NullPointerException в коде Android во активность OnCreate()

Question

Ниже мой Android код:

package com.example.to_dolsit; 

import java.util.ArrayList; 

import android.app.Activity; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.KeyEvent; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnKeyListener; 
import android.widget.ArrayAdapter; 
import android.widget.EditText; 
import android.widget.ListView; 

public class MainActivity extends Activity { 
    int KeyCode; 
    ListView myListView = (ListView) findViewById(R.id.listView1); 
    final EditText myEditText = (EditText) findViewById(R.id.editText1); 
    String tag = "Events"; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     //setContentView(R.layout.activity_main); 
     Log.d(tag,"ohkkkkkkkkkkkkkkkkkkkkkkkkkkkkk......................."); 
     // create the list of to do items 
     final ArrayList<String> todoItems = new ArrayList<String>(); 
     // craeate the array adapter to bind the aray to the list 
     final ArrayAdapter<String> aa; 
     aa = new ArrayAdapter<String>(this, 
       android.R.layout.simple_list_item_1, todoItems); 
     myListView.setAdapter(aa); 

     myEditText.setOnKeyListener(new OnKeyListener() { 

      @Override 
      public boolean onKey(View v, int keyCode, KeyEvent event) { 
       // TODO Auto-generated method stub 
       if (event.getAction() == KeyEvent.ACTION_DOWN) 
        if (KeyCode == KeyEvent.KEYCODE_DPAD_CENTER) { 

         todoItems.add(0, myEditText.getText().toString()); 
         aa.notifyDataSetChanged(); 
         myEditText.setText(""); 
         return true; 
        } 

       return false; 
      } 
     }); 

    } 

    @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; 
    } 


} 

Компоновка Кодекс: -

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context=".MainActivity" > 

    <EditText 
     android:id="@+id/editText1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:inputType="text" 
     android:drawableLeft="@drawable/ic_launcher" 

     android:text="@string/EditText" > 

    </EditText> 

    <ListView 
     android:id="@+id/listView1" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/editText1" 
     android:layout_below="@+id/editText1" 
     android:layout_marginLeft="15dp" 
     android:layout_marginTop="54dp" > 
    </ListView> 



</RelativeLayout> 

Это дает мне следующее сообщение об ошибке:

---

02-14 01:31:31.601: E/AndroidRuntime(10689): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.to_dolsit/com.example.to_dolsit.MainActivity}: java.lang.NullPointerException 
02-14 01:31:31.601: E/AndroidRuntime(10689): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1573) 
02-14 01:31:31.601: E/AndroidRuntime(10689): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667) 

Answer 1

Ваш ListView, скорее всего, вызывает nullpointer. Не звоните findViewById() перед вызовом setContentView(). Измените свой код на следующее.