Question

我想每100毫秒或按下一个按钮时重复绘制一些东西。对于按钮onclick事件，它工作正常，但我不能使它在一个线程中工作。以下是代码：

的onclick

    button = (Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Draw();
        }
    });

螺纹

private Handler handler = new Handler();

private Runnable runnable = new Runnable()
{

    public void run()
    {
        Draw();
        handler.postDelayed(this, 1000);
    }
};

绘制方法

private void Draw(){

    Paint paint = new Paint();
    int i;

    Canvas canvas = holder.lockCanvas();

    // Dibujo el fondo
    paint.setColor(getResources().getColor(android.R.color.black));
    canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);

    holder.unlockCanvasAndPost(canvas);
}

Answer 1

这是因为UI线程单独运行到Runnable线程。像这样的单独线程无法进行交互。您将需要使用AsyncTask线程，这将使您能够定期访问UI线程。

例如：

private class ExampleThread extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {}

    @Override
    protected void doInBackground(Void... params) {
         while(!isCancelled()) { // Keep going until cancelled
             try {
                 Thread.sleep(100); // Delay 100 milliseconds
             } catch (InterruptedException e) {
                 Thread.interrupted();
             }
             publishProgress(); // Run onProgressUpdate() method
             if(isCancelled()) break; // Escape early if cancel() is called
         }

    }

    @Override
    protected void onPostExecute(Void... params) {}

    @Override
    protected void onProgressUpdate(Void... params) {
        // Here you can access the UI thread
        Draw();
    }
}

启动帖子：

ExampleThread thread = new ExampleThread();
thread.execute();

停止线程：

thread.cancel();

可以在this question上找到有关AsyncTask的更多信息和示例。

Android - 在线程上绘图

1 个答案: