Widget用法

下面是xml/appwidget_info的内容，里面包含了这个widget程序的基本定义。

　　android:minWidth="294dip" //最小宽度

　　android:minHeight="72dip" //最小高度

　　android:updatePeriodMillis="0" //更新频率

　　android:initialLayout="@layout/album_appwidget"> //widget界面布局文件

　　整个设计还是十分清晰，这里我们就不再做过多的赘述。

　　public class MediaAppWidgetProvider extends AppWidgetProvider {

　　public static final String CMDAPPWIDGETUPDATE = "appwidgetupdate";

　　static final ComponentName THIS_APPWIDGET =

　　new ComponentName("com.android.music", "com.android.music.MediaAppWidgetProvider");

　　private static MediaAppWidgetProvider sInstance;

　　static synchronized MediaAppWidgetProvider getInstance() {

　　if (sInstance == null) {

　　sInstance = new MediaAppWidgetProvider();

　　}

　　return sInstance;

　　}

　　@Override

　　public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {

　　defaultAppWidget(context, appWidgetIds);

　　// 发送一个Intent广播给MediaPlaybackService以便立即更新

　　Intent updateIntent = new Intent(MediaPlaybackService.SERVICECMD);

　　updateIntent.putExtra(MediaPlaybackService.CMDNAME,MediaAppWidgetProvider.CMDAPPWIDGETUPDATE);

　　updateIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS, appWidgetIds);

　　updateIntent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);

　　context.sendBroadcast(updateIntent);

　　}

　　/*

　　* 初始化widget默认状态，如果服务没有运行，我们启动music的时候默认单击隐藏

　　*/

　　private void defaultAppWidget(Context context, int[] appWidgetIds) {

　　final Resources res = context.getResources();

　　final RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.album_appwidget);

　　views.setViewVisibility(R.id.title, View.GONE);

　　views.setTextViewText(R.id.artist, res.getText(R.string.emptyplaylist));

　　linkButtons(context, views, false /* 没有播放*/);

　　pushUpdate(context, appWidgetIds, views);

　　}

　　private void pushUpdate(Context context, int[] appWidgetIds, RemoteViews views) {

　　// 更新指定的列表

　　final AppWidgetManager gm = AppWidgetManager.getInstance(context);

　　if (appWidgetIds != null) {

　　gm.updateAppWidget(appWidgetIds, views);

　　} else {

　　gm.updateAppWidget(THIS_APPWIDGET, views);

　　}

　　}

　　/**

　　* Check against {@link AppWidgetManager} if there are any instances of this widget.

　　*/

　　private boolean hasInstances(Context context) {

　　AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);

　　int[] appWidgetIds = appWidgetManager.getAppWidgetIds(THIS_APPWIDGET);

　　return (appWidgetIds.length > 0);

　　}

　　/**

　　* Handle a change notification coming over from {@link MediaPlaybackService}

　　*/

　　void notifyChange(MediaPlaybackService service, String what) {

　　if (hasInstances(service)) {

　　if (MediaPlaybackService.PLAYBACK_COMPLETE.equals(what) ||

　　MediaPlaybackService.META_CHANGED.equals(what) ||

　　MediaPlaybackService.PLAYSTATE_CHANGED.equals(what)) {

　　performUpdate(service, null);

　　}

　　}

　　}

　　/**

　　* Update all active widget instances by pushing changes

　　*/

　　void performUpdate(MediaPlaybackService service, int[] appWidgetIds) {

　　final Resources res = service.getResources();

　　final RemoteViews views = new RemoteViews(service.getPackageName(), R.layout.album_appwidget);

　　final int track = service.getQueuePosition() + 1;

　　CharSequence titleName = service.getTrackName();

　　CharSequence artistName = service.getArtistName();

　　CharSequence errorState = null;

　　// Format title string with track number, or show SD card message

　　String status = Environment.getExternalStorageState();

　　if (status.equals(Environment.MEDIA_SHARED) ||

　　status.equals(Environment.MEDIA_UNMOUNTED)) {

　　errorState = res.getText(R.string.sdcard_busy_title);

　　} else if (status.equals(Environment.MEDIA_REMOVED)) {

　　errorState = res.getText(R.string.sdcard_missing_title);

　　} else if (titleName == null) {

　　errorState = res.getText(R.string.emptyplaylist);

　　}

　　if (errorState != null) {

　　// Show error state to user

　　views.setViewVisibility(R.id.title, View.GONE);

　　views.setTextViewText(R.id.artist, errorState);

　　} else {

　　// No error, so show normal titles

　　views.setViewVisibility(R.id.title, View.VISIBLE);

　　views.setTextViewText(R.id.title, titleName);

　　views.setTextViewText(R.id.artist, artistName);

　　}

　　// Set correct drawable for pause state

　　final boolean playing = service.isPlaying();

　　if (playing) {

　　views.setImageViewResource(R.id.control_play, R.drawable.appwidget_pause);

　　} else {

　　views.setImageViewResource(R.id.control_play, R.drawable.appwidget_play);

　　}

　　// Link actions buttons to intents

　　linkButtons(service, views, playing);

　　pushUpdate(service, appWidgetIds, views);

　　}

　　/**

　　* Link up various button actions using {@link PendingIntents}.

　　*

　　* @param playerActive True if player is active in background, which means

　　* widget click will launch {@link MediaPlaybackActivity},

　　* otherwise we launch {@link MusicBrowserActivity}.

　　*/

　　private void linkButtons(Context context, RemoteViews views, boolean playerActive) {

　　// Connect up various buttons and touch events

　　Intent intent;

　　PendingIntent pendingIntent;

　　final ComponentName serviceName = new ComponentName(context, MediaPlaybackService.class);

　　if (playerActive) {

　　intent = new Intent(context, MediaPlaybackActivity.class);

　　pendingIntent = PendingIntent.getActivity(context,

　　0 /* no requestCode */, intent, 0 /* no flags */);

　　views.setOnClickPendingIntent(R.id.album_appwidget, pendingIntent);

　　} else {

　　intent = new Intent(context, MusicBrowserActivity.class);

　　pendingIntent = PendingIntent.getActivity(context,

　　0 /* no requestCode */, intent, 0 /* no flags */);

　　views.setOnClickPendingIntent(R.id.album_appwidget, pendingIntent);

　　}

　　intent = new Intent(MediaPlaybackService.TOGGLEPAUSE_ACTION);

　　intent.setComponent(serviceName);

　　pendingIntent = PendingIntent.getService(context,

　　0 /* no requestCode */, intent, 0 /* no flags */);

　　views.setOnClickPendingIntent(R.id.control_play, pendingIntent);

　　intent = new Intent(MediaPlaybackService.NEXT_ACTION);

　　intent.setComponent(serviceName);

　　pendingIntent = PendingIntent.getService(context,

　　0 /* no requestCode */, intent, 0 /* no flags */);

　　views.setOnClickPendingIntent(R.id.control_next, pendingIntent);

　　}

　　}