我被困在AsyncTask中的onBackPressed()上

Question

我开始研究Asynctask Demo.我想要的是,"当我按下Android设备中的后退按钮时,我想停止在应用程序中运行的任务"

我在onBackPressed()方法上设置了这个东西但是之后在Logcat任务中没有停止.

我在哪里弄错了,帮我解决这个问题？

public class Activity1 extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    new CountDownTask().execute();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}
@Override
public void onBackPressed() {
    super.onBackPressed();
    new CountDownTask().cancel(true);
}

private class CountDownTask extends AsyncTask<Void, Integer, Void>{
    @Override
    protected void onPreExecute() {
        TextView tvCounter = (TextView) findViewById(R.id.tv_counter);
        tvCounter.setText("START");
    }

    @Override
    protected Void doInBackground(Void... params) {
        for(int i=15;i>=0;i--){
            try {
                Thread.sleep(1000);
                publishProgress(i);
                Log.e("Aka", String.valueOf(i));
                if(isCancelled()){
                    break;
                }
            } catch (InterruptedException e) {
            }
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        TextView tvCounter = (TextView) findViewById(R.id.tv_counter);

        tvCounter.setText( Integer.toString(values[0].intValue()));         
    }

    @Override
    protected void onPostExecute(Void result) {
        TextView tvCounter = (TextView) findViewById(R.id.tv_counter);
        tvCounter.setText("DONE");          
    }       
}

}

Answer 1

问题出在这一行

new CountDownTask().cancel(true);

您正在创建一个新的CountDownTask并取消它.取消现有的Asynctask实例.

例如

private CountDownTask cT;  // declare as member

开始吧

ct = new CountDownTask();
ct.execute();

并取消喜欢

ct.cancel(true);