【备忘】Android模拟小球自由落体（SurfaceView）

package com.example.sft;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;

public class TestSurfaceView extends SurfaceView implements SurfaceHolder.Callback{
    
    private Paint cp;
    private List<KCircle> KCList;
    private Random r;

    public TestSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        getHolder().addCallback(this);
        cp=new Paint();
        cp.setColor(Color.BLACK);
        KCList=new ArrayList<KCircle>();
        r=new Random();
    }

    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
        // TODO Auto-generated method stub
        
    }

    private int getRandomColor(){
        return r.nextInt()%0xff000000;
    }
    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        // TODO Auto-generated method stub
        
        
    }
    
    /**
     * 
     */
    public void run(){
        new MyThread().start();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {
        // TODO Auto-generated method stub
        
    }
    
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // TODO Auto-generated method stub
         if (event.getAction() != MotionEvent.ACTION_DOWN &&
                 event.getAction() != MotionEvent.ACTION_MOVE) {
             return false;
         }
        KCList.add(new KCircle(getRandomColor(),(int)event.getX(),(int)event.getY()));
        return true;
    }
    
    class MyThread extends Thread{
        @Override
        public void run() {
            // TODO Auto-generated method stub
            while(true){
            Canvas c=getHolder().lockCanvas();
            c.drawPaint(cp);
            for(int i=0;i<KCList.size();i++){
                KCList.get(i).moveAndDraw(c);
                if(KCList.get(i).y>getHeight()){
                    KCList.remove(i);
                }
            }
            
            try {
                sleep(15);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
            getHolder().unlockCanvasAndPost(c);
            }
            
        }
    }
    
    
}

package com.example.sft;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;


public class KCircle {
    
    private int color;
    public int x;
    public int y;
    private Paint p;
    private int radius;
    int v;
    int a;
    
    
    public KCircle(int color){
        this.color=color;
        x=0;
        y=0;
        v=0;
        a=2;
        radius=25;
        p=new Paint();
        p.setColor(color);
        RadialGradient rg=new RadialGradient(x+10, y-10, 25,color+(0xffffffff-color)/2, color, Shader.TileMode.CLAMP);
        
        p.setShader(rg);
        p.setAntiAlias(true);
    }
    
    public KCircle(int colcr,int x,int y){
        this(colcr);
        this.x=x;
        this.y=y;
    }
    
    public void moveAndDraw(Canvas c){
        y+=v;
        v+=a;
        draw(c);
    }
    
    public void moveTo(int x,int y){
        this.x=x;
        this.y=y;
    }
    
    public void draw(Canvas c){
        RadialGradient rg=new RadialGradient(x+10, y-10, 25,0xffdddddd, color, Shader.TileMode.CLAMP);
        p.setShader(rg);
        c.drawCircle(x, y, radius, p);

    }
    

}

把TestSurfaceView放入Activity显示出来  然后调用run方法   手指点击的地方就会有小球落下