ListView錯誤android

Question

我有一個方法，我用來接收一些信息。我向這個方法發送一個字符串（服務器方向）和兩個包含用戶和密碼的字符串，並且我收到一個包含所有信息的String []。然後，我使用String []值來訪問ArrayAdapter，但是我在logcat中顯示錯誤，我不知道爲什麼會出現此錯誤...在預覽版本中，我使用自己的值，但沒有「String []值」的作品完美，但現在我不知道它爲什麼不起作用。

String[] values; 

@SuppressLint("InlinedApi") 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_USER_LANDSCAPE); 
    setContentView(R.layout.activity_select_environment); 

    myBundle = getIntent().getExtras(); 

    user = myBundle.getString("user"); 
    password = myBundle.getString("password"); 

    values = request("http://myIp/XXX/post.php?request=1", user, password); 

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, android.R.id.text1, values); 
} 

另一種方法是在下：

public String[] request(String requesturl, String user, String password) 
{ 
    String result[] = new String[100]; 

    try 
    { 
     HttpClient httpclient = new DefaultHttpClient(); 

     HttpPost httppost = new HttpPost(requesturl); 

     String results = ""; 

     //Varibles POST 
     List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2); 
     nameValuePairs.add(new BasicNameValuePair("user", user)); 
     nameValuePairs.add(new BasicNameValuePair("password", password));       

     httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 

     //Execute HTTP Post Request 
     HttpResponse response = httpclient.execute(httppost); 
     response.getAllHeaders(); 
     response.getEntity(); 
     result[0] = "";                   
     if(response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) 
     { 
      results = EntityUtils.toString(response.getEntity());   
      if(!results.equals("-1")) 
      { 
       JSONObject jsonResponse = new JSONObject(results); 

       JSONArray jsonMainNode = jsonResponse.optJSONArray("edificios"); 

       int lengthJsonArr =jsonMainNode.length(); 
       for(int i = 0; i < lengthJsonArr; i++) 
       { 
        JSONObject jsonChildNode = jsonMainNode.getJSONObject(i); 
        result[i] = jsonChildNode.optString("nombre"); 
       } 
      }     
     } 

     return result; 
    } 
    catch(Exception ex) 
    { 
     result[0] = "error"; 
     return result; 
    } 
} 

以下是錯誤的logcat的。

03-31 09:02:22.920: W/dalvikvm(2016): threadid=1: thread exiting with uncaught exception (group=0xb3b0ab90) 
03-31 09:02:22.950: E/AndroidRuntime(2016): FATAL EXCEPTION: main 
03-31 09:02:22.950: E/AndroidRuntime(2016): Process: com.example.en4dis, PID: 2016 
03-31 09:02:22.950: E/AndroidRuntime(2016): java.lang.NullPointerException 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.AbsListView.obtainView(AbsListView.java:2240) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1263) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.ListView.onMeasure(ListView.java:1175) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.View.measure(View.java:16458) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.RelativeLayout.measureChild(RelativeLayout.java:689) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:473) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.View.measure(View.java:16458) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.View.measure(View.java:16458) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.View.measure(View.java:16458) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.View.measure(View.java:16458) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.Choreographer.doCallbacks(Choreographer.java:562) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.Choreographer.doFrame(Choreographer.java:532) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.os.Handler.handleCallback(Handler.java:733) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.os.Handler.dispatchMessage(Handler.java:95) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.os.Looper.loop(Looper.java:137) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at android.app.ActivityThread.main(ActivityThread.java:4998) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at java.lang.reflect.Method.invoke(Method.java:515) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593) 
03-31 09:02:22.950: E/AndroidRuntime(2016):  at dalvik.system.NativeStart.main(Native Method) 

Answer 1

我覺得你的問題是在這裏：

String result[] = new String[100]; 

您初始化與100的長度數組現在你只填寫您的陣列的一部分。這意味着在你的記憶，你將有這樣的事情

Index:  0  1   98  99 
Values: Value1 | Value2| ... | null | null 

（編輯：我知道這並不完全準確，因爲只有存儲的引用，但它更容易理解這樣）

現在當你將它傳遞給你的ArrayAdapter時，它會解析每個元素，最後它會嘗試以null作爲String來佈局TextView。顯然Android不喜歡那樣。

你所要做的就是獲得一個完全符合你數值長度的數組。我建議先使用列表並稍後創建一個數組。例如（未經測試的僞代碼）

public String[] request(String requesturl, String user, String password){ 

    //init List 
    List<String> values = new ArrayList<String>(); 

    //add values to List like this 
    values.add("myString"); 


    //return a array with the correct size at last 
    return values.toArray(new String[values.size()]); 

} 

請確保對您的錯誤情況也做同樣的事情。