android Widget添加过程和android添加widget不更新的问题分析解决

这两天在解一个关于widget的CR，由于之前也没有看过widget，借这个机会学习下widget，不过这个bug后来是另外一个同事fix的，这篇文章分为两部分：第一部分，分析android widget的添加过程，第二部分，分析该问题

第一部分： android widget 添加过程分析
Android中的AppWidget与google widget和中移动的widget并不是一个概念，这里的AppWidget只是把一个进程的控件嵌入到别外一个进程的窗口里的一种方法。View在另外一个进程里显示，但事件的处理方法还是在原来的进程里。这有点像 X Window中的嵌入式窗口。

首先，我们需要了解RemoteViews, AppWidgetHost, AppWidgetHostView等概念

RemoteViews：并不是一个真正的View，它没有实现View的接口，而只是一个用于描述View的实体。比如：创建View需要的资源ID和各个控件的事件响应方法。RemoteViews会通过进程间通信机制传递给AppWidgetHost。

AppWidgetHost

AppWidgetHost是真正容纳AppWidget的地方，它的主要功能有两个：

1 . 监听来自AppWidgetService的事件：

class Callbacks extends IAppWidgetHost.Stub
{
         public void updateAppWidget(int appWidgetId,RemoteViews views) { Message
               msg = mHandler.obtainMessage(HANDLE_UPDATE);
               msg.arg1 = appWidgetId;
               msg.obj = views; msg.sendToTarget();
         } //处理update事件，更新widget
         public void providerChanged(int appWidgetId,AppWidgetProviderInfo info) {
                   Message msg = mHandler.obtainMessage(HANDLE_PROVIDER_CHANGED);
         msg.arg1 = appWidgetId;
         msg.obj = info;
         msg.sendToTarget();
      }//处理providerChanged事件，更新widget
}

class UpdateHandler extends Handler {
        public UpdateHandler(Looper looper) { super(looper); }
        public void handleMessage(Message msg) {
               switch (msg.what) {
                        case HANDLE_UPDATE{
                               updateAppWidgetView(msg.arg1, (RemoteViews)msg.obj);
                               break;
                          }
                         case HANDLE_PROVIDER_CHANGED{
                              onProviderChanged(msg.arg1, (AppWidgetProviderInfo)msg.obj);
                                break;
                           }
                 }
         }
}

2 . 另外一个功能就是创建AppWidgetHostView。

前面我们说过RemoteViews不是真正的View，只是View的描述，而 AppWidgetHostView才是真正的View。这里先创建AppWidgetHostView，然后通过AppWidgetService查询 appWidgetId对应的RemoteViews，最后把RemoteViews传递给AppWidgetHostView去 updateAppWidget。

public final AppWidgetHostView createView(Context context, int appWidgetId, AppWidgetProviderInfo appWidget) {
        AppWidgetHostView view = onCreateView(context, appWidgetId, appWidget);
        view.setAppWidget(appWidgetId, appWidget);
         synchronized (mViews) { mViews.put(appWidgetId, view); }
         RemoteViews views = null;
         try {
              views = sService.getAppWidgetViews(appWidgetId);
   } catch(RemoteException e) {
               throw new RuntimeException("system server dead?", e);
        }
        view.updateAppWidget(views);
        return view;
}

AppWidgetHost其实是一个容器，在这个容器中可以放置widget，我们平常熟悉的Lanuch 就可以放置widget，所以lanuch应该是继承AppWidgetHost的

public class LauncherAppWidgetHost extends AppWidgetHost {
    public LauncherAppWidgetHost(Context context, int hostId) {
        super(context, hostId);
    }

    @Override
    protected AppWidgetHostView onCreateView(Context context, int appWidgetId,
            AppWidgetProviderInfo appWidget) {
        return new LauncherAppWidgetHostView(context);
    }
}

AppWidgetHostView

AppWidgetHostView是真正的View，但它只是一个容器，用来容纳实际的AppWidget的View。这个AppWidget的View是根据RemoteViews的描述来创建。这是在updateAppWidget里做的：

public void updateAppWidget(RemoteViews remoteViews){
   ...
   if (content == null && layoutId ==mLayoutId) {
   try {
        remoteViews.reapply(mContext, mView);
        content = mView;
        recycled = true;
        if(LOGD) Log.d(TAG, "was able to recycled existing layout");
   } catch (RuntimeException e) {
        exception= e;
    }
  }   // Try normal RemoteView inflation
   if (content == null) {
       try {
           content =remoteViews.apply(mContext, this);
           if (LOGD) Log.d(TAG, "had to inflate new layout");
        } catch(RuntimeException e) { exception = e; }
    }
    ...
if (!recycled) {
        prepareView(content);
        addView(content);
   }
   if (mView != content) {
         removeView(mView);
         mView = content;
    }
   ...
}

remoteViews.apply创建了实际的View，下面代码可以看出:

public View apply(Context context, ViewGroup parent) {
   View result = null;
       Context c =prepareContext(context);
       Resources r = c.getResources();
       LayoutInflater inflater =(LayoutInflater) c .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
       inflater =inflater.cloneInContext(c);
       inflater.setFilter(this);
       result = inflater.inflate(mLayoutId,parent, false);
       performApply(result);
       return result;
}

Host的实现者

AppWidgetHost和AppWidgetHostView是在框架中定义的两个基类。应用程序可以利用这两个类来实现自己的Host。Launcher是缺省的桌面，它是一个Host的实现者。

LauncherAppWidgetHostView扩展了AppWidgetHostView，实现了对长按事件的处理。

LauncherAppWidgetHost扩展了AppWidgetHost，这里只是重载了onCreateView，创建LauncherAppWidgetHostView的实例。

LauncherAppWidgetHostView: 扩展了AppWidgetHostView，实现了对长按事件的处理

LauncherAppWidgetHost: 扩展了AppWidgetHost，这里只是重载了onCreateView，创建LauncherAppWidgetHostView的实例

24 /** 25 * Specific {@link AppWidgetHost} that creates our {@link LauncherAppWidgetHostView} 26 * which correctly captures all long-press events. This ensures that users can 27 * always pick up and move widgets. 28 */ 29 public class LauncherAppWidgetHost extends AppWidgetHost { 30 public LauncherAppWidgetHost(Context context, int hostId) { 31 super(context, hostId); 32 } 33 34 @Override 35 protected AppWidgetHostView onCreateView(Context context, int appWidgetId, 36 AppWidgetProviderInfo appWidget) { 37 return new LauncherAppWidgetHostView(context); 38 } 39 }

首先在Launcher.java中定义了如下两个变量

174 private AppWidgetManager mAppWidgetManager; 175 private LauncherAppWidgetHost mAppWidgetHost;

在onCreate函数中初始化，

224 mAppWidgetManager = AppWidgetManager.getInstance(this); 225 mAppWidgetHost = new LauncherAppWidgetHost(this, APPWIDGET_HOST_ID); 226 mAppWidgetHost.startListening(); 上述代码，获取mAppWidgetManager的实例，并创建LauncherAppWidgetHost，以及监听 AppWidgetManager只是应用程序与底层Service之间的一个桥梁，是Android中标准的aidl实现方式应用程序通过AppWidgetManager调用Service中的方法 frameworks/base / core / java / android / appwidget / AppWidgetManager.java 35 /** 36 * Updates AppWidget state; gets information about installed AppWidget providers and other 37 * AppWidget related state. 38 */ 39 public class AppWidgetManager { 197 static WeakHashMap sManagerCache = new WeakHashMap(); 198 static IAppWidgetService sService; 204 /** 205 * Get the AppWidgetManager instance to use for the supplied {@link android.content.Context 206 * Context} object. 207 */ 208 public static AppWidgetManager getInstance(Context context) { 209 synchronized (sManagerCache) { 210 if (sService == null) { 211 IBinder b = ServiceManager.getService(Context.APPWIDGET_SERVICE); 212 sService = IAppWidgetService.Stub.asInterface(b); 213 } 214 215 WeakReference ref = sManagerCache.get(context); 216 AppWidgetManager result = null; 217 if (ref != null) { 218 result = ref.get(); 219 } 220 if (result == null) { 221 result = new AppWidgetManager(context); 222 sManagerCache.put(context, new WeakReference(result)); 223 } 224 return result; 225 } 226 } 227 228 private AppWidgetManager(Context context) { 229 mContext = context; 230 mDisplayMetrics = context.getResources().getDisplayMetrics(); 231 }

以上代码是设计模式中标准的单例模式

frameworks/base/ core / java / android / appwidget / AppWidgetHost.java

90 public AppWidgetHost(Context context, int hostId) { 91 mContext = context; 92 mHostId = hostId; 93 mHandler = new UpdateHandler(context.getMainLooper()); 94 synchronized (sServiceLock) { 95 if (sService == null) { 96 IBinder b = ServiceManager.getService(Context.APPWIDGET_SERVICE); 97 sService = IAppWidgetService.Stub.asInterface(b); 98 } 99 } 100 }

可以看到AppWidgetHost有自己的HostId，Handler，和sService

93 mHandler = new UpdateHandler(context.getMainLooper());

这是啥用法呢？

参数为Looper，即消息处理放到此Looper的MessageQueue中，有哪些消息呢？

40 static final int HANDLE_UPDATE = 1; 41 static final int HANDLE_PROVIDER_CHANGED = 2; 48 49 class Callbacks extends IAppWidgetHost.Stub { 50 public void updateAppWidget(int appWidgetId, RemoteViews views) { 51 Message msg = mHandler.obtainMessage(HANDLE_UPDATE); 52 msg.arg1 = appWidgetId; 53 msg.obj = views; 54 msg.sendToTarget(); 55 } 56 57 public void providerChanged(int appWidgetId, AppWidgetProviderInfo info) { 58 Message msg = mHandler.obtainMessage(HANDLE_PROVIDER_CHANGED); 59 msg.arg1 = appWidgetId; 60 msg.obj = info; 61 msg.sendToTarget(); 62 } 63 } 64 65 class UpdateHandler extends Handler { 66 public UpdateHandler(Looper looper) { 67 super(looper); 68 } 69 70 public void handleMessage(Message msg) { 71 switch (msg.what) { 72 case HANDLE_UPDATE: { 73 updateAppWidgetView(msg.arg1, (RemoteViews)msg.obj); 74 break; 75 } 76 case HANDLE_PROVIDER_CHANGED: { 77 onProviderChanged(msg.arg1, (AppWidgetProviderInfo)msg.obj); 78 break; 79 } 80 } 81 } 82 }

通过以上可以看到主要有两中类型的消息，HANDLE_UPDATE和HANDLE_PROVIDER_CHANGED

处理即通过自身定义的方法

231 /** 232 * Called when the AppWidget provider for a AppWidget has been upgraded to a new apk. 233 */ 234 protected void onProviderChanged(int appWidgetId, AppWidgetProviderInfo appWidget) { 235 AppWidgetHostView v; 236 synchronized (mViews) { 237 v = mViews.get(appWidgetId); 238 } 239 if (v != null) { 240 v.updateAppWidget(null, AppWidgetHostView.UPDATE_FLAGS_RESET); 241 } 242 } 243 244 void updateAppWidgetView(int appWidgetId, RemoteViews views) { 245 AppWidgetHostView v; 246 synchronized (mViews) { 247 v = mViews.get(appWidgetId); 248 } 249 if (v != null) { 250 v.updateAppWidget(views, 0); 251 } 252 }

那么此消息是何时由谁发送的呢？

从以上的代码中看到AppWidgetHost定义了内部类Callback，扩展了类IAppWidgetHost.Stub，类Callback中负责发送以上消息

Launcher中会调用本类中的如下方法，

102 /** 103 * Start receiving onAppWidgetChanged calls for your AppWidgets. Call this when your activity 104 * becomes visible, i.e. from onStart() in your Activity. 105 */ 106 public void startListening() { 107 int[] updatedIds; 108 ArrayList updatedViews = new ArrayList(); 109 110 try { 111 if (mPackageName == null) { 112 mPackageName = mContext.getPackageName(); 113 } 114 updatedIds = sService.startListening(mCallbacks, mPackageName, mHostId, updatedViews); 115 } 116 catch (RemoteException e) { 117 throw new RuntimeException("system server dead?", e); 118 } 119 120 final int N = updatedIds.length; 121 for (int i=0; i 当用户在Dialog中选择AddAdapter.ITEM_APPWIDGET时，首先会通过AppWidgethost分配一个appWidgetId，并最终调到AppWidgetService中去

同时发送Intent，其中保存有刚刚分配的appWidgetId，AppWidgetManager.EXTRA_APPWIDGET_ID

139 /** 140 * Get a appWidgetId for a host in the calling process. 141 * 142 * @return a appWidgetId 143 */ 144 public int allocateAppWidgetId() { 145 try { 146 if (mPackageName == null) { 147 mPackageName = mContext.getPackageName(); 148 } 149 return sService.allocateAppWidgetId(mPackageName, mHostId); 150 } 151 catch (RemoteException e) { 152 throw new RuntimeException("system server dead?", e); 153 } 154 } 2016 Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK); 2017 pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId); 2018 // start the pick activity 2019 startActivityForResult(pickIntent, REQUEST_PICK_APPWIDGET); 这段代码之后，代码将会怎么执行呢，根据Log信息，可以看到代码将会执行到Setting应用中 packages/apps/Settings/ src / com / android / settings / AppWidgetPickActivity.java 此类将会通过AppWidgetService获取到当前系统已经安装的Widget，并显示出来 78 /** 79 * Create list entries for any custom widgets requested through 80 * {@link AppWidgetManager#EXTRA_CUSTOM_INFO}. 81 */ 82 void putCustomAppWidgets(List items) { 83 final Bundle extras = getIntent().getExtras(); 84 85 // get and validate the extras they gave us 86 ArrayList customInfo = null; 87 ArrayList customExtras = null; 88 try_custom_items: { 89 customInfo = extras.getParcelableArrayList(AppWidgetManager.EXTRA_CUSTOM_INFO); 90 if (customInfo == null || customInfo.size() == 0) { 91 Log.i(TAG, "EXTRA_CUSTOM_INFO not present."); 92 break try_custom_items; 93 } 94 95 int customInfoSize = customInfo.size(); 96 for (int i=0; i/////下面这句话救了我，太感谢了 mAppWidgetManager.bindAppWidgetId(mAppWidgetId, intent.getComponent()); 如果此次添加的Widget是intent.getComponent()的第一个实例，将会发送如下广播 171 /** 172 * Sent when an instance of an AppWidget is added to a host for the first time. 173 * This broadcast is sent at boot time if there is a AppWidgetHost installed with 174 * an instance for this provider. 175 * 176 * @see AppWidgetProvider#onEnabled AppWidgetProvider.onEnabled(Context context) 177 */ 178 public static final String ACTION_APPWIDGET_ENABLED = "android.appwidget.action.APPWIDGET_ENABLED"; 紧接着会发送UPDATE广播 135 /** 136 * Sent when it is time to update your AppWidget. 137 * 138 *

This may be sent in response to a new instance for this AppWidget provider having 139 * been instantiated, the requested {@link AppWidgetProviderInfo#updatePeriodMillis update interval} 140 * having lapsed, or the system booting. 141 * 142 *

143 * The intent will contain the following extras: 144 *

145 * 146 * 147 * 150 * 151 *

{@link #EXTRA_APPWIDGET_IDS}

The appWidgetIds to update. This may be all of the AppWidgets created for this 148 * provider, or just a subset. The system tries to send updates for as few AppWidget 149 * instances as possible.

152 * 153 * @see AppWidgetProvider#onUpdate AppWidgetProvider.onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) 154 */ 155 public static final String ACTION_APPWIDGET_UPDATE = "android.appwidget.action.APPWIDGET_UPDATE";

待用户选择完要添加的widget之后，将会回到Launcher.java中的函数onActivityResult中

538 case REQUEST_PICK_APPWIDGET: 539 addAppWidget(data); 540 break;

上述addAppWidget中做了哪些事情呢？

1174 void addAppWidget(Intent data) { 1175 // TODO: catch bad widget exception when sent 1176 int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, -1); 1177 AppWidgetProviderInfo appWidget = mAppWidgetManager.getAppWidgetInfo(appWidgetId); 1178 1179 if (appWidget.configure != null) { 1180 // Launch over to configure widget, if needed 1181 Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE); 1182 intent.setComponent(appWidget.configure); 1183 intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId); 1184 1185 startActivityForResultSafely(intent, REQUEST_CREATE_APPWIDGET); 1186 } else { 1187 // Otherwise just add it 1188 onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data); 1189 } 1190 }

首先获取appWidgetId，再通过AppWidgetManager获取AppWidgetProviderInfo，最后判断此Widget是否存在ConfigActivity，如果存在则启动ConfigActivity，否则直接调用函数onActivityResult

541 case REQUEST_CREATE_APPWIDGET: 542 completeAddAppWidget(data, mAddItemCellInfo); 543 break;

通过函数completeAddAppWidget把此widget的信息插入到数据库中，并添加到桌面上

873 /** 874 * Add a widget to the workspace. 875 * 876 * @param data The intent describing the appWidgetId. 877 * @param cellInfo The position on screen where to create the widget. 878 */ 879 private void completeAddAppWidget(Intent data, CellLayout.CellInfo cellInfo) { 880 Bundle extras = data.getExtras(); 881 int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1); 882 883 if (LOGD) Log.d(TAG, "dumping extras content=" + extras.toString()); 884 885 AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId); 886 887 // Calculate the grid spans needed to fit this widget 888 CellLayout layout = (CellLayout) mWorkspace.getChildAt(cellInfo.screen); 889 int[] spans = layout.rectToCell(appWidgetInfo.minWidth, appWidgetInfo.minHeight); 890 891 // Try finding open space on Launcher screen 892 final int[] xy = mCellCoordinates; 893 if (!findSlot(cellInfo, xy, spans[0], spans[1])) { 894 if (appWidgetId != -1) mAppWidgetHost.deleteAppWidgetId(appWidgetId); 895 return; 896 } 897 898 // Build Launcher-specific widget info and save to database 899 LauncherAppWidgetInfo launcherInfo = new LauncherAppWidgetInfo(appWidgetId); 900 launcherInfo.spanX = spans[0]; 901 launcherInfo.spanY = spans[1]; 902 903 LauncherModel.addItemToDatabase(this, launcherInfo, 904 LauncherSettings.Favorites.CONTAINER_DESKTOP, 905 mWorkspace.getCurrentScreen(), xy[0], xy[1], false); 906 907 if (!mRestoring) { 908 mDesktopItems.add(launcherInfo); 909 910 // Perform actual inflation because we're live 911 launcherInfo.hostView = mAppWidgetHost.createView(this, appWidgetId, appWidgetInfo); 912 913 launcherInfo.hostView.setAppWidget(appWidgetId, appWidgetInfo); 914 launcherInfo.hostView.setTag(launcherInfo); 915 916 mWorkspace.addInCurrentScreen(launcherInfo.hostView, xy[0], xy[1], 917 launcherInfo.spanX, launcherInfo.spanY, isWorkspaceLocked()); 918 } 919 }

Launcher中删除widget

长按一个widget，并拖入到DeleteZone中可实现删除

具体代码在DeleteZone中

92 public void onDrop(DragSource source, int x, int y, int xOffset, int yOffset, 93 DragView dragView, Object dragInfo) { 94 final ItemInfo item = (ItemInfo) dragInfo; 95 96 if (item.container == -1) return; 97 98 if (item.container == LauncherSettings.Favorites.CONTAINER_DESKTOP) { 99 if (item instanceof LauncherAppWidgetInfo) { 100 mLauncher.removeAppWidget((LauncherAppWidgetInfo) item); 101 } 102 } else { 103 if (source instanceof UserFolder) { 104 final UserFolder userFolder = (UserFolder) source; 105 final UserFolderInfo userFolderInfo = (UserFolderInfo) userFolder.getInfo(); 106 // Item must be a ShortcutInfo otherwise it couldn't have been in the folder 107 // in the first place. 108 userFolderInfo.remove((ShortcutInfo)item); 109 } 110 } 111 if (item instanceof UserFolderInfo) { 112 final UserFolderInfo userFolderInfo = (UserFolderInfo)item; 113 LauncherModel.deleteUserFolderContentsFromDatabase(mLauncher, userFolderInfo); 114 mLauncher.removeFolder(userFolderInfo); 115 } else if (item instanceof LauncherAppWidgetInfo) { 116 final LauncherAppWidgetInfo launcherAppWidgetInfo = (LauncherAppWidgetInfo) item; 117 final LauncherAppWidgetHost appWidgetHost = mLauncher.getAppWidgetHost(); 118 if (appWidgetHost != null) { 119 appWidgetHost.deleteAppWidgetId(launcherAppWidgetInfo.appWidgetId); 120 } 121 } 122 LauncherModel.deleteItemFromDatabase(mLauncher, item); 123 }

删除时，判断删除的类型是否是AppWidget，如果是的话，要通过AppWidgetHost，删除AppWidetId，并最终从数据库中删除。

第二部分：分析问题：
问题描述：在烧上新版本以及做完factory reset之后，概率性出现添加到桌面上的widget不更新的问题，如电量管理没有图片，但是功能不受影响，天气和时钟都不更新。

问题再现条件：手机插有sim卡 && 第一次开机或为恢复出产设置重启
问题再现概率：50%

原因：
由于手机第一次开机的时候，会有一个下面的启动流程：
Launcher启动->检测到sim卡->重启Launcher

上一个启动的Launcher的activity还没有退出的时候，新启的Launcher的activity已经起来了。
由于统一package的activity只能注册一个listener，新启动的activity在要注册listener时，
因为上一个启动的Launcher还没有完全退出，系统发现此listener已经存在，
所以直接就把前一个listener的引用传了出来。但那个已经存在的listener对新的activity来说只是昙花一现，
即将被上一个Launcher销毁掉，新的activity中的listener变为null，导致以后所有的widget更新消息都得不到处理。

对应方法：
只需要修改一行代码就能搞定。我这边测试了5次，基本确认没有问题。
请参考下面的diff结果修改Launcher2的AndroidManifest.xml文件：

diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 3706661..c92f502 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -75,7 +75,8 @@
             android:stateNotNeeded="true"
             android:theme="@style/Theme"
             android:screenOrientation="nosensor"
-            android:windowSoftInputMode="stateUnspecified|adjustPan">
+            android:windowSoftInputMode="stateUnspecified|adjustPan"
+            android:configChanges="mcc|mnc|keyboard|keyboardHidden|navigation|orientation|uiMode">

android:configChanges 如果配置了这个属性，当我们横竖屏切换的时候会直接调用onCreate方法中的onConfigurationChanged方法，而不会重新执行onCreate方法，那当然如果不配置这个属性的话就会重新调用onCreate方法了
转下这个属性的使用方式

通过设置这个属性可以使Activity捕捉设备状态变化，以下是可以被识别的内容：
CONFIG_FONT_SCALE
CONFIG_MCC
CONFIG_MNC
CONFIG_LOCALE
CONFIG_TOUCHSCREEN
CONFIG_KEYBOARD
CONFIG_NAVIGATION
CONFIG_ORIENTATION

设置方法：将下列字段用“|”符号分隔开，例如：“ locale|navigation|orientation
”

Value	Description
“mcc“	The IMSI mobile country code (MCC) has changed — that is, a SIM hasbeen detected and updated the MCC.移动国家号码，由三位数字组成，每个国家都有自己独立的MCC，可以识别手机用户所属国家。
“mnc“	The IMSI mobile network code (MNC) has changed — that is, a SIM hasbeen detected and updated the MNC.移动网号，在一个国家或者地区中，用于区分手机用户的服务商。
“locale“	The locale has changed — for example, the user has selected a new language that text should be displayed in.用户所在地区发生变化。
“touchscreen“	The touchscreen has changed. (This should never normally happen.)
“keyboard“	The keyboard type has changed — for example, the user has plugged in an external keyboard.键盘模式发生变化，例如：用户接入外部键盘输入。
“keyboardHidden“	The keyboard accessibility has changed — for example, the user has slid the keyboard out to expose it.用户打开手机硬件键盘
“navigation“	The navigation type has changed. (This should never normally happen.)
“orientation“	The screen orientation has changed — that is, the user has rotated the device.设备旋转，横向显示和竖向显示模式切换。
“fontScale“	The font scaling factor has changed — that is, the user has selected a new global font size.全局字体大小缩放发生改变

通过一个例子介绍这个属性的用法：首先需要修改项目的manifest:
? View Code XML

xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.androidres.ConfigChangedTesting"
   android:versionCode="1"
   android:versionName="1.0.0">
   android:icon="@drawable/icon"android:label="@string/app_name">
       android:name=".ConfigChangedTesting"
               android:label="@string/app_name"
               android:configChanges="keyboardHidden|orientation">
         >
               android:name="android.intent.action.MAIN" />
               android:name="android.intent.category.LAUNCHER" />
         >
      >
  >
>

在Activity中添加了 android:configChanges属性，目的是当所指定属性(Configuration Changes)发生改变时，通知程序调用 onConfigurationChanged()函数。创建一个Layout UI:
? View Code XML

xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >

  android:id="@+id/pick"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="Pick"
  />

  android:id="@+id/view"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="View"
  />
>

这个简单的UI包含两个按钮，其中一个是通过Contact列表选择一个联系人，另外一个是查看当前选择联系人的详细内容。

项目的Java源代码：
01.import android.app.Activity;
02.import android.content.Intent;
03.import android.content.res.Configuration;
04.import android.net.Uri;
05.import android.os.Bundle;
06.import android.provider.Contacts.People;
07.import android.view.View;
08.import android.widget.Button;
09.

10.public class ConfigChangedTesting extends Activity {
11. /** Called when the activity is first created. */
12. static final int PICK_REQUEST = 1337;
13. Button viewButton=null;
14. Uri contact = null;
15. @Override
16. public void onCreate(Bundle savedInstanceState) {
17.       super.onCreate(savedInstanceState);
18.       //setContentView(R.layout.main);
19.

20.       setupViews();
21. }
22.

23. public void onConfigurationChanged(Configuration newConfig) {
24.                super.onConfigurationChanged(newConfig);
25.

26.                setupViews();
27. }
28.

29. /* (non-Javadoc)
30.    * @see android.app.Activity#onActivityResult(int, int, android.content.Intent)
31.    */
32. @Override
33. protected void onActivityResult(int requestCode, int resultCode, Intent data) {
34.       // TODO Auto-generated method stub
35.       //super.onActivityResult(requestCode, resultCode, data);
36.

37.       if(requestCode == PICK_REQUEST){
38.

39.          if(resultCode==RESULT_OK){
40.

41.             contact = data.getData();
42.             viewButton.setEnabled(true);
43.          }
44.

45.       }
46.

47. }
48.

49. private void setupViews(){
50.

51.       setContentView(R.layout.main);
52.

53.       Button pickBtn = (Button)findViewById(R.id.pick);
54.

55.       pickBtn.setOnClickListener(new View.OnClickListener(){
56.

57.          public void onClick(View v) {
58.             // TODO Auto-generated method stub
59.

60.             Intent i=new Intent(Intent.ACTION_PICK,People.CONTENT_URI);
61.             startActivityForResult(i,PICK_REQUEST);
62.          }
63.       });
64.

65.       viewButton =(Button)findViewById(R.id.view);
66.

67.       viewButton.setOnClickListener(new View.OnClickListener() {
68.                   public void onClick(View view) {
69.                      startActivity(new Intent(Intent.ACTION_VIEW, contact));
70.                   }
71.       });
72.

73.       viewButton.setEnabled(contact!=null);
74. }

75.}

转载自：

http://blog.163.com/dengjingniurou@126/blog/static/53989196201201910154151/

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