java - Android后台任务-如何访问返回值

Question

当后台任务返回一个值时，如何从另一个类访问它。只是使用它作为示例代码，但我想要的是后台任务执行某些操作并返回一个值。

protected String doInBackground(String... params) {
    publishProgress("Sleeping..."); // Calls onProgressUpdate()
    try {
       // Do your long operations here and return the result
       int time = Integer.parseInt(params[0]);    

       // Sleeping for given time period
       Thread.sleep(time);
       resp = "Slept for " + time + " milliseconds";
   } catch (InterruptedException e) {
       e.printStackTrace();
       resp = e.getMessage();
   } catch (Exception e) {
       e.printStackTrace();
       resp = e.getMessage();
   }

   **return resp;**
}

Answer 1

为此，您需要扩展 asynktask 类，例如

extends AsyncTask<String, String, String>

@Override
protected void onPostExecute(String result) {
    //heare result is value you return from doInBackground() method 
    //this is work on UI thread
} 

类看起来像

public class AsyncTaskGetResult extends AsyncTask<String, String, String> {

    PrintListner mPrintListner ;      
    private AsyncTaskGetResult (PrintListner mPrintListner) {
        this.mPrintListner = mPrintListner;

    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

    }
    @Override
    protected String doInBackground(String... params) {
        return result;
    }

    @Override
    protected void onPostExecute(String result) {
    //heare result is value you return from doInBackground() method 
    //this is work on UI thread
    this.mPrintListner.getResult(result);
   }

}

public interface PrintListner {
    public void getResult(String receiptItem);
}

如果您需要在另一个类中访问它，您可以为此编写监听器并在您的 Activity 中实现

public class MyActivity extends Activity implements PrintListner{

       @Override
       public void getResult(String receiptItem){
        //Do whatever you want
       }
    }   

并像 new AsyncTaskGetResult(this).execute(yourString); 那样调用它