android 多点触摸（实现按下画圆，抬起消失的dome）

来源：互联网发布：mac teamviewer 编辑：程序博客网时间：2024/05/21 08:39

这次呢，我们来做一个dome，使用多点触摸实现按下画圆，抬起消失的效果

我们先来缕一下思路：我们可以有一个圆的实体类，里面定义好圆的圆心坐标，半径，颜色，透明度的属性，具体代码如下：

package com.example.g160628_15;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.view.View;import java.util.Random;/** * Created by Administrator on 2017/7/9 0009. */public class Circle {    public float x;    public float y;    public int r = 100;    public int pointId;    int red;    int green;    int blue;    Random random=new Random();    public Circle(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.setColor(Color.rgb(red,green,blue));        canvas.drawCircle(x,y,r,paint);    }}

我们有了这个实体类之后就是需要自定义UI来实现效果了，我们的思路是这样的，判断你的手指行动是按下，还是抬起，还是移动，然后分别执行不同代码即可，具体代码如下：

package com.example.g160628_15;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 Administrator on 2017/7/9 0009. */public class MyView extends View{    List<Circle> circles=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 (Circle circle : circles) {            circle.drawSelf(canvas,paint);        }    }    @Override    public boolean onTouchEvent(MotionEvent event) {        int action  = event.getAction();        int action_code = action&0xff;        int pointIndex=action>>8;        float x = event.getX(pointIndex);        float y = event.getY(pointIndex);        int pointId = event.getPointerId(pointIndex);        if(action_code>=5){            action_code-=5;        }        switch (action_code){            case MotionEvent.ACTION_DOWN:                //实例化圆                Circle circle=new Circle(x,y,pointId);                //将圆添加到集合中                circles.add(circle);                break;            case MotionEvent.ACTION_UP:                circles.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;        }        invalidate();        return true;    }    public Circle get(int pointId){        for (Circle circle : circles) {            if(circle.pointId==pointId){                return circle;            }        }        return null;    }}

然后是主Activity

package com.example.g160628_15;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(new MyView(this));    }}

至此，我们的效果就实现了，你还可以用这个dome检测你的手机有多少个触摸点哦

阅读全文

0 0