android.content.Context.getSystemService (java.lang.String) throwing nullpointerexception

Question

Я делаю простой чат-приложение. Но когда я начала чата деятельности это метание исключение NullPointer ..

Так что это ошибка,

E/AndroidRuntime: FATAL EXCEPTION: main 
       Process: com.buckydroid.chat, PID: 1293 
       java.lang.RuntimeException: Unable to start activity ComponentInfo{com.buckydroid.chat/com.buckydroid.chat.ChatView}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6126) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference 
        at android.view.LayoutInflater.from(LayoutInflater.java:232) 
        at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:181) 
        at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:114) 
        at com.buckydroid.chat.ChatAdapter.<init>(ChatAdapter.java:0) 
        at com.buckydroid.chat.ChatView.onCreate(ChatView.java:31) 
        at android.app.Activity.performCreate(Activity.java:6679) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
        at android.app.ActivityThread.-wrap12(ActivityThread.java)  
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
        at android.os.Handler.dispatchMessage(Handler.java:102)  
        at android.os.Looper.loop(Looper.java:154)  
        at android.app.ActivityThread.main(ActivityThread.java:6126)  
        at java.lang.reflect.Method.invoke(Native Method)  
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  

А вот мой chatadapter код

private List<ChatDataProvider> chat_list= new ArrayList<ChatDataProvider>(); 
    private TextView chat_text; 
    Context ctx; 

    public ChatAdapter(Context context, int resource) { 
     super(context, resource); 
     ctx = context; 
    } 

    @Override 
    public void add(ChatDataProvider object) { 
     chat_list.add(object); 
     super.add(object); 
    } 

    @Override 
    public int getCount() { 

     return chat_list.size(); 
    } 


    @Override 
    public ChatDataProvider getItem(int position) { 
     return chat_list.get(position); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     if(convertView == null){ 
      LayoutInflater layoutInflater =(LayoutInflater) ctx.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      convertView = layoutInflater.inflate(R.layout.single_chat_message,parent,false); 
     } 
     chat_text = (TextView)convertView.findViewById(R.id.message_text); 
     String Message; 
     boolean POSITION; 
     ChatDataProvider provider = getItem(position); 
     Message=provider.message; 
     POSITION = provider.position; 
     chat_text.setText(Message); 

     chat_text.setBackgroundResource(POSITION ? R.drawable.bubble : R.drawable.bubble); 
     RelativeLayout.LayoutParams layoutParams= new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT); 

     if (!POSITION){ 
      layoutParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT); 
     }else { 
      layoutParams.addRule(RelativeLayout.ALIGN_PARENT_LEFT); 
     } 
     chat_text.setLayoutParams(layoutParams); 

     return convertView; 
    } 
} 

И я пытаюсь начать активность ChatView из основного вида деятельности.

Вот код класса chatview Java

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.chat_view); 
    chat_list = (ListView)findViewById(R.id.message_list); 
    chat_text = (EditText)findViewById(R.id.chat_input_text); 
    send_btn = (ImageButton) findViewById(R.id.send); 
    chatAdapter = new ChatAdapter(context,R.layout.single_chat_message); 
    chat_list.setAdapter(chatAdapter); 
    chat_list.setTranscriptMode(AbsListView.TRANSCRIPT_MODE_ALWAYS_SCROLL); 

    send_btn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      chatAdapter.add(new ChatDataProvider(position,chat_text.getText().toString())); 
      position = !position; 
      chat_text.setText(""); 
     } 
    }); 


} 

Answer 1

вам необходимо передать контекст деятельности в конструкторе адаптера класса

если вы используете активность

ChatAdapter chatAdapter=new ChatAdapter(this, your layout id);