelParentView的值不等于null的时候，就表示参数view描述的是一个子应用程序窗口视图对象。在这种情况下，参数panelParentView描述的就是一个父应用程序窗口视图对象。这时候我们就需要获得用来描述这个父应用程序窗口视图对象的一个类型为W的Binder本地对象的IBinder接口，以便可以保存在ViewRoot类的成员变量mAttachInfo所描述的一个AttachInfo的成员变量mPanelParentWindowToken中去。这样以后就可以知道ViewRoot类的成员变量mView所描述的一个子应用程序窗口视图所属的父应用程序窗口视图是什么了。注意，通过调用参数panelParentView的所描述的一个View对象的成员函数getApplicationWindowToken即可以获得一个对应的W对象的IBinder接口。
上述操作执行完成之后，ViewRootImpl类的成员函数setView就可以将成员变量mAdded的值设置为true了，表示当前正在处理的一个ViewRootImpl对象已经关联好一个View对象了。接下来，ViewRootImpl类的成员函数setView还需要执行两个操作：
1. 调用ViewRootImpl类的另外一个成员函数requestLayout来请求对应用程序窗口视图的UI作第一次布局。
2. 调用ViewRootImpl类的静态成员变量sWindowSession所描述的一个类型为Session的Binder代理对象的成员函数addToDisplay来请求WindowManagerService增加一个WindowState对象，以便可以用来描述当前正在处理的一个ViewRootImpl所关联的一个应用程序窗口
3. new WindowInputEventReceiver 负责监听IO事件