Android中级——RemoteView

RemoteView

• RemoteView的应用
• • Notification
  • Widget
  • PendingIntent
• RemoteViews内部机制
• 模拟RemoteViews

RemoteView的应用

Notification

如下开启一个系统的通知栏，点击后跳转到某网页

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.baidu.com"));
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        NotificationChannel channel1 = new NotificationChannel("0", "channel1", NotificationManager.IMPORTANCE_LOW);
        manager.createNotificationChannel(channel1);

        Notification.Builder builder = new Notification.Builder(this, "0");
        builder.setSmallIcon(R.drawable.ic_launcher)
                .setLargeIcon(Icon.createWithResource(this, R.drawable.ic_launcher))
                .setContentTitle("Notification")
                .setContentText("Hello World")
                .setContentIntent(pendingIntent);
        manager.notify(1, builder.build());
    }
}

效果如下

若采用RemoteView，可以自定义通知栏的布局，notification.xml文件如下

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

    <TextView
        android:id="@+id/tv"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:gravity="center_vertical" />
</LinearLayout>

代码如下，可通过一系列set方法设置布局

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.baidu.com"));
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        NotificationChannel channel1 = new NotificationChannel("0", "channel1", NotificationManager.IMPORTANCE_LOW);
        manager.createNotificationChannel(channel1);

        RemoteViews remoteViews = new RemoteViews(getPackageName(), R.layout.notification);
        remoteViews.setTextViewText(R.id.tv, "Hello Android");
        remoteViews.setImageViewResource(R.id.iv, R.drawable.ic_launcher);
        remoteViews.setOnClickPendingIntent(R.id.root, pendingIntent);

        Notification.Builder builder = new Notification.Builder(this, "0");
        builder.setSmallIcon(R.drawable.ic_launcher)
                .setCustomContentView(remoteViews);
        manager.notify(1, builder.build());
    }
}

效果如下

Widget

res/layout下创建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">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />
</LinearLayout>

res/xml下创建appwidget_provider_info.xml，设置最小宽高、自动更新的周期（ms）

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

</appwidget-provider>

创建MyAppWidgetProvider，给小组件设置一个点击动画

• onEnable：第一次添加时调用，可添加多次，但只在第一次调用

• onUpdate：添加或更新（周期时间到）时调用

• onDeleted：删除时调用

• onDisabled：最后一个小组件被删除时调用

• onReceive ：分发上面的事件

  public class MyAppWidgetProvider extends AppWidgetProvider {

    private static final String TAG = "MyAppWidgetProvider";
    public static final String CLICK_ACTION = "com.demo.demo0.MyAppWidgetProvider.CLICK";
  
    public MyAppWidgetProvider() {
        super();
    }
  
    @Override
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);
        String action = intent.getAction();
        Log.d(TAG, "onReceive: action = " + action);
        if (CLICK_ACTION.equals(action)) {
            Toast.makeText(context, "click", Toast.LENGTH_SHORT).show();
            new Thread(new Runnable() {
                @Override
                public void run() {
                    Bitmap srcBitmap = 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, rotateBitmap(context, srcBitmap, degree));
                        /*Intent clickIntent = new Intent();
                        clickIntent.setAction(CLICK_ACTION);
                        clickIntent.setComponent(new ComponentName(context, "com.demo.demo0.MyAppWidgetProvider"));
                        PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, clickIntent, 0);
                        remoteViews.setOnClickPendingIntent(R.id.iv, pendingIntent);*/
                        appWidgetManager.updateAppWidget(new ComponentName(context, MyAppWidgetProvider.class), remoteViews);
                        SystemClock.sleep(30);
                    }
                }
            }).start();
        }
    }
  
    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
        super.onUpdate(context, appWidgetManager, appWidgetIds);
        Log.d(TAG, "onUpdate: ");
        int count = appWidgetIds.length;
        Log.d(TAG, "onUpdate: count = " + count);
        for (int appWidgetId : appWidgetIds) {
            onWidgetUpdate(context, appWidgetManager, appWidgetId);
        }
    }
  
    private void onWidgetUpdate(Context context, AppWidgetManager appWidgetManager, int appWidgetId) {
        Log.d(TAG, "onWidgetUpdate: appWidgetId = " + appWidgetId);
        RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);
        Intent intentClick = new Intent();
        intentClick.setAction(CLICK_ACTION);
        intentClick.setComponent(new ComponentName(context, "com.demo.demo0.MyAppWidgetProvider"));
        PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intentClick, 0);
        remoteViews.setOnClickPendingIntent(R.id.iv, pendingIntent);
        appWidgetManager.updateAppWidget(appWidgetId, remoteViews);
    }
  
    private Bitmap rotateBitmap(Context context, Bitmap srcBitmap, float degree) {
        Matrix matrix = new Matrix();
        matrix.reset();
        matrix.setRotate(degree);
        return Bitmap.createBitmap(srcBitmap, 0, 0, srcBitmap.getWidth(), srcBitmap.getHeight(), matrix, true);
    }
  

  }

AppWidgetProvider本质是一个广播，需要在Manifest中注册，第二个Action是桌面组件的标识必须要加

<receiver
    android:name=".MyAppWidgetProvider">
    <meta-data
        android:name="android.appwidget.provider"
        android:resource="@xml/appwidget_provider_info" />

    <intent-filter>
        <action android:name="com.demo.demo0.MyAppWidgetProvider.CLICK" />
        <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
    </intent-filter>
</receiver>

PendingIntent

PendingIntent是在将来的某个不确定的时刻发生，而Intent是立刻发生

PendingIntent通过send和cancel方法发送和取消特定的Intent

• requesetCode一般情况下设为0
• 当ComponentName和intent-filter相同时，两个Intent相同
• 当Intent和requestCode相同时，两个PendingIntent相同

Flag常用的有：

• FLAG_ONE_SHOT：当前PendingIntent只能被调用一次，随后被自动cancel，后续send会调用失败。对于消息来说，后续通知和第一条通知保持一致，单击任一条通知后，其他无法再打开
• FLAG_NO_CREATE：当前PendingIntent不会主动创建，若之前不存在，则调用上面方法返回null
• FLAG_CANCEL_CURRENT：若当前PendingIntent已存在，则会被cancel并创建新的，被cancel的通知再点击无作用。对于消息来说，只有最新的才能打开
• FLAG_UPDATE_CURRENT：若当前PendingIntent已存在，则更新Intent中的Extra。对于消息来说，前面通知和最后一条通知保持一致，且都可以打开

RemoteViews内部机制

RemoteViews用于在其他进程中显示并更新UI，所支持的类型有

为避免每次对RemoteViews的操作都通过Binder传输，提供了Action封装对View的操作，如下

如对于setTextViewText()方法，传入对应操作的方法名

public void setTextViewText(int viewId, CharSequence text) {
    setCharSequence(viewId, "setText", text);
}

而在setCharSequence()中添加子类ReflectionAction

public void setCharSequence(int viewId, String methodName, CharSequence value) {
    addAction(new ReflectionAction(viewId, methodName, ReflectionAction.CHAR_SEQUENCE, value));
}

并将Action添加到ArrayList

private void addAction(Action a) {
    
    ......
    
    if (mActions == null) {
        mActions = new ArrayList<>();
    }
    mActions.add(a);
}

每当调用setxxx()方法时，并不会立即更新界面，而必须要通过NotificationManager的notify()或AppWidgetManager的updateAppWidget()，其内部会调用RemoteViews的

• apply()：加载布局并更新界面
• reApply()：只会更新界面

如下为AppWidgetHostView的updateAppWidget()方法

public void updateAppWidget(RemoteViews remoteViews) {
    applyRemoteViews(remoteViews, true);
}

protected void applyRemoteViews(RemoteViews remoteViews, boolean useAsyncIfPossible) {
   		......
        if (content == null && layoutId == mLayoutId) {
            try {
                remoteViews.reapply(mContext, mView, mOnClickHandler);
                content = mView;
                recycled = true;
                if (LOGD) Log.d(TAG, "was able to recycle existing layout");
            } catch (RuntimeException e) {
                exception = e;
            }
        }

        if (content == null) {
            try {
                content = remoteViews.apply(mContext, this, mOnClickHandler);
                if (LOGD) Log.d(TAG, "had to inflate new layout");
            } catch (RuntimeException e) {
                exception = e;
            }
        }
     	......
}

apply()方法通过inflateView()获取View返回

public View apply(Context context, ViewGroup parent, OnClickHandler handler) {
    RemoteViews rvToApply = getRemoteViewsToApply(context);
    View result = inflateView(context, rvToApply, parent);
    rvToApply.performApply(result, parent, handler);
    return result;
}

performApply()则是遍历调用Action的apply()方法

private void performApply(View v, ViewGroup parent, OnClickHandler handler) {
    if (mActions != null) {
        handler = handler == null ? DEFAULT_ON_CLICK_HANDLER : handler;
        final int count = mActions.size();
        for (int i = 0; i < count; i++) {
            Action a = mActions.get(i);
            a.apply(v, parent, handler);
        }
    }
}

再看子类ReflectionAction中apply()具体实现，可知其通过反射调用

@Override
public void apply(View root, ViewGroup rootParent, OnClickHandler handler) {
    final View view = root.findViewById(viewId);
    if (view == null) return;
    Class<?> param = getParameterType();
    if (param == null) {
        throw new ActionException("bad type: " + this.type);
    }
    try {
        getMethod(view, this.methodName, param, false /* async */).invoke(view, this.value);
    } catch (Throwable ex) {
        throw new ActionException(ex);
    }
}

模拟RemoteViews

如下模拟在MainActivity中通过广播传递RemoteViews，修改SecondActivity中的布局，manifest如下

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.demo.demo0">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity
            android:name=".SecondActivity"
            android:process=":remote">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity">

        </activity>
    </application>

</manifest>

MainActivity创建RemoteViews并发送广播

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        RemoteViews remoteViews = new RemoteViews(getPackageName(), R.layout.notification);

        remoteViews.setTextViewText(R.id.tv, "Hello RemoteViews");
        remoteViews.setImageViewResource(R.id.iv, R.drawable.ic_launcher);

        Intent remoteViewsIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.baidu.com"));
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, remoteViewsIntent, PendingIntent.FLAG_UPDATE_CURRENT);
        remoteViews.setOnClickPendingIntent(R.id.root, pendingIntent);

        Intent broadcastIntent = new Intent(SecondActivity.ACTION_REMOTE_VIEWS);
        broadcastIntent.putExtra(SecondActivity.EXTRA_REMOTE_VIEWS, remoteViews);
        sendBroadcast(broadcastIntent);
        finish();
    }
}

布局notification.xml如下

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

    <TextView
        android:id="@+id/tv"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:gravity="center_vertical" />
</LinearLayout>

SecondActivity接收广播获取RemoteViews，调用apply方法并把View添加到自身布局

public class SecondActivity extends AppCompatActivity {

    private static final String TAG = "SecondActivity";

    private LinearLayout mRemoteViesContainer;
    public static final String ACTION_REMOTE_VIEWS = "ACTION_REMOTE_VIEWS";
    public static final String EXTRA_REMOTE_VIEWS = "EXTRA_REMOTE_VIEWS";

    private BroadcastReceiver mRemoteViewsReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            RemoteViews remoteViews = intent.getParcelableExtra(EXTRA_REMOTE_VIEWS);
            if (remoteViews != null) {
                updateUI(remoteViews);
            }
        }
    };

    private void updateUI(RemoteViews remoteViews) {
        View view = remoteViews.apply(getApplicationContext(), mRemoteViesContainer);
        mRemoteViesContainer.addView(view);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        initView();
        startActivity(new Intent(this, MainActivity.class));
    }

    private void initView() {
        mRemoteViesContainer = findViewById(R.id.remote_views_container);
        IntentFilter intentFilter = new IntentFilter(ACTION_REMOTE_VIEWS);
        registerReceiver(mRemoteViewsReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(mRemoteViewsReceiver);
    }
}

SecondActivity布局为一个空的LinearLayout

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

</LinearLayout>