本人刚开始学习android，跟着书写了个程序，这个程序是会有一个东西随着手指拖动而移动，编译完没有问题，但是在手机上运行的时候却是意外停止，错误显示在了MainActivity的第27行，我真不知道哪里错，代码和书上写的一模一样，求大神指导
MainActivity的代码：
package com.example.test34;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.FrameLayout;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FrameLayout frameLayout=(FrameLayout)findViewById(R.id.mylayout);
final RabbitView rabbit=new RabbitView(MainActivity.this);
rabbit.setOnTouchListener(new OnTouchListener(){
@Override
public boolean onTouch(View v,MotionEvent event){
rabbit.bitmapX=event.getX();
rabbit.bitmapY=event.getY();
rabbit.invalidate();
return true;
}
});
frameLayout.addView(rabbit);
}
@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;
}
}
RabbitView.java代码
package com.example.test34;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
public class RabbitView extends View {
public float bitmapX;
public float bitmapY;
public RabbitView(Context context){
super(context);
bitmapX=750;
bitmapY=500;
}
@Override
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
Paint paint=new Paint();
Bitmap bitmap=BitmapFactory.decodeResource(this.getResources(),R.drawable.ic_launcher);
canvas.drawBitmap(bitmap,bitmapX,bitmapY,paint);
if(bitmap.isRecycled()){
bitmap.recycle();
}
}
}
activity_main代码
<FrameLayout 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"
android:background="@drawable/background"
android:id="@+id/mylayout" >
logcat为：
07-22 17:27:52.100: D/dalvikvm(11872): GC_EXTERNAL_ALLOC freed 47K, 50% free 2740K/5379K, external 0K/0K, paused 71ms
07-22 17:27:52.120: D/AndroidRuntime(11872): Shutting down VM
07-22 17:27:52.120: W/dalvikvm(11872): threadid=1: thread exiting with uncaught exception (group=0x4001e578)
07-22 17:27:52.120: E/AndroidRuntime(11872): FATAL EXCEPTION: main
07-22 17:27:52.120: E/AndroidRuntime(11872): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test34/com.example.test34.MainActivity}: java.lang.NullPointerException
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.os.Handler.dispatchMessage(Handler.java:99)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.os.Looper.loop(Looper.java:130)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread.main(ActivityThread.java:3691)
07-22 17:27:52.120: E/AndroidRuntime(11872): at java.lang.reflect.Method.invokeNative(Native Method)
07-22 17:27:52.120: E/AndroidRuntime(11872): at java.lang.reflect.Method.invoke(Method.java:507)
07-22 17:27:52.120: E/AndroidRuntime(11872): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
07-22 17:27:52.120: E/AndroidRuntime(11872): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:670)
07-22 17:27:52.120: E/AndroidRuntime(11872): at dalvik.system.NativeStart.main(Native Method)
07-22 17:27:52.120: E/AndroidRuntime(11872): Caused by: java.lang.NullPointerException
07-22 17:27:52.120: E/AndroidRuntime(11872): at com.example.test34.MainActivity.onCreate(MainActivity.java:27)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1050)
07-22 17:27:52.120: E/AndroidRuntime(11872): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
07-22 17:27:52.120: E/AndroidRuntime(11872): ... 11 more
07-22 17:27:54.130: I/dalvikvm(11872): threadid=4: reacting to signal 3
07-22 17:27:54.130: I/dalvikvm(11872): Wrote stack traces to '/data/anr/traces.txt'
