自定义View，放大缩小框

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package com.fpt.drawlineview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

public class DrawCircleAdd extends View {
    private Paint paint;
    private Path path;
    private int x1,y1,x2,y2,x3,y3,x4,y4;
    private int[] move1,move2;
    private int lengx,lengy,baselength,length;
    public DrawCircleAdd(Context context) {
        super(context);
        initData();
    }

    public DrawCircleAdd(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initData();
    }

    public DrawCircleAdd(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initData();
    }

    public DrawCircleAdd(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        initData();
    }
    public void initData(){
        paint=new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.YELLOW);
        paint.setStrokeWidth(3);

        path=new Path();
        x1=60;y1=500;
        x2=40;y2=700;
        x3=240;y3=500;
        x4=260;y4=700;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        path.reset();
        path.moveTo(x1,y1);
        path.lineTo(x2,y2);
        path.lineTo(x4,y4);
        path.lineTo(x3,y3);
        path.close();
        canvas.drawPath(path,paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                break;
            case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount()==2){//该判断放到down中，是监听不了的，只有这个地方可以监听
                    if (baselength==0) {
                        move1 = new int[]{(int) event.getX(0), (int) event.getY(0)};
                        move2 = new int[]{(int) event.getX(1), (int) event.getY(1)};
                        lengx = Math.abs(move2[0] - move1[0]);
                        lengy = Math.abs(move2[1] - move1[1]);
                        baselength = (int) Math.sqrt(lengx * lengx + lengy * lengy);
                        Log.e("event", "baselength:" + baselength);
                    }else {
                        move1 = new int[]{(int) event.getX(0), (int) event.getY(0)};
                        move2 = new int[]{(int) event.getX(1), (int) event.getY(1)};
                        lengx = Math.abs(move2[0] - move1[0]);
                        lengy = Math.abs(move2[1] - move1[1]);
                        length = (int) Math.sqrt(lengx * lengx + lengy * lengy);
                        length=length-baselength;
                        if (length<0){
                            updataCoorida(-1*3);//*3表示加速级别
                        }else {
                            updataCoorida(1*3);//*3表示加速级别
                        }
                        Log.e("event", "length:" + length);
                        baselength=0;//画龙点睛，精彩
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
                length=0;
                break;
        }
        return true;
    }
    public void updataCoorida(int number){
        this.x1=x1-number;
        this.x2=x2-number;
        this.x3=x3+number;
        this.x4=x4+number;
        this.y1=y1-number;
        this.y3=y3-number;
        this.y2=y2+number;
        this.y4=y4+number;
        invalidate();//重新调用onDraw
    }
}