的Android AutoCompleteTextview的OnClick

Question

public class getLocationName extends Activity { 

AutoCompleteTextView atvPlaces; 
PlacesTask placesTask; 
ParserTask parserTask; 

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

    atvPlaces = (AutoCompleteTextView) findViewById(R.id.atv_places); 
    atvPlaces.setThreshold(1);  
    atvPlaces.setOnItemClickListener(new OnItemClickListener() { 

     @Override 
     public void onItemClick(AdapterView<?> parent, View view,int position, long id) 
     { 
      AutoCompleteTextView a=(AutoCompleteTextView)view.findViewById(R.id.atv_places); 
      Log.d("TAG", a.getText().toString()); 
      Intent i=new Intent(getApplicationContext(),Dashboard.class); 
      i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 

      getApplicationContext().startActivity(i); 
     } 

    }); 
    atvPlaces.setOnTouchListener(new OnTouchListener() { 

     @Override 
     public boolean onTouch(View v, MotionEvent event) { 
       atvPlaces.showDropDown(); 
      return false; 
     } 
    }); 
    atvPlaces.addTextChangedListener(new TextWatcher() { 

     @Override 
     public void onTextChanged(CharSequence s, int start, int before, int count) { 
      placesTask = new PlacesTask();    
      placesTask.execute(s.toString()); 
     } 

     @Override 
     public void beforeTextChanged(CharSequence s, int start, int count, 
       int after) { 
      // TODO Auto-generated method stub 
     } 

     @Override 
     public void afterTextChanged(Editable s) { 
      // TODO Auto-generated method stub    
     } 
    }); 
} 

/** A method to download json data from url */ 
private String downloadUrl(String strUrl) throws IOException{ 
    String data = ""; 
    InputStream iStream = null; 
    HttpURLConnection urlConnection = null; 
    try{ 
      URL url = new URL(strUrl);     

      // Creating an http connection to communicate with url 
      urlConnection = (HttpURLConnection) url.openConnection(); 

      // Connecting to url 
      urlConnection.connect(); 

      // Reading data from url 
      iStream = urlConnection.getInputStream(); 

      BufferedReader br = new BufferedReader(new InputStreamReader(iStream)); 

      StringBuffer sb = new StringBuffer(); 

      String line = ""; 
      while((line = br.readLine()) != null){ 
        sb.append(line); 
      } 

      data = sb.toString(); 

      br.close(); 

    }catch(Exception e){ 
      Log.d("Exception while downloading url", e.toString()); 
    }finally{ 
      iStream.close(); 
      urlConnection.disconnect(); 
    } 
    return data; 
} 

// Fetches all places from GooglePlaces AutoComplete Web Service 
private class PlacesTask extends AsyncTask<String, Void, String>{ 

    @Override 
    protected String doInBackground(String... place) { 
     // For storing data from web service 
     String data = ""; 

     // Obtain browser key from https://code.google.com/apis/console 
     String key = "key=sdhdjsdsddsldsdjs"; 

     String input=""; 

     try { 
      input = "input=" + URLEncoder.encode(place[0], "utf-8"); 
     } catch (UnsupportedEncodingException e1) { 
      e1.printStackTrace(); 
     }  


     // place type to be searched 
     String types = "types=geocode"; 

     // Sensor enabled 
     String sensor = "sensor=false";   

     // Building the parameters to the web service 
     String parameters = input+"&"+types+"&"+sensor+"&"+key; 

     // Output format 
     String output = "json"; 

     // Building the url to the web service 
     String url = "https://maps.googleapis.com/maps/api/place/autocomplete/"+output+"?"+parameters; 

     try{ 
      // Fetching the data from web service in background 
      data = downloadUrl(url); 
     }catch(Exception e){ 
      Log.d("Background Task",e.toString()); 
     } 
     return data;   
    } 

    @Override 
    protected void onPostExecute(String result) {   
     super.onPostExecute(result); 

     // Creating ParserTask 
     parserTask = new ParserTask(); 

     // Starting Parsing the JSON string returned by Web Service 
     parserTask.execute(result); 
    }  
} 


/** A class to parse the Google Places in JSON format */ 
private class ParserTask extends AsyncTask<String, Integer, List<HashMap<String,String>>>{ 

    JSONObject jObject; 

    @Override 
    protected List<HashMap<String, String>> doInBackground(String... jsonData) {    

     List<HashMap<String, String>> places = null; 

     PlaceJSONParser placeJsonParser = new PlaceJSONParser(); 

     try{ 
      jObject = new JSONObject(jsonData[0]); 

      // Getting the parsed data as a List construct 
      places = placeJsonParser.parse(jObject); 


     }catch(Exception e){ 
      Log.d("Exception",e.toString()); 
     } 
     return places; 
    } 

    @Override 
    protected void onPostExecute(List<HashMap<String, String>> result) { 


      String[] from = new String[] { "description"}; 
      int[] to = new int[] { android.R.id.text1 }; 

      // Creating a SimpleAdapter for the AutoCompleteTextView    
      SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), result, android.R.layout.simple_list_item_1, from, to);    

      // Setting the adapter 
      atvPlaces.setAdapter(adapter); 


    }   
}  


} 

的logcat：

04-02 08:17:23.151: E/AndroidRuntime(3569): FATAL EXCEPTION: main 
04-02 08:17:23.151: E/AndroidRuntime(3569): Process: com.example.remindme, PID: 3569 
04-02 08:17:23.151: E/AndroidRuntime(3569): java.lang.NullPointerException 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at com.example.remindme.getLocationName$1.onItemClick(getLocationName.java:53) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AutoCompleteTextView.performCompletion(AutoCompleteTextView.java:902) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AutoCompleteTextView.access$500(AutoCompleteTextView.java:91) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AutoCompleteTextView$DropDownItemClickListener.onItemClick(AutoCompleteTextView.java:1192) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AdapterView.performItemClick(AdapterView.java:299) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AbsListView.performItemClick(AbsListView.java:1113) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:2904) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.widget.AbsListView$3.run(AbsListView.java:3638) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.os.Handler.handleCallback(Handler.java:733) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.os.Handler.dispatchMessage(Handler.java:95) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.os.Looper.loop(Looper.java:136) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at android.app.ActivityThread.main(ActivityThread.java:5017) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at java.lang.reflect.Method.invoke(Method.java:515) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
04-02 08:17:23.151: E/AndroidRuntime(3569):  at dalvik.system.NativeStart.main(Native Method) 

On Click事件我想點擊的項目，但它顯示錯誤

Answer 1

無需調用findViewById()在OnItemClickListener爲atvPlaces。

由於findViewById()沒有找到它返回null的觀點，你會得到一個NullPointerException當您嘗試訪問對象（即當你調用a.getText()法）

你已經在爲AutoCompleteTextView參考你的atvPlaces變量。因此，有沒有必要重新定義一個

以下修復了這個代碼（尤其是在每個項目上點擊！）：

atvPlaces.setOnItemClickListener(new OnItemClickListener() { 

     @Override 
     public void onItemClick(AdapterView<?> parent, View view,int position, long id) 
     { 

      Log.d("TAG", atvPlaces.getText().toString()); 
      Intent i=new Intent(getApplicationContext(),Dashboard.class); 
      i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 

      getApplicationContext().startActivity(i); 
     } 

    });