求大神帮忙看下 handler 出错 ,看不懂出错信息 是不是空指针
我在学习安卓开发
今天做到 handler 出错了

07-19 13:34:12.977: E/AndroidRuntime(406): FATAL EXCEPTION: main
07-19 13:34:12.977: E/AndroidRuntime(406): java.lang.NullPointerException
07-19 13:34:12.977: E/AndroidRuntime(406): at com.handlertest.HandlerTest$StartButtonListener.onClick(HandlerTest.java:37)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.view.View.performClick(View.java:2408)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.view.View$PerformClick.run(View.java:8816)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.os.Handler.handleCallback(Handler.java:587)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.os.Handler.dispatchMessage(Handler.java:92)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.os.Looper.loop(Looper.java:123)
07-19 13:34:12.977: E/AndroidRuntime(406): at android.app.ActivityThread.main(ActivityThread.java:4627)
07-19 13:34:12.977: E/AndroidRuntime(406): at java.lang.reflect.Method.invokeNative(Native Method)
07-19 13:34:12.977: E/AndroidRuntime(406): at java.lang.reflect.Method.invoke(Method.java:521)
07-19 13:34:12.977: E/AndroidRuntime(406): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-19 13:34:12.977: E/AndroidRuntime(406): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-19 13:34:12.977: E/AndroidRuntime(406): at dalvik.system.NativeStart.main(Native Method)

这是代码

// 声明变量
private Button startButton;
private Button endButton;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// 获取控件对象
startButton = (Button) findViewById(R.id.startButton);
endButton = (Button) findViewById(R.id.endButton);
// 设置监听
startButton.setOnClickListener(new StartButtonListener());
endButton.setOnClickListener(new EndButtonListener());
}

// 创建 handler对象
private Handler handler;
// 将要执行的操作写进线程对象(updateThread)的Run方法中去
Runnable updateThread = new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub
System.out.println("updateThraed");
// 在Run方法内部执行postDelayed方法或者post方法进行循环
handler.postDelayed(updateThread, 3000);
// handler.post(updateThread); 
 
}
};

// startButton的监听
class StartButtonListener implements OnClickListener {

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
// 调用handler的post方法，将线程加入到消息队列中去
System.out.println("---start thread---");
handler.post(updateThread);
}

}

// endButton的监听
class EndButtonListener implements OnClickListener {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
// 将线程移出消息队列
handler.removeCallbacks(updateThread);
}

}

楼主只声明了handler，没有实现它。
[解决办法]
handler = new Handler();
问题就解决了