用于重复任务的 Android 处理程序 - 它会重叠吗？ 定时器任务 VS 处理程序 VS 警报管理器

Question

I'm trying to build an Android app which will repeatedly run some process every 10 mins. As I found out Handlers are more reliable than timers or scheduling. So I'm going to develop my app using the Handlers using the given below codes.

I'm little bit concerned that the below codes will create separate Handlers at each time I start the app and keep them running parallel, may be since I'm creating the Handler on onCreate .

So what is the best way to keep only a single Handler runs in background at a time?

private Handler handler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    handler = new Handler(); // new handler
    handler.postDelayed(runnable, 1000*60*10); // 10 mins int.
    setContentView(R.layout.activity_pro__sms);
} 

private Runnable runnable = new Runnable() {
    @Override
    public void run() {
        /* my set of codes for repeated work */
        foobar();
        handler.postDelayed(this, 1000*60*10); // reschedule the handler
    }
};

Answer 1

You can extend Application class and do your work in it.

public class App extends Application {

    private Handler handler;

    @Override
    protected void onCreate() {
        super.onCreate();
        handler = new Handler(); // new handler
        handler.postDelayed(runnable, 1000*60*10); // 10 mins int.
        setContentView(R.layout.activity_pro__sms);
    } 

    private Runnable runnable = new Runnable() {
        @Override
        public void run() {
            /* my set of codes for repeated work */
            foobar();
            handler.postDelayed(this, 1000*60*10); // reschedule the handler
        }
    };
}

And declare your class in manifest:

<application android:name=".App">

Edited

But it will work only if your app is running, otherwise you can use AlarmManager .

Answer 2

I decided to answer my own question since I've found out how to do it right way. The Android way. First of all what I was trying to do and posted in the question is a wrong approach to my requirement. Now I'm posting this so someone else will not do it wrong way but the following way.

Android has few options for timing.

1. Timer-task -> runs while application is alive. best for short term timing. Resource usage is higher.

2. Handler -> runs while application is alive. But not suitable to used as a scheduler. (this is what I've asked and it's not the correct way to do that). Handlers are the best way to do something repeatedly till the app is killed.

3. Alarm-manager -> The best way to schedule something to happen in future even if the app is killed. (this is what I should apply for my app).

This is what I figured out. Correct me if I'm wrong.

Answer 3

first define an utility class

public abstract class HandlerPeriodRunnable implements Runnable {

    private Handler periodHandler;
    private int msPeriod;

    public HandlerPeriodRunnable(Handler periodHandler, int msPeriod) {
        this.periodHandler = periodHandler;
        this.msPeriod = msPeriod;
    }

    @Override
    public void run() {
        periodRun();
        if (msPeriod > 0) {
            periodHandler.postDelayed(this, msPeriod);
        }
    }

    abstract public void periodRun();
}

then use it

final Handler mUIHandler = new Handler();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mUIHandler.postDelayed(new HandlerPeriodRunnable(mUIHandler, 1000) {
        @Override
        public void periodRun() {

        }
    }, 2000);
}