自定义view实现刮刮乐的效果

package com.example.fw.view;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.TextView;

import com.example.fwzk1.R;

/**
 * Created by 小薇 on 2018/7/9.
 */

public class MyViewPager extends android.support.v7.widget.AppCompatTextView{

    private Paint mpaint;
    private Path path;
    private Bitmap bdbitmap;
    private Bitmap bdcreatebitmap;
    private Canvas mcanvas;
    private Paint textpaint;
    public MyViewPager(Context context) {
        super(context);
        init();
    }

    public MyViewPager(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyViewPager(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
    private void init() {
        //创建画笔，开始实现view
        mpaint = new Paint();
        //透明度
        mpaint.setAlpha(0);
        //设置填充
        mpaint.setStrokeWidth(50);
        //设置样式
        mpaint.setStyle(Paint.Style.STROKE);
        //去两层绘制交集，显示下层
        mpaint.setXfermode(new PorterDuffXfermode((PorterDuff.Mode.DST_IN)));
        mpaint.setStrokeJoin(Paint.Join.ROUND);
        mpaint.setStrokeCap(Paint.Cap.ROUND);
        //设置要刮的路径
        path = new Path();
        //初始化要覆盖的内容
        bdbitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ll);
        //初始化用来做覆盖
        bdcreatebitmap = Bitmap.createBitmap(bdbitmap.getWidth(), bdbitmap.getHeight(), Bitmap.Config.ARGB_8888);

        //初始化画布
        mcanvas = new Canvas(bdcreatebitmap);
        //初始化画笔,写字
        textpaint = new Paint();
        textpaint.setColor(Color.WHITE);
        textpaint.setTextSize(100);
        textpaint.setStrokeWidth(20);
         //画布的颜色
        mcanvas.drawColor(Color.GRAY);
        //设置画布上的字
        mcanvas.drawText("刮刮看咯",mcanvas.getWidth()/4,mcanvas.getHeight()/2,textpaint);

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                //清空画笔
                path.reset();
                //手指移动
                path.moveTo(event.getX(),event.getY());
                break;
            case MotionEvent.ACTION_MOVE:
                //手指移动
                path.lineTo(event.getX(),event.getY());
                break;
        }
        //模拟刮来效果
        mcanvas.drawPath(path,mpaint);
        //刷新
        invalidate();
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //画布
        canvas.drawBitmap(bdbitmap,0,0,null);
        canvas.drawBitmap(bdcreatebitmap,0,0,null);
    }
}