先看一下app widget的添加代码，此处直接引用http://www.cnblogs.com/wanqieddy/archive/2012/05/05/2484533.html的代码
package com.qin.addappwidget;
import android.app.Activity;
import android.appwidget.AppWidgetHost;
import android.appwidget.AppWidgetHostView;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProviderInfo;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity
{
private static String TAG = "AddAppWidget" ;
private Button btAddShortCut;
private LinearLayout linearLayout ; // 装载Appwidget的父视图
private static final int MY_REQUEST_APPWIDGET = 1;
private static final int MY_CREATE_APPWIDGET = 2;
private static final int HOST_ID = 1024 ;
private AppWidgetHost mAppWidgetHost = null ;
AppWidgetManager appWidgetManager = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btAddShortCut = (Button) findViewById(R.id.bt_addShortcut);
linearLayout = (LinearLayout)findViewById(R.id.linearLayout) ;
//其参数hostid大意是指定该AppWidgetHost 即本Activity的标记Id， 直接设置为一个整数值吧 。
mAppWidgetHost = new AppWidgetHost(MainActivity.this, HOST_ID) ;
//为了保证AppWidget的及时更新 ， 必须在Activity的onCreate/onStar方法调用该方法
// 当然可以在onStop方法中，调用mAppWidgetHost.stopListenering() 停止AppWidget更新
mAppWidgetHost.startListening() ;
//获得AppWidgetManager对象
appWidgetManager = AppWidgetManager.getInstance(MainActivity.this) ;
btAddShortCut.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
//显示所有能创建AppWidget的列表 发送此 ACTION_APPWIDGET_PICK 的Action
Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK) ;
//向系统申请一个新的appWidgetId ，该appWidgetId与我们发送Action为ACTION_APPWIDGET_PICK
// 后所选择的AppWidget绑定 。 因此，我们可以通过这个appWidgetId获取该AppWidget的信息了
//为当前所在进程申请一个新的appWidgetId
int newAppWidgetId = mAppWidgetHost.allocateAppWidgetId() ;
Log.i(TAG, "The new allocate appWidgetId is ----> " + newAppWidgetId) ;
//作为Intent附加值 ， 该appWidgetId将会与选定的AppWidget绑定
pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, newAppWidgetId) ;
//选择某项AppWidget后，立即返回，即回调onActivityResult()方法
startActivityForResult(pickIntent , MY_REQUEST_APPWIDGET) ;
}
});
}
// 如果
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
//直接返回，没有选择任何一项 ，例如按Back键
if(resultCode == RESULT_CANCELED)
return ;
switch(requestCode){
case MY_REQUEST_APPWIDGET :
Log.i(TAG, "MY_REQUEST_APPWIDGET intent info is -----> "+data ) ;
int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID , AppWidgetManager.INVALID_APPWIDGET_ID) ;
Log.i(TAG, "MY_REQUEST_APPWIDGET : appWidgetId is ----> " + appWidgetId) ;
//得到的为有效的id
if(appWidgetId != AppWidgetManager.INVALID_APPWIDGET_ID){
//查询指定appWidgetId的 AppWidgetProviderInfo对象 ， 即在xml文件配置的<appwidget-provider />节点信息
AppWidgetProviderInfo appWidgetProviderInfo = appWidgetManager.getAppWidgetInfo(appWidgetId) ;
//如果配置了configure属性 ， 即android:configure = "" ，需要再次启动该configure指定的类文件,通常为一个Activity
if(appWidgetProviderInfo.configure != null){
Log.i(TAG, "The AppWidgetProviderInfo configure info -----> " + appWidgetProviderInfo.configure ) ;
//配置此Action
Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE) ;
intent.setComponent(appWidgetProviderInfo.configure) ;
intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
startActivityForResult(intent , MY_CREATE_APPWIDGET) ;
}
else //直接创建一个AppWidget
onActivityResult(MY_CREATE_APPWIDGET , RESULT_OK , data) ; //参数不同，简单回调而已
}
break ;
case MY_CREATE_APPWIDGET:
completeAddAppWidget(data) ;
break ;
}
}
//向当前视图添加一个用户选择的
private void completeAddAppWidget(Intent data){
Bundle extra = data.getExtras() ;
int appWidgetId = extra.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID , -1) ;
//等同于上面的获取方式
//int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID , AppWidgetManager.INVALID_APPWIDGET_ID) ;
Log.i(TAG, "completeAddAppWidget : appWidgetId is ----> " + appWidgetId) ;
if(appWidgetId == -1){
Toast.makeText(MainActivity.this, "添加窗口小部件有误", Toast.LENGTH_SHORT) ;
return ;
}
AppWidgetProviderInfo appWidgetProviderInfo = appWidgetManager.getAppWidgetInfo(appWidgetId) ;
AppWidgetHostView hostView = mAppWidgetHost.createView(MainActivity.this, appWidgetId, appWidgetProviderInfo);
//linearLayout.addView(hostView) ;
int widget_minWidht = appWidgetProviderInfo.minWidth ;
int widget_minHeight = appWidgetProviderInfo.minHeight ;
//设置长宽 appWidgetProviderInfo 对象的 minWidth 和 minHeight 属性
LinearLayout.LayoutParams linearLayoutParams = new LinearLayout.LayoutParams(widget_minWidht, widget_minHeight);
//添加至LinearLayout父视图中
linearLayout.addView(hostView,linearLayoutParams) ;
}
}
大致流程如下：
1. 实例化AppWidgetHost， 具体实例化代码如下：
public AppWidgetHost(Context context, int hostId) {
this(context, hostId, null, context.getMainLooper());
}
/**
* @hide
*/
public AppWidgetHost(Context context, int hostId, OnClickHandler handler, Looper looper) {
mContext = context;
mHostId = hostId;
mOnClickHandler = handler;
mHandler = new UpdateHandler(looper);
mDisplayMetrics = context.getResources().getDisplayMetrics();
bindService();
}
该AppWidgetHost保存应用的Context对象，hostId，同时实例化一个Handler（和Launcher主线程共用一个MessageQueue），实例化一个IAppWidgetServer对象用于与AppWidgetService服务通信。
2. 通知AppWidgetService自身可以接收消息
/**
* Start receiving onAppWidgetChanged calls for your AppWidgets. Call this when your activity
* becomes visible, i.e. from onStart() in your Activity.
*/
public void startListening() {
Log.d(TAG, "startListening");
int[] updatedIds;
ArrayList<RemoteViews> updatedViews = new ArrayList<RemoteViews>();
final int userId = mContext.getUserId();
try {
if (mPackageName == null) {
mPackageName = mContext.getPackageName();
}
updatedIds = sService.startListening(
mCallbacks, mPackageName, mHostId, updatedViews, userId);
}
catch (RemoteException e) {
throw new RuntimeException("system server dead?", e);
}
final int N = updatedIds.length;
for (int i=0; i<N; i++) {
if (updatedViews.get(i) != null) {
updatedViews.get(i).setUser(new UserHandle(userId));
}
updateAppWidgetView(updatedIds[i], updatedViews.get(i), userId);
}
}
sService.startListening最终调用在AppWidgetServiceImpl中，
public int[] startListening(IAppWidgetHost callbacks, String packageName, int hostId,
List<RemoteViews> updatedViews) {
log("startListening");
if (!mHasFeature) {
return new int[0];
}
int callingUid = enforceCallingUid(packageName);
synchronized (mAppWidgetIds) {
ensureStateLoadedLocked();
Host host = lookupOrAddHostLocked(callingUid, packageName, hostId);
host.callbacks = callbacks;
updatedViews.clear();
ArrayList<AppWidgetId> instances = host.instances;
int N = instances.size();
int[] updatedIds = new int[N];
for (int i = 0; i < N; i++) {
AppWidgetId id = instances.get(i);
updatedIds[i] = id.appWidgetId;
updatedViews.add(cloneIfLocalBinder(id.views));
}
return updatedIds;
}
}
在AppWidgetService中mHost保存所有已注册的Host，此处会查找已经存在的或者添加一个新Host对象，同时记录AppWidgetHost的callback，更新updateViews列表为所有已添加到Host的插件的RemoteViews，最后返回该Host中所有插件的id。
appWidgetHost在取得自身所有已经添加的插件 id后，会先为对应的RemoteViews设定UserHandle，然后更新对应的AppWidgetHostView。
3. 获取新分配的appWidget id
/**
* Get a appWidgetId for a host in the calling process.
*
* @return a appWidgetId
*/
public int allocateAppWidgetId() {
try {
if (mPackageName == null) {
mPackageName = mContext.getPackageName();
}
return sService.allocateAppWidgetId(mPackageName, mHostId, mContext.getUserId());
}
catch (RemoteException e) {
throw new RuntimeException("system server dead?", e);
}
}AppWidgetServiceImpl会分配一个appWidget id，然后实例化一个AppWidgetId对象，保存到该Host和mAppWidgetIds中，同时也保存到xml文件中（缺少provider元素）。
4. bind appwidgetid
在上例代码中是通过发送intent的方式完成，当用户选择需要添加的widget后则会调用AppWidgetManager.bindAppWidgetIdIfAllowed(int appWidgetId, ComponentName provider, Bundle options) 方法，具体的实现在AppWidgetServiceImpl中
public boolean bindAppWidgetIdIfAllowed(
String packageName, int appWidgetId, ComponentName provider, Bundle options) {
if (!mHasFeature) {
return false;
}
try {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.BIND_APPWIDGET, null);
} catch (SecurityException se) {
if (!callerHasBindAppWidgetPermission(packageName)) {
return false;
}
}
bindAppWidgetIdImpl(appWidgetId, provider, options);
return true;
}
private void bindAppWidgetIdImpl(int appWidgetId, ComponentName provider, Bundle options) {
if (DBG) log("bindAppWidgetIdImpl appwid=" + appWidgetId
+ " provider=" + provider);
final long ident = Binder.clearCallingIdentity();
try {
synchronized (mAppWidgetIds) {
AppWidgetId id = lookupAppWidgetIdLocked(appWidgetId);
Provider p = lookupProviderLocked(provider);
// ...检查数据
id.provider = p;
id.options = options;
p.instances.add(id);
int instancesSize = p.instances.size();
if (instancesSize == 1) {
// tell the provider that it's ready
sendEnableIntentLocked(p);
}
// send an update now -- We need this update now, and just for this appWidgetId.
// It's less critical when the next one happens, so when we schedule the next one,
// we add updatePeriodMillis to its start time. That time will have some slop,
// but that's okay.
sendUpdateIntentLocked(p, new int[] { appWidgetId });
// schedule the future updates
registerForBroadcastsLocked(p, getAppWidgetIds(p));
saveStateAsync();
}
} finally {
Binder.restoreCallingIdentity(ident);
}
}
可以看到bindAppWidgetId主要是保存新Provider信息，同时发送enable和update广播通知应用Provider处理，最后将插件信息写入磁盘。
5. configure appWidget
此处略过
6. 显示appWidget
bind和configure成功后就可以显示appWidget到AppWidgetHostView中，整个添加过程结束。
AppWidgetProviderInfo appWidgetProviderInfo = appWidgetManager.getAppWidgetInfo(appWidgetId) ;
AppWidgetHostView hostView = mAppWidgetHost.createView(MainActivity.this, appWidgetId, appWidgetProviderInfo);
//linearLayout.addView(hostView) ;
int widget_minWidht = appWidgetProviderInfo.minWidth ;
int widget_minHeight = appWidgetProviderInfo.minHeight ;
//设置长宽 appWidgetProviderInfo 对象的 minWidth 和 minHeight 属性
LinearLayout.LayoutParams linearLayoutParams = new LinearLayout.LayoutParams(widget_minWidht, widget_minHeight);
//添加至LinearLayout父视图中
linearLayout.addView(hostView,linearLayoutParams) ;
下一篇再介绍createView的具体流程以及应用如何通知桌面来刷新数据。
前面的步骤3中有一个疑问：在AppWidgetServiceImpl中分配了一个widget id，同时保存了数据，但是如果后期用户后悔，取消添加插件会如何？基本做法应该为在接收到RESULT_CANCELED结果时通过AppWidgetHost删除已分配但是未添加的插件。