Android - NullPointerException：storage == null

嗨我遇到了一個Android應用程序的問題，我正在構建一個在線教程，當我嘗試運行它提到的異常時，它不斷崩潰。我真的很感謝一些關於如何阻止這個錯誤的幫助。這裏是我的主要活動：Android - NullPointerException：storage == null

package com.niall.easytxt; 

import android.app.Activity; 
import android.content.Intent; 
import android.database.DataSetObserver; 
import android.os.Bundle; 
import android.view.KeyEvent; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.View.OnKeyListener; 
import android.widget.AbsListView; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ListView; 

public class MainActivity extends Activity { 

private ChatArrayAdapter adp; 
private ListView list; 
private EditText chatText; 
private Button send; 
Intent in; 
private boolean side = false; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    Intent i = getIntent(); 
    send = (Button)findViewById(R.id.btn); 
    list = (ListView)findViewById(R.id.listview); 
    adp = new ChatArrayAdapter(getApplicationContext(),R.layout.chat, null); 
    chatText = (EditText)findViewById(R.id.chat); 
    chatText.setOnKeyListener(new OnKeyListener(){ 
     public boolean onKey(View v, int keyCode, KeyEvent event){ 
      if((event.getAction()==KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) 
      { 
       return sendChatMessage(); 
      } 


      return false; 
     } 






    }); 
    send.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View v) { 

      sendChatMessage(); 
     } 
    }); 

    list.setTranscriptMode(AbsListView.TRANSCRIPT_MODE_ALWAYS_SCROLL); 
    list.setAdapter(adp); 
    adp.registerDataSetObserver(new DataSetObserver() { 
     public void OnChanged(){ 
      super.onChanged(); 
      list.setSelection(adp.getCount() -1); 
     } 

    }); 


    } 


private boolean sendChatMessage() { 


    adp.add(new ChatMessage(side,chatText.getText().toString())); 
    chatText.setText(""); 

    side =! side; 


    return true; 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 
}

而且我ChatArrayAdapter：

package com.niall.easytxt; 

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

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.view.Gravity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.LinearLayout; 
import android.widget.TextView; 

public class ChatArrayAdapter extends ArrayAdapter<ChatMessage>{ 
private TextView chatText; 
private List<ChatMessage> MessageList = new ArrayList<ChatMessage>(); 
private LinearLayout layout; 




public ChatArrayAdapter(Context context, int resource, ChatMessage[] objects) { 
    super(context, resource, objects); 

} 

public void add(ChatMessage object) { 

    MessageList.add(object); 
    super.add(object); 
} 
public int getCount() 
{ 
    return this.MessageList.size(); 
} 
public ChatMessage getItem(int index) 
{ 

    return this.MessageList.get(index); 

} 
public View getView(int position, View ConvertView, ViewGroup parent) 
{ 
    View v = ConvertView; 
    if(v==null){ 
     LayoutInflater inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     v =inflater.inflate(R.layout.chat, parent,false); 
    } 

    layout = (LinearLayout)v.findViewById(R.id.Message1); 
    ChatMessage messageobj = getItem(position); 
    chatText = (TextView)v.findViewById(R.id.SingleMessage); 

    chatText.setText(messageobj.message); 
    chatText.setBackgroundResource(messageobj.left ? R.drawable.bubble_a :R.drawable.bubble_b); 
    layout.setGravity(messageobj.left?Gravity.START:Gravity.END); 

    return v; 

} 
public Bitmap decodeToBitmap(byte[] decodedByte){ 
    return BitmapFactory.decodeByteArray(decodedByte, 0, decodedByte.length); 
} 

}

這裏的logcat的

04-29 05:40:03.988: D/AndroidRuntime(1794): Shutting down VM 
04-29 05:40:03.988: E/AndroidRuntime(1794): FATAL EXCEPTION: main 
04-29 05:40:03.988: E/AndroidRuntime(1794): Process: com.niall.easytxt, PID: 1794 
04-29 05:40:03.988: E/AndroidRuntime(1794): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.niall.easytxt/com.niall.easytxt.MainActivity}: java.lang.NullPointerException: storage == null 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread.access$800(ActivityThread.java:144) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.os.Handler.dispatchMessage(Handler.java:102) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.os.Looper.loop(Looper.java:135) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread.main(ActivityThread.java:5221) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at java.lang.reflect.Method.invoke(Native Method) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at java.lang.reflect.Method.invoke(Method.java:372) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
04-29 05:40:03.988: E/AndroidRuntime(1794): Caused by: java.lang.NullPointerException: storage == null 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at java.util.Arrays$ArrayList.<init>(Arrays.java:38) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at java.util.Arrays.asList(Arrays.java:155) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:128) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at com.niall.easytxt.ChatArrayAdapter.<init>(ChatArrayAdapter.java:26) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at com.niall.easytxt.MainActivity.onCreate(MainActivity.java:33) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.Activity.performCreate(Activity.java:5933) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) 
04-29 05:40:03.988: E/AndroidRuntime(1794):  ... 10 more

來源

2015-04-29 Niall

發佈您的logcat – Rami

只需將其添加到那裏的問題。 – Niall

adp = new ChatArrayAdapter(getApplicationContext(),R.layout.chat, null);

你的問題就出在這條線上。您將作爲數據集傳遞null。空引用ChatMessage[]。超級構造函數調用

Arrays.asList(objects)

這是造成異常。修復它提供了一個空的數據集。例如，你可以改變你的一樣構造：在MainActivity

adp = new ChatArrayAdapter(getApplicationContext(),R.layout.chat, null);

的第三個參數是呼叫

public ChatArrayAdapter(Context context, int resource) { 
    super(context, resource, MessageList); 
}

來源

2015-04-29 09:42:33 Blackbelt

好的，謝謝，這有什麼簡單的解決辦法嗎？ – Niall

感謝它的工作 – Niall

歡迎您 – Blackbelt

中的onCreate裏面是數據集，其中適配器將提取數據。傳遞null將使它在嘗試訪問數據時立即拋出NullPointerException。

所以要解決這個問題，只需將該「null」改爲實際的ChatMessage數組。

來源

2015-04-29 09:44:26 LuigiPower

謝謝你的幫助 – Niall

Android - NullPointerException：storage == null

回答

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