检查我的应用程序是否在后台运行

Question

this question has been asked like a hundred times but all i could fine have the same answer using

getRunningAppProcesses()

which doesn't work properly on Lollipop

so it there a completely reliable way to know if my app is alive in the background?

Thank you

EDIT:

This's what i use to check if the app in the foreground:

the preferences used:

    public static void setStartingActivity(Context context, boolean isStartingActivity) {
        PreferenceManager.getDefaultSharedPreferences(context).edit().putBoolean("isStartingActivity", isStartingActivity).apply();
    }

    public static boolean isStartingActivity(Context context) {
        return PreferenceManager.getDefaultSharedPreferences(context).getBoolean("isStartingActivity", false);
    }

    public static void setAppRunningInForeground(Context context, boolean isRunning) {
        PreferenceManager.getDefaultSharedPreferences(context).edit().putBoolean("AppIsRunningInForeground", isRunning).apply();
    }

    public static boolean isAppRunningForeground(Context context) {
        return PreferenceManager.getDefaultSharedPreferences(context).getBoolean("AppIsRunningInForeground", false);
    }

starting the activity:

Utility.PreferencesManager.setStartingActivity(getApplicationContext(), true);
startActivity(new Intent(getApplicationContext(), MainActivity.class));

the onStop and onStart implementation:

@Override
protected void onStart() {
    super.onStart();
    Log.e("Debugging", "MainActivity onStart");
    Utility.PreferencesManager.setAppRunningInForeground(getApplicationContext(), true);
}

@Override
protected void onStop() {
    super.onStop();
    Log.e("Debugging", "MainActivity onStop");

    if (!Utility.PreferencesManager.isStartingActivity(getApplicationContext()))
        Utility.PreferencesManager.setAppRunningInForeground(getApplicationContext(), false);
    else
        Utility.PreferencesManager.setStartingActivity(getApplicationContext(), false);
}

Answer 1

Blocking syncs when the UI is around is not going to solve your problem, simply because the user may return to your UI while you are in the middle of a sync. You need to be able to handle this situation.

Avoiding syncs when the user has recently been in your UI, for some short value of "recently", may help reduce the odds that the user will return to your UI while the app is syncing.

Based on your comments, let's assume that your app consists of 1+ activities plus your sync adapter. When your sync adapter runs, you want to determine if the user has been in the UI recently for this process.

There are three possibilities:

1. The UI is in the foreground when the sync adapter runs

2. The UI is in the background when the sync adapter runs

3. There is no UI, as the last process that had your UI had been terminated, and your sync adapter is running in a fresh process with no UI bits

Off the cuff, to handle that, I would have a custom Application , with two boolean fields:

• areActivitiesCreated , which will be true if this process ever created an activity, false by default

• isInBackground , which will be true if the app is in the background, false otherwise

I would have the Application call registerActivityLifecycleCallbacks() , and set areActivitiesCreated to true in onActivityCreated of the callback.

I would have the Application override onTrimMemory() , and update isInBackground based on the passed-in trim level, setting it to false if the trim level is one of the TRIM_MEMORY_RUNNING_* values, or true otherwise.

Then, your sync adapter would go ahead and do its work if either areActivitiesCreated is false (meaning that you have no UI) or if isInBackground is true (meaning that you are not in the foreground).

This avoids the need to add code to all the activities to track this condition.