Android：如何使循环在AsyncTask完成后继续循环（onPostExecute）

Question

我有一个大于1的值，所以我计划为每个值执行一个for循环。 问题是for循环正在循环/继续，即使AsyncTask尚未完成。

AsyncTask类

public class Server extends AsyncTask<JSONObject, Void, Void> {

   @Override
   protected Void doInBackground(JSONObject... params) {
       .........
   }

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

活动

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_a);

    for(int i=0; i<10; i++){
       Server  myServer = new Server();
       myServer.execute(i);
    }
}

Answer 1

正如@ cricket_007所评论的那样，循环不会等待，因为AsyncTask是异步的，因此循环继续进行而无需等待AsyncTask完成。 因此，据我所知，您需要执行以下操作。

您需要定义一个这样的接口。

public interface ResponseListener {
    void responseReceiver();
}

现在像这样修改您的AsyncTask

public class Server extends AsyncTask<JSONObject, Void, Void> {

   public ResponseListener responseListener;

   @Override
   protected Void doInBackground(JSONObject... params) {
       // .........
   }

   @Override
   protected void onPostExecute(Void result) {
       // ......... Other code
       // Now here's the callback function to the main activity.
       responseListener.responseReceiver(); 
   }
}

现在，从您的活动中，您需要执行以下操作。

public class YourActivity extends Activity implements HttpResponseListener {
    public int count = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_a);

        Server  myServer = new Server();
        myServer.responseListener = this;
        myServer.execute(i);
    }

    // Callback method implementation
    @Override
    public void responseReceiver() {
        // This is the callback function and it gets called when one AsyncTask finishes.
        // Increase the count here and keep track of how many times the AsyncTask has been executed.

        // Do something 
        count++; 

        // Now call the next AsyncTask again if the count haven't reach 10 already
        if(count <= 10) {
            Server  myServer = new Server();
            myServer.responseListener = this;
            myServer.execute(i);
        }
    }
}

希望能有所帮助。

Answer 2

我的解决方案有点远，但我想做的工作。

static Boolean ASYNC_TASK_FINISHED;    
for(int i=0; i<10; i++){
    ASYNC_TASK_FINISHED = false;
    Server  myServer = new Server();
    myServer.execute(i);

    while(!ASYNC_TASK_FINISHED){ }
}

然后在您的AsyncTask

@Override
protected void onPostExecute(Void result) {
   ...

   ASYNC_TASK_FINISHED = true;
}

您应该将ASYNC_TASK_FINISHED变量设置为可通过Activity和AsyncTask访问的全局单例。