如何更新 Android 中前台服务的通知文本？

Question

我在 Android 中有一个前台服务设置。我想更新通知文本。我正在创建如下所示的服务。

如何更新此前台服务中设置的通知文本？更新通知的最佳做法是什么？任何示例代码将不胜感激。

public class NotificationService extends Service {

    private static final int ONGOING_NOTIFICATION = 1;

    private Notification notification;

    @Override
    public void onCreate() {
        super.onCreate();

        this.notification = new Notification(R.drawable.statusbar, getText(R.string.app_name), System.currentTimeMillis());
        Intent notificationIntent = new Intent(this, AbList.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
        this.notification.setLatestEventInfo(this, getText(R.string.app_name), "Update This Text", pendingIntent);

        startForeground(ONGOING_NOTIFICATION, this.notification);

    }

我正在我的主要活动中创建服务，如下所示：

    // Start Notification Service
    Intent serviceIntent = new Intent(this, NotificationService.class);
    startService(serviceIntent);

Answer 1

当你想更新startForeground()设置的Notification时，只需构建一个新的notification，然后使用NotificationManager来通知它。

关键点是使用相同的通知ID。

我没有测试重复调用startForeground()来更新Notification的场景，但我认为使用NotificationManager.notify会更好。

更新通知不会将服务从前台状态中删除（这只能通过调用 stopForground 来完成）；

示例：

private static final int NOTIF_ID=1;

@Override
public void onCreate (){
    this.startForeground();
}

private void startForeground() {
    startForeground(NOTIF_ID, getMyActivityNotification(""));
}

private Notification getMyActivityNotification(String text){
    // The PendingIntent to launch our activity if the user selects
    // this notification
    CharSequence title = getText(R.string.title_activity);
    PendingIntent contentIntent = PendingIntent.getActivity(this,
            0, new Intent(this, MyActivity.class), 0);

    return new Notification.Builder(this)
            .setContentTitle(title)
            .setContentText(text)
            .setSmallIcon(R.drawable.ic_launcher_b3)
            .setContentIntent(contentIntent).getNotification();     
}

/**
 * This is the method that can be called to update the Notification
 */
private void updateNotification() {
    String text = "Some text that will update the notification";

    Notification notification = getMyActivityNotification(text);

    NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    mNotificationManager.notify(NOTIF_ID, notification);
}

文档指出

要设置通知以便更新，请使用
通过调用 NotificationManager.notify() 来通知 ID。更新
发出此通知后，更新或创建
NotificationCompat.Builder 对象，从中构建一个 Notification 对象
并使用您之前使用的相同 ID 发出通知。
如果之前的通知仍然可见，系统会更新它
来自 Notification 对象的内容。如果之前的
通知已被驳回，已创建新通知
相反。

Answer 2

我认为使用相同的唯一 ID 和带有新信息的 Notification 再次调用 startForeground() 会起作用，尽管我还没有尝试过这种情况。

更新：根据评论，您应该使用 NotifcationManager 更新通知，并且您的服务继续保持在前台模式。看看下面的答案。

Answer 3

改进了 Android 8.0+ 中 Luca Manzo 的答案，更新通知时它将发出声音并显示为“平视”。
为了防止您需要添加 setOnlyAlertOnce(true)

所以代码是：

private static final int NOTIF_ID=1;

@Override
public void onCreate(){
        this.startForeground();
}

private void startForeground(){
        startForeground(NOTIF_ID,getMyActivityNotification(""));
}

private Notification getMyActivityNotification(String text){
        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.O){
        ((NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE)).createNotificationChannel(
        NotificationChannel("timer_notification","Timer Notification",NotificationManager.IMPORTANCE_HIGH))
}

        // The PendingIntent to launch our activity if the user selects
        // this notification
        PendingIntent contentIntent=PendingIntent.getActivity(this,
        0,new Intent(this,MyActivity.class),0);

        return new NotificationCompat.Builder(this,"my_channel_01")
        .setContentTitle("some title")
        .setContentText(text)
        .setOnlyAlertOnce(true) // so when data is updated don't make sound and alert in android 8.0+
        .setOngoing(true)
        .setSmallIcon(R.drawable.ic_launcher_b3)
        .setContentIntent(contentIntent)
        .build();
}

/**
 * This is the method that can be called to update the Notification
 */
private void updateNotification(){
        String text="Some text that will update the notification";

        Notification notification=getMyActivityNotification(text);

        NotificationManager mNotificationManager=(NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
        mNotificationManager.notify(NOTIF_ID,notification);
}

Answer 4

这是在您的服务中执行此操作的代码。创建一个新通知，但要求通知管理器通知您在 startForeground 中使用的相同通知 ID。

Notification notify = createNotification();
final NotificationManager notificationManager = (NotificationManager) getApplicationContext()
    .getSystemService(getApplicationContext().NOTIFICATION_SERVICE);

notificationManager.notify(ONGOING_NOTIFICATION, notify);

有关完整的示例代码，您可以在此处查看：

https ://github.com/plateaukao/AutoScreenOnOff/blob/master/src/com/danielkao/autoscreenonoff/SensorMonitorService.java

Answer 5

似乎现有的答案都没有显示如何处理完整的情况 - 如果是第一次调用，则启动Foreground，但更新后续调用的通知。

您可以使用以下模式来检测正确的情况：

private void notify(@NonNull String action) {
    boolean isForegroundNotificationVisible = false;
    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    StatusBarNotification[] notifications = notificationManager.getActiveNotifications();
    for (StatusBarNotification notification : notifications) {
        if (notification.getId() == FOREGROUND_NOTE_ID) {
            isForegroundNotificationVisible = true;
            break;
        }
    }
    Log.v(getClass().getSimpleName(), "Is foreground visible: " + isForegroundNotificationVisible);
    if (isForegroundNotificationVisible){
        notificationManager.notify(FOREGROUND_NOTE_ID, buildForegroundNotification(action));
    } else {
        startForeground(FOREGROUND_NOTE_ID, buildForegroundNotification(action));
    }
}

此外，您需要像其他答案中那样构建通知和通道：

private Notification buildForegroundNotification(@NonNull String action) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        createNotificationChannel();
    }
    //Do any customization you want here
    String title;
    if (ACTION_STOP.equals(action)) {
        title = getString(R.string.fg_notitifcation_title_stopping);
    } else {
        title = getString(R.string.fg_notitifcation_title_starting);
    }
    //then build the notification
    return new NotificationCompat.Builder(this, CHANNEL_ID)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle(title)
            .setOngoing(true)
            .build();
}

@RequiresApi(Build.VERSION_CODES.O)
private void createNotificationChannel(){
    NotificationChannel chan = new NotificationChannel(CHANNEL_ID, getString(R.string.fg_notification_channel), NotificationManager.IMPORTANCE_DEFAULT);
    chan.setLightColor(Color.RED);
    chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
    NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    assert manager != null;
    manager.createNotificationChannel(chan);
}