单击时更改自定义通知中图像按钮的背景颜色

Question

我有一个包含四个图像按钮的自定义通知布局。

用户单击它们时，我需要更改图像按钮的背景颜色。

我需要用

ImageButton imgButton = (ImageButton) findViewById(R.id.recentAppButt);
imgButton.setBackgroundColor(Color.BLUE);

但这会引起nullpointerexception错误，因为编译器找不到自定义通知布局中的最近使用的图像按钮，因为这些图像按钮在自定义通知布局中。

这是来自mainActivity.class的一些代码，我在其中创建或删除通知

private void createNotificationIcons() {
    String ns = Context.NOTIFICATION_SERVICE;
    notificationManager = (NotificationManager) getSystemService(ns);

    notification = new NotificationCompat.Builder(this)
            .setSmallIcon(R.drawable.home)
            .setContentTitle("My notification")
            .setContentText("All Buttons!")
            .setOngoing(true) /** notification will appear as ongoing notification*/
            .build();                      
    /** set a custom layout to the notification in notification drawer  */
    RemoteViews notificationView = new RemoteViews(getPackageName(), R.layout.notification);
    notification.contentView = notificationView;

    Intent recentAppIntent = new Intent(Context.NOTIFICATION_SERVICE);
    recentAppIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    Bundle recentAppBundle = new Bundle();   
    recentAppBundle.putInt("userAnswer", 1);
    recentAppIntent.putExtras(recentAppBundle);
    PendingIntent pendingrecentAppIntent = PendingIntent.getBroadcast(getBaseContext(), 1, recentAppIntent, 0);
    notificationView.setOnClickPendingIntent(R.id.recentAppButt, pendingrecentAppIntent);

    notificationManager.notify(1, notification);
}


public class SwitchButtonListener extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Bundle answerBundle = intent.getExtras();
        int userAnswer = answerBundle.getInt("userAnswer");
        if(userAnswer == 1) {
            ImageButton imgButton = (ImageButton) findViewById(R.id.recentAppButt);
            imgButton.setBackgroundColor(Color.BLUE);
            Toast.makeText(context, "Recent Apps", Toast.LENGTH_SHORT).show();
            Log.d("Recent", "recent app butt clicked");
            openRecentApps();
        }
    }
}

public class BackgroundService extends Service {

    MainActivity mainActivity = new MainActivity();
    MainActivity.SwitchButtonListener switchButtonListener = mainActivity.new   SwitchButtonListener();

    /** Called when the service is being created. */
    @Override
    public void onCreate() {
        super.onCreate();
    }

    /** The service is starting, due to a call to startService() */
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        registerReceiver(switchButtonListener, new     IntentFilter(Context.NOTIFICATION_SERVICE));
    return START_STICKY;
}

    /** Called when The service is no longer used and is being destroyed */
    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterReceiver(switchButtonListener);
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

这是notification.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
style="@android:style/TextAppearance.StatusBar.EventContent"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/transparent" >

<!-- create home button in notification drawer -->

<ImageButton
    android:id="@+id/homeButt"
    android:layout_width="79dp"
    android:layout_height="79dp"
    android:layout_marginLeft="1dp"
    android:background="@android:color/transparent"
    android:contentDescription="@string/discription"
    android:src="@drawable/home" />

<!-- create recent apps button in notification drawer -->

<ImageButton
    android:id="@+id/recentAppButt"
    android:layout_width="79dp"
    android:layout_height="79dp"
    android:background="@android:color/transparent"
    android:contentDescription="@string/discription"
    android:src="@drawable/recent" />

<!-- create lock screen button in notification drawer -->

<ImageButton
    android:id="@+id/lockScreenButt"
    android:layout_width="79dp"
    android:layout_height="79dp"
    android:background="@android:color/transparent"
    android:contentDescription="@string/discription"
    android:src="@drawable/lock" />

<!-- create allButtons button in notification drawer -->

<ImageButton
    android:id="@+id/allButtonsButt"
    android:layout_width="79dp"
    android:layout_height="79dp"
    android:background="#FF990000"
    android:contentDescription="@string/discription"
    android:src="@drawable/all_buttons" />

提前致谢。

Answer 1

检查布局文件中的ImageView是否具有将height和width的参数设置为wrap_parent 。

如果其中任何一个（layout_height或layout_width）设置为wrap_content ，并且您在ImageView上没有设置实际图像，则将其高度设置为0。换句话说，您应该将wrap_content更改为另一个值，例如以100dp为例，看看颜色是否改变。

Answer 2

findViewById是Activity类的一种方法，不适用于RemoteViews和通知。 您收到空值异常，因为R.id.recentAppButt在您的活动视图中不存在。

您可以通过在drawables文件夹中创建两个具有不同背景颜色的图标来实现所需的功能。 然后，可以使用RemoteViews类的setImageViewResource方法在两个图标之间切换，如下所示

notificationView.setImageViewResource(R.id.recentAppButt, R.drawable.icon_with_blue_background)

然后，您需要重建通知并通过NotificationManager重新通知 ，以便更新背景色。