在按钮单击中执行AsyncTask而不会出现崩溃或异常

Question

我看到很多这些问题的遗嘱(这里,这里,这里和这里),但我没有得到解决我的问题.

这是我的应用程序的想法

从URL中获取内容并在每次单击按钮时使用textview显示它.

(URL内容将为每次刷新随机生成不同的文本)

---

这是我的应用程序的旧代码完美地工作但StackOverflow人员建议我使用AsyncTask

我在doInBackground()方法中指定了获取URL内容操作,并在onCreate的 Button Click Event中调用了new myAsyncTask.execute().

它只适用于第一次点击,然后我的应用程序崩溃了.它说AsyncTask应该只调用一次.但我希望我的TextView在每个按钮点击事件上更新.

---

那么,我现在应该怎么做

我是否要取消之前的AsyncTask并调用新的(或)我想为AsyncTask初始化新对象并再次调用它(这是最糟糕的方法)

如何使用AsyncTask或任何Alternate在我的应用程序中实现我的想法？

这是我的代码:

public class MainActivity extends AppCompatActivity {

    TextView resultView;String TAG="MainActivity kbt";
    SmoothProgressBar mProgressBar;
    Context context;
    MyAsyncTask myAsyncTask;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
      //  StrictMode.enableDefaults();  //Used to executes URL connection on MainThread without getting Exception
        setContentView(R.layout.activity_main);
        mProgressBar = (SmoothProgressBar) findViewById(R.id.progressBar);
       StrictMode.enableDefaults();
        resultView = (TextView) findViewById(R.id.result);
        myAsyncTask=new MyAsyncTask();
       // mProgressBar.setVisibility(SmoothProgressBar.INVISIBLE);


        Button insert=(Button) findViewById(R.id.button);
        insert.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                // TODO Auto-generated method stub
                myAsyncTask.execute();

            }
        });
    }   

    private class MyAsyncTask extends AsyncTask<Void, Void, Void> {
        String mTAG = "myAsyncTask";

        @Override
        protected void onPreExecute() {
           mProgressBar.progressiveStart();
        }

        @Override
        protected Void doInBackground(Void... arg) {

            try {
                getData();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }


        @Override
        protected void onPostExecute(Void a) {
            mProgressBar.progressiveStop();
        }
    }

 public void getData() throws IOException {

        String result = "";
        InputStream isr = null;  

        URLConnection urlConnection = null;
        URL url = new URL("http://kbtganesh.16mb.com/index.php");
        Log.d(TAG,"After  URL NOT WORKING");   //AFTER THIS.... NEXT LOG (ie GOT URL CONNETION) IS NOT PRINTED

        urlConnection =  url.openConnection();

        Log.d(TAG, "GOT URL CONNETION");

        Log.d(TAG, "GOT URL CONNECTED");
        isr =urlConnection.getInputStream();
        Log.d(TAG,"AFTER ISR EQ");



        //convert response to string

        try {
           // BufferedReader reader = new BufferedReader(new InputStreamReader(isr,"iso-8859-1"),8);
            BufferedReader reader = new BufferedReader(new InputStreamReader(isr));
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            isr.close();

            result=sb.toString();
        }
        catch(Exception e){
            Log.e("log_tag", "Error converting result "+e.toString());
        }

        //parse json data
        try {
            resultView.setText(result);
        }
        catch(Exception e) {
            Log.e("log_tag", "Couldn't set text, damnit.");
        }

    }

}

提前致谢... (:

Answer 1

最后,我在StackOverflow朋友的帮助下解决了我的问题.

移动myAsyncTask=new MyAsyncTask();内部onClick()方法解决了我的问题.这是多次执行AsyncTask的最佳方法.

AsyncTask实例在执行完后最终将被垃圾收集.因此我们不需要担心创建多个实例.它们将自动进入.

MyAsyncTask myAsyncTask;
insert.setOnClickListener(new View.OnClickListener() {

        @Override 
        public void onClick(View view) {
            // TODO Auto-generated method stub 
            myAsyncTask=new MyAsyncTask();
            // TODO Auto-generated method stub
           myAsyncTask.execute();


        } 
    });