延伸导致程序崩溃的应用程序示例如何？

-1

public class MainActivity extends ActionBarActivity implements OnCheckedChangeListener{ 
    TextView txv=(TextView)findViewById(R.id.textView1); 
    Spinner spinner1=(Spinner)findViewById(R.id.spinner1); 
    RadioGroup rdg=(RadioGroup)findViewById(R.id.radioGroup1); 
    String msg=""; 
    String[] way1={"商務車廂","經濟車廂","自由座"}; 
    String[] way2={"商務艙","頭等艙","經濟艙"}; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     rdg.setOnCheckedChangeListener(this); 
    } 

    @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); 
    } 

    @Override 
    public void onCheckedChanged(RadioGroup radio0, int radio1) { 
     // TODO Auto-generated method stub  
     if (radio0.getCheckedRadioButtonId()==R.id.radio0){ 
      msg="高鐵"; 
      ArrayAdapter<String> tempAd =new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,way1); 
      tempAd.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
      spinner1.setAdapter(tempAd); 
     } 
     else{ 
      msg="飛機"; 
      ArrayAdapter<String> tempAd =new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,way2); 
      tempAd.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
      spinner1.setAdapter(tempAd); 
     } 
    } 

    public void buy(View v){ 
     msg=(msg+"-"+spinner1.getSelectedItem()); 
     txv.setText("XXX您好，您訂購的項目為:"+msg); 
    }

这里是logcat的消息：

10-17 17:48:47.224: E/AndroidRuntime(720): FATAL EXCEPTION: main 
10-17 17:48:47.224: E/AndroidRuntime(720): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.asd/com.example.asd.MainActivity}: java.lang.NullPointerException 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.os.Handler.dispatchMessage(Handler.java:99) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.os.Looper.loop(Looper.java:137) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread.main(ActivityThread.java:5041) 
10-17 17:48:47.224: E/AndroidRuntime(720): at java.lang.reflect.Method.invokeNative(Native Method) 
10-17 17:48:47.224: E/AndroidRuntime(720): at java.lang.reflect.Method.invoke(Method.java:511) 
10-17 17:48:47.224: E/AndroidRuntime(720): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
10-17 17:48:47.224: E/AndroidRuntime(720): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
10-17 17:48:47.224: E/AndroidRuntime(720): at dalvik.system.NativeStart.main(Native Method) 
10-17 17:48:47.224: E/AndroidRuntime(720): Caused by: java.lang.NullPointerException 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.Activity.findViewById(Activity.java:1839) 
10-17 17:48:47.224: E/AndroidRuntime(720): at com.example.asd.MainActivity.<init>(MainActivity.java:17) 
10-17 17:48:47.224: E/AndroidRuntime(720): at java.lang.Class.newInstanceImpl(Native Method) 
10-17 17:48:47.224: E/AndroidRuntime(720): at java.lang.Class.newInstance(Class.java:1319) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.Instrumentation.newActivity(Instrumentation.java:1054) 
10-17 17:48:47.224: E/AndroidRuntime(720): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097) 
10-17 17:48:47.224: E/AndroidRuntime(720): ... 11 more

来源

2014-10-17 Paul Chang

您是否更新了清单文件以显示您使用自定义应用程序？ – j2emanue 2014-10-17 18:12:13

恳请更多解释问题！你的问题中只有代码！ – 2014-10-17 18:13:01

我的英语不是很好。这就是我所知道的。当我使用AVD。它向我显示一条消息“不幸的是，asd已经停止” – 2014-10-17 18:28:51

嗯，这是在构造函数中抛出一个NullPointerException。

你不应该在那里做findViewById。你应该在onCreate()之后，你叫setContentView()。

来源

2014-10-17 21:57:32

延伸导致程序崩溃的应用程序示例如何？

回答

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