java - Android - 创建同步计时器

Question

我知道计时器的工作原理是让线程 hibernate x 时间，但我想知道是否有某种计时器不在 UI 线程之外的线程上运行。我考虑过使用一个循环来不断比较系统时间(以毫秒为单位)，但我想将其用作最后的手段，因为它似乎效率不高。

编辑:

堆栈跟踪:

07-25 14:38:38.037  22108-22124/com.example.myapp E/ViewRootImpl﹕ com.example.myapp.Main : Only the original thread that created a view hierarchy can touch its views.
java.lang.RuntimeException
        at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6355)
        at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:929)
        at android.view.ViewGroup.invalidateChildFast(ViewGroup.java:4466)
        at android.view.View.invalidateViewProperty(View.java:11112)
        at android.view.View.setTranslationY(View.java:10472)
        at android.view.View.setY(View.java:10400)
        at com.example.myapp.Player.update(Player.java:29)
        at com.example.myapp.Main.update(Main.java:70)
        at com.example.myapp.Main.access$000(Main.java:15)
        at com.example.myapp.Main$1.run(Main.java:33)
        at java.util.Timer$TimerImpl.run(Timer.java:284)

相关代码:

if (!onGround){

        playerVisual.setY(playerVisual.getY() + this.gravity);

    }

    if (playerVisual.getY() >= this.main.getDevice().getHeight() - 10){
        this.onGround = true;
    }
    else {
        this.onGround = false;
    }

如果您想知道的话，playerVisual 是一个 ImageView。

Answer 1

这是一个基于AsyncTask的解决方案:

class AsyncTimer extends AsyncTask<Void, Void, Void>
{
    boolean alive = true;
    long startMS;
    long intervalMS;
    MainActivity activity;

    public AsyncTimer(long startMS, long intervalMS, MainActivity activity)
    {
        this.startMS = startMS;
        this.intervalMS = intervalMS;
        this.activity = activity;
    }

    protected Void doInBackground(Void... params)
    {
        try
        {
            Thread.sleep(startMS);
        }
        catch (Exception e)
        {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }

        while (alive)
        {
            try
            {
                alive = activity.updateUI();
                Thread.sleep(intervalMS);
            }
            catch (Exception e)
            {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
        }

        return null;
    }
}

在MainActivity中使用它:

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
...
        new AsyncTimer(0, 1000, this).execute();
    }

    public boolean updateUI()
    {
        Log.d("Timer", "tick");
...
        return true;
    }