Android：執行doInBackground，setText的TextView

Question

我是android和套接字編程的新手。我正在開發一個客戶端向服務器發送字符串的項目。當服務器獲取字符串時，會更改TextView的文本。 問題是，無論何時客戶端發送字符串服務器粉碎（當我使用setText（）函數）。 這裏是我的代碼：

public class Download extends AppCompatActivity { 


GetRequestedURLAsyncTask __getRequestedURLAsyncTask; 

TextView incomingURL; 
Button downloadButton; 


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

    incomingURL = (TextView) this.findViewById(R.id.incomingURL); 
    downloadButton = (Button) this.findViewById(R.id.disconnectButton); 


    __getRequestedURLAsyncTask = new GetRequestedURLAsyncTask(this); 
    __getRequestedURLAsyncTask.execute(this); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.menu_download, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 

    //noinspection SimplifiableIfStatement 
    if (id == R.id.action_settings) { 
     return true; 
    } 

    return super.onOptionsItemSelected(item); 
} 

private class GetRequestedURLAsyncTask extends AsyncTask { 

    private Context context; 
    private TextView statusText; 

    private String requestedURL; 

    public GetRequestedURLAsyncTask(Context context) { 
     this.context = context; 
    } 

    @Override 
    protected Object doInBackground(Object[] params) { 

     ServerSocket serverSocket = null; 
     Socket client = null; 

     try { 
      Log.v("transferService", "Creating server socket"); 
      serverSocket = new ServerSocket(8282); 

      Log.v("transferService", "Creating client socket"); 
      client = serverSocket.accept(); 


      InetAddress inetAddress = client.getInetAddress(); 
      Log.d("New connection made from ", inetAddress.getHostAddress()); 

      Log.d("IncomingText", "Init input"); 

      DataInputStream input = new DataInputStream(client.getInputStream()); 



      while(true) 
      { 
       try 
       { 

        requestedURL = input.readLine().toString(); 
        Log.d("incomingText", requestedURL); 
        setRequestedUrl(requestedURL); 
       } 
       catch (IOException e) 
       { 

       } 
      } 





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

    } 


    protected void onPostExecute(String result) 
    { 

     if (result != null) 
     { 
      setRequestedUrl(result); 
     } 
    } 

    public String getRequestedUrl() 
    { 
     return this.requestedURL; 
    } 

} 

private void setRequestedUrl(String s) 
{ 
    this.incomingURL.setText(s); 
} 

}

和logcat的：

FATAL EXCEPTION: AsyncTask #1 
java.lang.RuntimeException: An error occured while executing doInBackground() 
     at android.os.AsyncTask$3.done(AsyncTask.java:299) 
     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 
     at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 
     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 
     at java.util.concurrent.FutureTask.run(FutureTask.java:137) 
     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076) 
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569) 
     at java.lang.Thread.run(Thread.java:856) 
Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. 
     at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4876) 
     at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:948) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:292) 
     at android.view.View.requestLayout(View.java:15245) 
     at android.widget.TextView.checkForRelayout(TextView.java:6632) 
     at android.widget.TextView.setText(TextView.java:3736) 
     at android.widget.TextView.setText(TextView.java:3594) 
     at android.widget.TextView.setText(TextView.java:3569) 
     at Download.setRequestedUrl(Download.java:147) 
     at Download.access$000(Download.java:24) 
     at Download$GetRequestedURLAsyncTask.doInBackground(Download.java:109) 
     at android.os.AsyncTask$2.call(AsyncTask.java:287) 
     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 

任何意見將是有益的。

Answer 1

取消方法中對setRequestedUrl(requestedURL)的呼叫。 doInBackground方法發生在主線程之外。您只能在onPreExecute，onPostExecute或onProgressUpdate方法中修改您的視圖AsyncTask