RemoteViews在桌面小部件和通知栏的使用

（《Android开发艺术探索》读书笔记）

什么是RemoteViews：
它所表示的是一个View结构，可以在其他进程中显示，也就是可以跨进程更新它的界面。
RemoteViews的应用场景：
通知栏和桌面小部件（都运行在系统的SystemServer进程）。

首先说明桌面小部件的开发步骤：

1、定义小部件界面：
/桌面小部件/res/layout/widget.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <ImageView        android:id="@+id/iv_img"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:src="@drawable/ic_launcher" /></LinearLayout>

2、定义小部件配置信息：
/桌面小部件/res/xml/appwidget_provider_info.xml

<?xml version="1.0" encoding="utf-8"?><appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"    android:initialLayout="@layout/widget"    android:minHeight="84dp"    android:minWidth="84dp"    android:updatePeriodMillis="86400000" ></appwidget-provider>

3、定义小部件的实现类：
/桌面小部件/src/com/example/remoteviews/MyAppWidgetProvider.java

/** * 桌面小部件演示 * @author Administrator * */public class MyAppWidgetProvider extends AppWidgetProvider {    public static final String TAG = "MyAppWidgetProvider";    public static final String CLICK_ACTION = "com.example.remoteviews";    public MyAppWidgetProvider() {        super();    }    @Override    public void onEnabled(Context context) {        super.onEnabled(context);        Toast.makeText(context, "第一次添加小部件会调用我", Toast.LENGTH_SHORT).show();    }    @Override    public void onDisabled(Context context) {        super.onDisabled(context);        Toast.makeText(context, "最后一个小部件已被删除！", Toast.LENGTH_SHORT).show();    }    @Override    public void onDeleted(Context context, int[] appWidgetIds) {        super.onDeleted(context, appWidgetIds);        Toast.makeText(context, "小部件已被删除！", Toast.LENGTH_SHORT).show();    }    @Override    public void onReceive(final Context context, Intent intent) {        super.onReceive(context, intent);        Log.i(TAG, "onReceive:action=" + intent.getAction());        // 这里判断自己的action，做自己的事情        if (intent.getAction().equals(CLICK_ACTION)) {            Toast.makeText(context, "我在旋转", Toast.LENGTH_SHORT).show();            new Thread(new Runnable() {                @Override                public void run() {                    Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(),                            R.drawable.ic_launcher);                    AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);                    for (int i = 0; i < 37; i++) {                        float degree = (i * 10) % 360;                        RemoteViews remoteViews = new RemoteViews(context.getPackageName(),                                R.layout.widget);                        remoteViews.setImageViewBitmap(R.id.iv_img,                                rotateBitmap(context, bitmap, degree));                        Intent intent = new Intent();                        intent.setAction(CLICK_ACTION);                        PendingIntent pendingIntent = PendingIntent.getBroadcast(                                context, 0, intent, 0);                        remoteViews.setOnClickPendingIntent(R.id.iv_img, pendingIntent);                        appWidgetManager.updateAppWidget(                                new ComponentName(context, MyAppWidgetProvider.class), remoteViews);                        SystemClock.sleep(30);                    }                }            }).start();        }    }    /**     * 每次桌面小部件更新时都调用一次该方法     */    @Override    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {        super.onUpdate(context, appWidgetManager, appWidgetIds);        Toast.makeText(context, "每次更新小部件会调用我！", Toast.LENGTH_SHORT).show();        final int counter = appWidgetIds.length;        Log.i(TAG, "counter = "+ counter);        for (int i = 0; i < counter; i++) {            int appWidgetId = appWidgetIds[i];            onWidgetUpdate(context, appWidgetManager, appWidgetId);        }    }    /**     * 桌面小部件更新     * @param context     * @param appWidgetManager     * @param appWidgetId     */    private void onWidgetUpdate(Context context, AppWidgetManager appWidgetManager, int appWidgetId) {        Log.i(TAG, "appWidgetId = " + appWidgetId);        RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);        // 桌面小部件单击事件发送的Intent广播        Intent intent = new Intent();        intent.setAction(CLICK_ACTION);        PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, 0);        remoteViews.setOnClickPendingIntent(R.id.iv_img, pendingIntent);        appWidgetManager.updateAppWidget(appWidgetId, remoteViews);    }    /**     * 旋转     * @param context     * @param bitmap     * @param degree     * @return     */    private Bitmap rotateBitmap(Context context, Bitmap bitmap, float degree) {        Matrix matrix = new Matrix();        matrix.reset();        matrix.setRotate(degree);        Bitmap tmpBitmap = Bitmap.createBitmap(bitmap, 0, 0,                bitmap.getWidth(), bitmap.getHeight(),                matrix, true);        return tmpBitmap;    }}

4、在AndroidManifest.xml中声明小部件：

        <receiver android:name=".MyAppWidgetProvider" >            <meta-data                android:name="android.appwidget.provider"                android:resource="@xml/appwidget_provider_info" />            <intent-filter>                <action android:name="com.example.remoteviews" />                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />            </intent-filter>        </receiver>

第一个action用于识别小部件的单击行为；
第二个action作为小部件的标识必须存在，这是系统的规范。

运行后，在主界面添加桌面小部件，点击后会发现小部件旋转一周。
重复添加后就特别壮观：

然后说明RemoteViews在通知栏上的应用：
系统默认的通知：

        Notification notification = new Notification();        notification.icon = R.drawable.ic_launcher;        notification.tickerText = "hello world";        notification.when = System.currentTimeMillis();        notification.flags = Notification.FLAG_AUTO_CANCEL;        Intent intent = new Intent(this, MainActivity.class);        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);        notification.setLatestEventInfo(this, "标题", "内容", pendingIntent);        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);        manager.notify(1, notification);

上述代码会弹出一个系统默认样式的通知，点击后会清除本身。

使用RemoteViews实现自定义通知：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="horizontal" >    <TextView        android:id="@+id/tv_text"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="TextView"        android:textSize="25sp" />    <ImageView        android:id="@+id/iv_img"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:src="@drawable/ic_launcher" /></LinearLayout>

代码实现：

        Notification notification = new Notification();        notification.icon = R.drawable.ic_launcher;        notification.tickerText = "hello world";        notification.when = System.currentTimeMillis();        notification.flags = Notification.FLAG_AUTO_CANCEL;        Intent intent = new Intent(this, MainActivity.class);        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);        RemoteViews remoteViews = new RemoteViews(getPackageName(), R.layout.my_notification);        remoteViews.setTextViewText(R.id.tv_text, "自定义通知栏");        remoteViews.setImageViewResource(R.id.iv_img, R.drawable.ic_launcher);        PendingIntent pendingIntent2 = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);        remoteViews.setOnClickPendingIntent(R.id.tv_text, pendingIntent2);        notification.contentView = remoteViews;        notification.contentIntent = pendingIntent;        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);        manager.notify(2, notification);

RemoteViews所支持的View类型：
Layout: FrameLayout、RelativeLayout、LinearLaout、GridLayout
View: AnalogClock、Button、Chronometer、ImageButton、ImageView、ProgressBar、TextView、ViewFlipper、ListView、GridView、StackView、AdapterViewFlipper、ViewStub。