崩溃与ArrayAdapter或ListView

Question

即时通讯测试与ArrayAdapyer和ListView， 当我运行此代码我的应用程序崩溃。日志什么都没说，也没有发现错误。 这里是类：

和类：

import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 

import java.util.ArrayList; 

public class MainActivity extends AppCompatActivity { 

    ListView list; 
    ArrayAdapter<String> adap; 
    ArrayList<String> arr; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     list = (ListView) findViewById(R.id.list); 
     arr = new ArrayList<String>(); 
     arr.add("hello"); 
     arr.add("name is dragon"); 
     adap = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arr); 
     list.setAdapter(adap); 


    } 

} 

LOG：

          java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.faivel.myapplication/com.example.faivel.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984) 
               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) 
               at android.app.ActivityThread.-wrap14(ActivityThread.java) 
               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) 
               at android.os.Handler.dispatchMessage(Handler.java:102) 
               at android.os.Looper.loop(Looper.java:154) 
               at android.app.ActivityThread.main(ActivityThread.java:6776) 
               at java.lang.reflect.Method.invoke(Native Method) 
               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520) 
               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410) 
              Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
               at com.example.faivel.myapplication.MainActivity.onCreate(MainActivity.java:26) 
               at android.app.Activity.performCreate(Activity.java:6955) 
               at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126) 
               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927) 
               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)  
               at android.app.ActivityThread.-wrap14(ActivityThread.java)  
               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)  
               at android.os.Handler.dispatchMessage(Handler.java:102)  
               at android.os.Looper.loop(Looper.java:154)  
               at android.app.ActivityThread.main(ActivityThread.java:6776)  
               at java.lang.reflect.Method.invoke(Native Method)  
               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)  
               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)  

这里有什么问题吗？谢谢！ 编辑：添加日志！

Answer 1

我测试你的class

package com.example.nniroula.test; 

import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 

import java.util.ArrayList; 

public class Test extends AppCompatActivity { 

    ListView list; 
    ArrayAdapter<String> adap; 
    ArrayList<String> arr; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_text); 
     list = (ListView) findViewById(R.id.list); 
     arr = new ArrayList<String>(); 
     arr.add("hello"); 
     arr.add("name is dragon"); 
     adap = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arr); 
     list.setAdapter(adap); 


    } 

} 

和xml文件

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

    <ListView 
     android:id="@+id/list" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"/> 

</LinearLayout> 

这一切工作正常。