Пользовательский адаптер getview throws NullPointerException, когда переменные не являются нулевыми

Question

Я пытаюсь настроить пользовательский адаптер для отображения сообщений пользователю с помощью приложения для демонстрационного чата в представлении списка, но получая ошибки в методе getView моего адаптера пользовательского списка.

• Я сделал двойную проверку на своих шагах и отладку, чтобы выяснить, является ли держатель не null. Но владелец не является нулевым, как вы можете видеть в моем отладчике переменной выводе.

Ошибка в строке:

holder.message.setText("lol"); 

Что может быть возможная ошибка в моей GetView() заказного адаптера? Спасибо за любой намек и заблаговременно.

Мой заказ адаптер:

import java.util.ArrayList; 

import android.content.Context; 
import android.support.v4.view.ViewPager.LayoutParams; 
import android.util.Log; 
import android.view.Gravity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 

public class ChattingAdapter extends BaseAdapter{ 
    private Context mContext; 
    private ArrayList<ChatMessage> mMessages; 


    public ChattingAdapter(Context context, ArrayList<ChatMessage> messages) { 
     super(); 
     this.mContext = context; 
     this.mMessages = messages; 
    } 
    @Override 
    public int getCount() { 
     return mMessages.size(); 
    } 
    @Override 
    public Object getItem(int position) {  
     return mMessages.get(position); 
    } 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     ChatMessage message = (ChatMessage) this.getItem(position); 

     ViewHolder holder; 
     if(convertView == null) 
     { 
      holder = new ViewHolder(); 
      convertView = LayoutInflater.from(mContext).inflate(R.layout.listener, parent, false); 
      holder.message = (TextView) convertView.findViewById(R.id.text1); 
      convertView.setTag(holder); 
     } 
     else 
      holder = (ViewHolder) convertView.getTag(); 
     Log.wtf("message", message.getMessage()); 
     //holder.message.setText(message.getMessage()); 
     holder.message.setText("lol"); 
     LayoutParams lp = (LayoutParams) holder.message.getLayoutParams();  

     //Check whether message is mine to show green background and align to right 

     if(message.isMine()) 

     { 
       holder.message.setBackgroundResource(R.drawable.speech_bubble_green); 
       lp.gravity = Gravity.RIGHT; 

     } 
     //If not mine then it is from sender to show orange background and align to left 

     else 

     { 

      holder.message.setBackgroundResource(R.drawable.speech_bubble_orange);   
      lp.gravity = Gravity.LEFT; 

     } 
      holder.message.setLayoutParams(lp); 
      //holder.message.setTextColor(R.color.textColor); 

     return convertView; 
    } 
    private static class ViewHolder 
    { 
     TextView message; 
    } 

    @Override 
    public long getItemId(int position) { 
     //Unimplemented, because we aren't using Sqlite. 
     return position; 
    } 

} 

Мои результаты отладки для переменных:

holder ChattingAdapter$ViewHolder (id=830019560368) 
this ChattingAdapter (id=830019493992) 
message ChatMessage (id=830019492960) 
position 0 
convertView LinearLayout (id=830019561504) 
parent ListView (id=830018556296) 

Мои Xml макеты: listitem.xml

<?xml version="1.0" encoding="utf-8"?> 
<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/text1" 
    android:background="@drawable/speech_bubble_green" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:singleLine="false" 
    android:textStyle="bold" /> 

listener.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:padding="10dip" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"> 

    <ListView 
     android:id="@android:id/list" 
     android:layout_width="wrap_content" 
     android:layout_height="0px" 
     android:layout_weight="1" 
     android:transcriptMode="normal" 
     android:stackFromBottom="true" 
     android:fadingEdge="none" android:padding="4dp" 
     android:fastScrollEnabled="true" android:smoothScrollbar="false" 
     android:focusable="true"/> 

     <LinearLayout android:layout_width="fill_parent" 
     android:layout_height="wrap_content" android:orientation="horizontal" 
     android:gravity="center_vertical" 
     android:padding="4dp"> 

     <EditText android:id="@+id/chat_input" 
      android:layout_width="0dip" 
      android:layout_height="fill_parent" 
      android:layout_weight="1" 
      android:maxLines="5" 
      android:inputType="textShortMessage|textAutoCorrect|textMultiLine|textCapSentences" 
      android:imeOptions="actionSend|flagNoExtractUi" 
      android:cursorVisible="true" 
      android:hint="Enter message" /> 

     <Button android:id="@+id/chat_send_message" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="send" /> 

     </LinearLayout> 


</LinearLayout> 

Мой трассировки стека:

02-21 16:48:36.008: E/Trace(18696): error opening trace file: No such file or directory (2) 
02-21 16:49:00.008: A/Service(18696): connected 
02-21 16:52:07.508: A/message(18696): Hello 
02-21 16:52:26.018: E/AndroidRuntime(18696): FATAL EXCEPTION: main 
02-21 16:52:26.018: E/AndroidRuntime(18696): java.lang.NullPointerException 
02-21 16:52:26.018: E/AndroidRuntime(18696): at com.example.konnect.ChattingAdapter.getView(ChattingAdapter.java:49) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.AbsListView.obtainView(AbsListView.java:2273) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.ListView.makeAndAddView(ListView.java:1769) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.ListView.fillUp(ListView.java:706) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.ListView.layoutChildren(ListView.java:1626) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.AbsListView.onLayout(AbsListView.java:2108) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.View.layout(View.java:13754) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewGroup.layout(ViewGroup.java:4364) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.onLayout(LinearLayout.java:1420) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.View.layout(View.java:13754) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewGroup.layout(ViewGroup.java:4364) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.FrameLayout.onLayout(FrameLayout.java:448) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.View.layout(View.java:13754) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewGroup.layout(ViewGroup.java:4364) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.LinearLayout.onLayout(LinearLayout.java:1420) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.View.layout(View.java:13754) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewGroup.layout(ViewGroup.java:4364) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.widget.FrameLayout.onLayout(FrameLayout.java:448) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.View.layout(View.java:13754) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewGroup.layout(ViewGroup.java:4364) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1868) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1689) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4214) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.Choreographer.doCallbacks(Choreographer.java:555) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.Choreographer.doFrame(Choreographer.java:525) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.os.Handler.handleCallback(Handler.java:615) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.os.Handler.dispatchMessage(Handler.java:92) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.os.Looper.loop(Looper.java:137) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at android.app.ActivityThread.main(ActivityThread.java:4931) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at java.lang.reflect.Method.invokeNative(Native Method) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at java.lang.reflect.Method.invoke(Method.java:511) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558) 
02-21 16:52:26.018: E/AndroidRuntime(18696): at dalvik.system.NativeStart.main(Native Method) 
02-21 16:52:31.008: E/Trace(18898): error opening trace file: No such file or directory (2) 

Функция вызова пользовательского адаптера на добавление новых сообщений:

ArrayList<ChatMessage> messagex= new ArrayList<ChatMessage>();; 
ChattingAdapter adaptex; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 

super.onCreate(savedInstanceState); 
setContentView(R.layout.listener); 
messagex.add(new ChatMessage("Hello", false)); 
adaptex = new ChattingAdapter(getApplicationContext(),messagex); 
setListAdapter(adaptex); 
Button send_button = (Button) findViewById(R.id.chat_send_message); 
sender_message = (EditText) findViewById(R.id.chat_input); 
send_button.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View v) { 
     msg = sender_message.getText().toString(); 
     if(!(msg.length()==0)){ 
      messagex.add(new ChatMessage(msg, true)); 
      //addNewMessage(new ChatMessage(msg, true)); 
      adaptex.notifyDataSetChanged(); 
      getListView().setSelection(messagex.size()-1); 
       } 
     }}); 

ChatMessage класса:

public class ChatMessage { 

    String message; 
    /** 
    * boolean to determine, who is sender of this message 
    */ 
    boolean isMine; 

    // boolean isStatusMessage; 

     /** 
     * Constructor to make a Message object 
     */ 
     public ChatMessage(String message, boolean isMine) { 
      super(); 
      this.message = message; 
      this.isMine = isMine; 
     // this.isStatusMessage = false; 
     } 
     /** 
     * Constructor to make a status Message object 
     * consider the parameters are swaped from default Message constructor, 
     * not a good approach but have to go with it. 
     */ 
     public ChatMessage(boolean status, String message) { 
      super(); 
      this.message = message; 
      this.isMine = false; 
      //this.isStatusMessage = status; 
     } 
     public String getMessage() { 
      return message; 
     } 
     public void setMessage(String message) { 
      this.message = message; 
     } 
     public boolean isMine() { 
      return isMine; 
     } 
     public void setMine(boolean isMine) { 
      this.isMine = isMine; 
     } 
     /** 
     public boolean isStatusMessage() { 
      return isStatusMessage; 
     } 
     public void setStatusMessage(boolean isStatusMessage) { 
      this.isStatusMessage = isStatusMessage; 
     } 
     */ 
} 

Answer 1

Вы

convertView = LayoutInflater.from(mContext).inflate(R.layout.listener, parent, false); 

, а затем

holder.message = (TextView) convertView.findViewById(R.id.text1); 

Но вы TextView с идентификатором text1 в listitem.xml не listener.xml который вы раздувать.

listitem.xml

<?xml version="1.0" encoding="utf-8"?> 
<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/text1" 

Следовательно, вы инициализация не удается

holder.message = (TextView) convertView.findViewById(R.id.text1); 

Следовательно NullPointerException @

holder.message.setText("lol"); 

Решение: Переход на

convertView = LayoutInflater.from(mContext).inflate(R.layout.listitem, parent, false); 

Answer 2

Изменение:

convertView = LayoutInflater.from(mContext).inflate(R.layout.listener, parent, false); 

к:

convertView = LayoutInflater.from(mContext).inflate(R.layout.listitem, parent, false);