Android系列之手机多点触摸画圆

静态效果图：（多个手指按下和抬起的状态）

代码实现部分：

1、先写个实体类，设置相关的属性

package com.zking.laci.android19_pointstouch;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import java.util.Random;/** * Created by Laci on 2017/7/9. */public class MyCircle {    public float x;    public float y;    public int r=100;    public int pointId;    int red;    int green;    int blue;    Random random=new Random();    public MyCircle(float x, float y, int pointId) {        this.x = x;        this.y = y;        this.pointId = pointId;        red=random.nextInt(255);        green=random.nextInt(255);        blue=random.nextInt(255);    }    public void drawSelf(Canvas canvas, Paint paint){        paint.setStyle(Paint.Style.STROKE);        paint.setColor(Color.rgb(red,green,blue));        canvas.drawCircle(x,y,r,paint);    }}

2、然后我们自己再写个java类，用来画圆的

package com.zking.laci.android19_pointstouch;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import java.util.ArrayList;import java.util.List;/** * Created by Laci on 2017/7/9. */public class MyView extends View {    List<MyCircle> lt=new ArrayList<>();    public MyView(Context context) {        super(context);    }    public MyView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {        super(context, attrs, defStyleAttr, defStyleRes);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Paint paint=new Paint();        for (MyCircle myCircle : lt) {            myCircle.drawSelf(canvas,paint);        }    }    @Override    public boolean onTouchEvent(MotionEvent event) {        //获取手指的行为        int action=event.getAction();        int action_code=action&0xff;        //手指的下标        int pointIndex=action>>8;        //获取手指的坐标        float x=event.getX(pointIndex);        float y=event.getY(pointIndex);        //获取手指的名字的ID        int pointId=event.getPointerId(pointIndex);        if(action_code>=5){            action_code-=5;        }        switch (action_code) {            case MotionEvent.ACTION_DOWN:                //实例化园                MyCircle myCircle=new MyCircle(x,y,pointId);                //将园添加到集合中                lt.add(myCircle);                break;            case MotionEvent.ACTION_UP:                lt.remove(get(pointId));                break;            case MotionEvent.ACTION_MOVE:                for (int i = 0; i <event.getPointerCount() ; i++) {                    int id=event.getPointerId(i);                    get(id).x=event.getX(i);                    get(id).y=event.getY(i);                }                break;        }        //重新调用onDraw 重绘        invalidate();        return true;    }    public MyCircle get(int pointId){        for (MyCircle myCircle : lt) {            if(myCircle.pointId==pointId){                return myCircle;            }        }        return null;    }}

3、最后我们在activity中改一句代码就可以了

setContentView(new MyView(this));

最后打开真机测试就可以啦！