如何从 ForegroundService 中将应用程序带到前台

Question

我有一个

ForegroundService

需要一点时间才能运行。同时，用户可能会在应用程序运行时将其移至后台，例如按主页按钮或进入其他应用程序。当

ForegroundService

到达“触发器”时，它会尝试开始一个新的意图。如果应用程序在前台，这很好用，但如果它在后台，则不起作用。目标是当达到“触发器”时，应用程序将返回前台，以便用户可以在新意图中提供所需的输入。为了尝试这样做，我添加了标志

FLAG_ACTIVITY_NEW_TASK

和

FLAG_ACTIVITY_SINGLE_TOP

，因为它们看起来可以完成此操作。但是该应用程序不会返回到前台。这是可以做到的吗？

以下是有问题的代码的相关部分：

MainActivity.kt
...
private fun startService() {
    val serviceIntent = Intent(this, ForegroundService::class.java)
    ContextCompat.startForegroundService(this, serviceIntent)
}
...

ForegroundService.kt
...
//When trigger is reached, start the new activity and bring app to foreground if it was moved to background
private fun startNewActivity() {
    //First two lines are to shut down the foreground service since it has reached a trigger and is complete.
    super.onDestroy()
    stopSelf()
    //Start the new intent
    val startNewIntent = Intent(this, NewIntent:: class.java)
    startNewIntent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_SINGLE_TOP //Assumption was these flags would bring app to foreground
    startActivity(startNewIntent)
}
...

Answer 1

为了将意图注册到系统中，您需要使用

PendingIntent

而不是普通的

Intent

；当前台服务结束时（当你的触发器被触发时），你可以使用

send()

方法发送这个未决的意图

ForegroundService.kt
...
//When trigger is reached, start the new activity and bring app to foreground if it was moved to background
private fun startNewActivity() {
    //First two lines are to shut down the foreground service since it has reached a trigger and is complete.
    super.onDestroy()
    stopSelf()
    
    
    //Start the new intent

    val startNewIntent = Intent(this, NewIntent:: class.java)
    val pendingIntent = PendingIntent.getActivity(
        this, 0, startNewIntent,
        PendingIntent.FLAG_UPDATE_CURRENT
                or PendingIntent.FLAG_ONE_SHOT
    )
    
    try {
        pendingIntent.send()  // this should start `NewIntent` activity
    } catch (e: CanceledException) {
        e.printStackTrace()
    }   
    
}
... 

Answer 2

如果您使用的是android 10及以上版本，则需要申请

android.permission.SYSTEM_ALERT_WINDOW

权限。这些可以使用以下方式授予。

// Check if the permission is granted
if (Settings.canDrawOverlays(this)) {
    // Permission is granted, start your service
    startService(new Intent(this, FloatingViewService.class));
} else {
    // Permission is not granted, ask the user to enable it
    Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
            Uri.parse("package:" + getPackageName()));
    startActivityForResult(intent, REQUEST_CODE);
}

// Handle the result of the user's action
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_CODE) {
        // Check if the permission is granted
        if (Settings.canDrawOverlays(this)) {
            // Permission is granted, start your service
            startService(new Intent(this, FloatingViewService.class));
        } else {
            // Permission is denied, show a message
            Toast.makeText(this, "Please enable overlay permission", Toast.LENGTH_SHORT).show();
        }
    }
}

https://developer.android.com/reference/android/Manifest.permission#SYSTEM_ALERT_WINDOW