一、 RemoteViews含义
RemoteViews:远程View
- 和远程Service一样，RemoteViews表示一个View的结构，可以在其他进程中显示。
- 由于它在其他进程中显示，为了能够更新它的界面，RemoteViews提供了一组基础的操作作用于跨进程更新它的界面。
- RemoteViews在Android中的使用场景有两种
- Notification通知栏
- 桌面小部件
二、 RemoteViews的基础概念
- PendingIntent
- 待定，即将发生的Intent
- 在将来的某个不确定的时刻发生，不同于Intent的立刻发生
- 典型使用场景是给RemoteViews添加点击事件，因为RemoteViews是在远程使用，没办法像其他View一样添加onClickLisenter事件
- 三种待定意图
- 启动Activity
- 启动Service
- 发送广播
三、 RemoteViews内部机制
- 应用中每调一次set方法，RemoteViews中就会添加一个对应的Action对象
- 用NotificationManager和AppWidgetManager来提交我们的更新时，Action对象就会传输到远程进程并在远程进程中依次执行
- 远程进程通过RemoteViews的apply方法来进行View的更新操作，RemoteViews的apply方法内部则会去遍历所有的Actions对象并调用
四、 RemoteViews实践
模拟的通知栏效果并实现跨进程的UI更新,逻辑如下：
- 有A,B 2个Activity分别运行在不同的进程中，一个A(MainActivity),一个B(ClientActivity)
- A接受通知，模拟通知栏的效果
- B可以不停的地发送通知栏消息（模拟消息）。通知方案选用Broadcast（系统是用Binder）
核心Code:
=== B send msg ===
public void onButtonClick(View v) {
RemoteViews remoteViews = new RemoteViews(getPackageName(), R.layout.layout_simulated_notification);
DateFormat df = new SimpleDateFormat("HH:mm:ss");
remoteViews.setTextViewText(R.id.msg, "msg from process : " + Process.myPid() + "\r\n"
+ df.format(new Date())
+ "\r\n点击开启B");
// set pending intent, when click textview
PendingIntent openActivityPendingIntent = PendingIntent.getActivity(
this, 0, new Intent(this, ClientActivity.class), PendingIntent.FLAG_UPDATE_CURRENT);
remoteViews.setOnClickPendingIntent(R.id.notify_layout, openActivityPendingIntent);
Intent intent = new Intent(Const.REMOTE_ACTION);
intent.putExtra(Const.EXTRA_REMOTE_VIEWS, remoteViews);
sendBroadcast(intent);
finish();
}
=== A receive ===
// receive remote view broadcast and update ui
private LinearLayout mRemoteViewsContent;
private BroadcastReceiver mRemoteViewsReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
RemoteViews remoteViews = intent
.getParcelableExtra(Const.EXTRA_REMOTE_VIEWS);
if (remoteViews != null) {
updateUI(remoteViews);
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
mRemoteViewsContent = (LinearLayout) findViewById(R.id.remote_views_content);
IntentFilter filter = new IntentFilter(Const.REMOTE_ACTION);
registerReceiver(mRemoteViewsReceiver, filter);
TextView hint = (TextView) findViewById(R.id.hint);
hint.setText("logic:\r\n"
+ "1. 有A，B 2个Activity运行在不同的进程\r\nA(MainActivity),B(ClientActivity)\r\n"
+ "2. A接受通知，模拟通知栏的效果。\r\n"
+ "3. B不停的地发送通知栏消息（模拟消息）\r\n\r\n"
+ "MainActivity（A) process : " + Process.myPid());
}
private void updateUI(RemoteViews remoteViews) {
// if A,B belongs to the same application use this way
// View view = remoteViews.apply(this, mRemoteViewsContent);
// if A,B belongs to different application,you may use this way
int layoutId = getResources().getIdentifier("layout_simulated_notification", "layout", getPackageName());
View view = getLayoutInflater().inflate(layoutId, mRemoteViewsContent, false);
remoteViews.reapply(this, view);
mRemoteViewsContent.addView(view);
}