錯誤：「必須從UI線程調用方法getText（），當前推斷的線程是worker。」

Question

在項目上工作時，我在以下活動中遇到錯誤。 1. Login.java 關於以下代碼行。

Line：「String username = user.getText（）。toString（）;」 錯誤：「必須從UI線程調用方法getText（），當前推斷的線程是worker。」

這是我的整個活動代碼。

package com.example.mysqltest; 

import java.util.ArrayList; 
import java.util.List; 

import org.apache.http.NameValuePair; 
import org.apache.http.message.BasicNameValuePair; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.app.Activity; 
import android.app.ProgressDialog; 
import android.content.Intent; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 

public class Login extends Activity implements OnClickListener { 

    private EditText user, pass; 
    private Button mSubmit, mRegister; 

    // Progress Dialog 
    private ProgressDialog pDialog; 

    // JSON parser class 
    JSONParser jsonParser = new JSONParser(); 

    //php login script location: 

    //localhost : 
    //testing on your device 
    //put your local ip instead, on windows, run CMD > ipconfig 
    //or in mac's terminal type ifconfig and look for the ip under en0 or en1 
    // private static final String LOGIN_URL = "http://xxx.xxx.x.x:1234/webservice/login.php"; 



    //testing from a real server: 
    //private static final String LOGIN_URL = "http://www.example.com/webservice/login.php"; 

    //JSON element ids from repsonse of php script: 
    private static final String TAG_SUCCESS = "success"; 
    private static final String TAG_MESSAGE = "message"; 

    public static String username; 
    public static String password; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.login); 

     //setup input fields 
     user = (EditText) findViewById(R.id.username); 
     pass = (EditText) findViewById(R.id.password); 

     //setup buttons 
     mSubmit = (Button) findViewById(R.id.login); 
     mRegister = (Button) findViewById(R.id.register); 

     //register listeners 
     mSubmit.setOnClickListener(this); 
     mRegister.setOnClickListener(this); 


    } 

    @Override 
    public void onClick(View v) { 
     // TODO Auto-generated method stub 
     switch (v.getId()) { 
      case R.id.login: 
       username = user.getText().toString(); 
       password = pass.getText().toString(); 
       new AttemptLogin().execute(); 
       break; 
      case R.id.register: 
       Intent i = new Intent(this, Register.class); 
       startActivity(i); 
       break; 

      default: 
       break; 
     } 
    } 

    class AttemptLogin extends AsyncTask<String, String, String> { 

     /** 
     * Before starting background thread Show Progress Dialog 
     */ 
     boolean failure = false; 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(Login.this); 
      pDialog.setMessage("Attempting login..."); 
      pDialog.setIndeterminate(false); 
      pDialog.setCancelable(true); 
      pDialog.show(); 
     } 

     @Override 
     protected String doInBackground(String... args) { 
      // TODO Auto-generated method stub 
      // Check for success tag 
      int success; 

      try { 
       // Building Parameters 
       List<NameValuePair> params = new ArrayList<NameValuePair>(); 
       params.add(new BasicNameValuePair("username", username)); 
       params.add(new BasicNameValuePair("password", password)); 

       Log.d("request!", "starting"); 
       // getting product details by making HTTP request 
       JSONObject json = jsonParser.makeHttpRequest(
         LOGIN_URL, "POST", params); 

       // check your log for json response 
       Log.d("Login attempt", json.toString()); 

       // json success tag 
       success = json.getInt(TAG_SUCCESS); 
       if (success == 1) { 
        Log.d("Login Successful!", json.toString()); 
        Intent i = new Intent(Login.this, ReadComments.class); 
        finish(); 
        startActivity(i); 
        return json.getString(TAG_MESSAGE); 
       } else { 
        Log.d("Login Failure!", json.getString(TAG_MESSAGE)); 
        return json.getString(TAG_MESSAGE); 

       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return null; 

     } 

     /** 
     * After completing background task Dismiss the progress dialog 
     **/ 
     protected void onPostExecute(String file_url) { 
      // dismiss the dialog once product deleted 
      pDialog.dismiss(); 
      if (file_url != null) { 
       Toast.makeText(Login.this, file_url, Toast.LENGTH_LONG).show(); 
      } 

     } 

    } 

} 

Answer 1

除非有什麼改變，我不知道，這應該不成問題。用戶界面元素不能從後臺更新，但訪問他們的獲取者從來都不是問題。

無論如何，你可以通過向你的AsyncTask添加一個構造函數來解決這個問題，這需要兩個字符串，然後在創建任務時發送它們。

private class Login extends AsyncTask<String, String, String>{ 

// member variables of the task class 
String uName, pwd 
public AttemptLogin(String userName, String password) { 
    uName = userName; 
    pwd = password; 
} 

@Override 
protected String doInBackground(String... args) {...} 

，並通過他們在你的onClick（）

case R.id.login: 
// execute method invokes doInBackground() where we open a Http URL connection using the given Servlet URL 
//and get output response from InputStream and return it. 

// pass them here 

    new AttemptLogin(uname.getText().toString(), password.getText().toString()).execute(); 
       break;