Android(安卓)开发之实时更新 App Widget
updatePeriodMills 定义了 Widget 的刷新频率,但是出于节约用户电量的考虑,Android 系统默认最小更新周期是 30 分钟,也就是说:如果您的程序需要实时更新数据,设置这个更新周期是 2 秒,那么您的程序是不会每隔 2 秒就收到更新通知的,而是要等到 30 分钟以上才可以,要想实时的更新 Widget,一般可以采用 Service 和 AlarmManager 对 Widget 进行更新。
利用 Service 更新 Widget
在 onUpdate() 方法中启动 Service:
public class MyWidgetProvider extends AppWidgetProvider { @Override public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { context.startService(new Intent(context, WidgetService.class)); }}
在 Service 中对 Widget 进行更新,这里 Service 利用 AlarmManager 每隔一段时间进行自启,防止 Service 被系统 Kill 掉后无法对 Widget 进行更新`
public class WidgetService extends Service { private static final int ALARM_DURATION = 5 * 60 * 1000; // service 自启间隔 private static final int UPDATE_DURATION = 10 * 1000; // Widget 更新间隔 private static final int UPDATE_MESSAGE = 1000; private UpdateHandler updateHandler; // 更新 Widget 的 Handler @Override public IBinder onBind(Intent intent) { return null; } @Override public int onStartCommand(Intent intent, int flags, int startId) { // 每个 ALARM_DURATION 自启一次 AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent alarmIntent = new Intent(getBaseContext(), WidgetService.class); PendingIntent pendingIntent = PendingIntent.getService(getBaseContext(), 0, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT); manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + ALARM_DURATION, pendingIntent); return START_STICKY; } @Override public void onCreate() { super.onCreate(); Message message = updateHandler.obtainMessage(); message.what = UPDATE_MESSAGE; updateHandler = new UpdateHandler(); updateHandler.sendMessageDelayed(message, UPDATE_DURATION); } private void updateWidget() { // 更新 Widget RemoteViews remoteViews = new RemoteViews(getApplicationContext().getPackageName(), R.layout.widget); AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context); appWidgetManager.updateAppWidget(new ComponentName(context, MyWidgetProvider.class), remoteViews); // 发送下次更新的消息 Message message = updateHandler.obtainMessage(); message.what = UPDATE_MESSAGE; updateHandler.sendMessageDelayed(message, UPDATE_DURATION); } protected final class UpdateHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case UPDATE_MESSAGE: updateWidget(); break; default: break; } } }}
Service + AlarmManager 更新 Widget
上面是利用 Service 的内部消息循环更新 Widget,也可以利用 AlarmManager 来定时触发更新。在 onUpdate() 中启动 Alarm,通过 AlarmManager 来循环启动 Service,剩下的原理基本就是一样的了。记得在 onDisabled() 取消掉 Alarm。
public class MyWidgetProvider extends AppWidgetProvider { private static final int UPDATE_DURATION = 10 * 1000; // Widget 更新间隔 private PendingIntent pendingIntent = null; @Override public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent alarmIntent = new Intent(getBaseContext(), WidgetService.class); if (pendingIntent == null) { pendingIntent = PendingIntent.getService(getBaseContext(), 0, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT); } manager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), UPDATE_DURATION, pendingIntent); } @Override public void onDisabled(Context context) { AlarmManager manager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE); manager.cancel(pendingIntent); }}
MyService 源码:
public class MyService extends Service{ @Override public int onStartCommand(Intent intent, int flags, int startId) { buildUpdate(); return super.onStartCommand(intent, flags, startId); } private void buildUpdate() { RemoteViews view = new RemoteViews(getPackageName(), R.layout.widget); RemoteViews remoteViews = new RemoteViews(getApplicationContext().getPackageName(), R.layout.widget); AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context); appWidgetManager.updateAppWidget(new ComponentName(context, MyWidgetProvider.class), remoteViews); }}
添加自定义 View
更新 Widget 是通过 RemoteViews 实现的,而 RemoteViews 支持的 View 有限,详细参考这里,如果想要在 Widget 中使用自定义 View,可以通过一下方式实现:
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);MyCustomView customView = new MyCustomView(context);customView.measure(width, height);customView.layout(0, 0, width, height);Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);customView.draw(new Canvas(bitmap));remoteViews.setImageViewBitmap(R.id.bitmap, bitmap);
实际上就是将自定义 View 在 Bitmap 上绘制,然后通过 ImageView 进行展现。
处理点击事件
RemoteViews 可以设置 setOnClickPendingIntent,通过 PendingIntent 来处理点击事件:
// 设置 button 事件为启动一个 ActivityIntent intent1 = new Intent("open_widget_activity");PendingIntent pendingIntent1 = PendingIntent.getActivity(context, 0, intent1, 0);remoteViews.setOnClickPendingIntent(R.id.button1, pendingIntent1);// 设置 button 事件为发送一个广播Intent intent2 = new Intent("send_broadcast");PendingIntent pendingIntent2 = PendingIntent.getBroadcast(context, 0, intent2, 0);remoteViews.setOnClickPendingIntent(R.id.button2, pendingIntent2);
然后需要处理事件的 Activity 或者 Receiver 接受对应的 Intent 即可。
转自:http://glgjing.github.io/
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