更改活动时避免线程重新启动

Question

Right now, when I change the activity, my thread seams to go to sleep or something. And when I come back to the main activity, there are two threads running, doing the same things. I'm not sure if this is the case, but it seems like it's something equal.

...
public class MainActivity extends Activity {

public static double cowCount = 195;
public static double income = 0.100;
static boolean twiceCow = false, Threadrunning = false;
...
public void inc() {
    new Thread(new income()).start();
}

class income implements Runnable {

    @Override
    public void run() {
        for (int i = 0; i < 20;) {
            final int value = i;
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            handler.post(new Runnable() {

                @Override
                public void run() {
                    cowCount = cowCount + income;
                    refresh();
                }
            });
        }
    }
}

This is how my thread looks like.

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    handler = new Handler();
    checkThread();
}

private void checkThread() {
    if (Threadrunning == false)
    inc();
    Threadrunning = true;
}
public void inc() {
    new Thread(new income()).start();
}
...
public void refresh () {
TextView myTextView = (TextView)findViewById(R.id.myText);
myTextView.setText("You Have " + String.valueOf((nf.format(cowCount)) + " Cows!"));
}

I don't really understand what I've done wrong.

Answer 1

Please review this post: http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html

Consider your activity re-start as the same thing as a config change.

This pattern, ie using a retained Fragment as a container for your thread, and proxying UI updates via callbacks to your activity, is a pattern that will work much better for you.

In your case you'd need only a single TaskCallback for your UI refresh(), eg onRefreshCowCount(int cows);