主要思想：

將一個(gè)view設(shè)計(jì)成多層：背景層，含中獎(jiǎng)信息等；

遮蓋層，用于刮獎(jiǎng)，使用關(guān)聯(lián)一個(gè)Bitmap的Canvas

在該Bitmap上，使用它的canvas.drawPath的api來(lái)處理 手勢(shì)滑動(dòng)(類(lèi)似刮獎(jiǎng)的動(dòng)作)

使用paint.setXfermode 來(lái)進(jìn)行消除手勢(shì)滑動(dòng)區(qū)域

public class GuaView extends View {

private Bitmap mBitmap; //遮蓋的圖層

private Canvas mCanvas; //繪制遮蓋圖層

private Paint mOuterPaint;

private Path mPath;

private float mLastX;

private float mLastY;

private Bitmap mCoverBitmap; //遮蓋圖

private int mWidth,mHeight;

private Paint mInnerPaint;

private String mInfo;

public GuaView(Context context) {

this(context,null);

}

public GuaView(Context context,AttributeSet attrs) {

super(context,attrs);

init();

}

private void init() {

mPath = new Path();

mOuterPaint = new Paint();

mInnerPaint = new Paint();

mCoverBitmap = BitmapFactory.decodeResource(getResources(),R.drawable.fg_guaguaka);

mInfo = "￥ 5 0 0";

}

@Override

protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec,heightMeasureSpec);

mWidth = mCoverBitmap.getWidth();

mHeight = mCoverBitmap.getHeight();

setMeasuredDimension(mWidth,mHeight);

mBitmap = Bitmap.createBitmap(mWidth,mHeight,Bitmap.Config.ARGB_8888);

mCanvas = new Canvas(mBitmap);

mCanvas.drawBitmap(mCoverBitmap,null);

setOuterPaint();

setInnerPaint();

}

private void setInnerPaint() {

mInnerPaint.setColor(Color.RED);

mInnerPaint.setStyle(Paint.Style.STROKE);

mInnerPaint.setStrokeCap(Paint.Cap.ROUND);

mInnerPaint.setStrokeJoin(Paint.Join.ROUND);

mInnerPaint.setAntiAlias(true);

mInnerPaint.setDither(true); //防抖

mInnerPaint.setStrokeWidth(5);

mInnerPaint.setTextSize(100);

mInnerPaint.setTextAlign(Paint.Align.CENTER);

}

private void setOuterPaint() {

mOuterPaint.setColor(Color.GREEN);

mOuterPaint.setStyle(Paint.Style.STROKE);

mOuterPaint.setStrokeCap(Paint.Cap.ROUND);

mOuterPaint.setStrokeJoin(Paint.Join.ROUND);

mOuterPaint.setAntiAlias(true);

mOuterPaint.setDither(true); //防抖

mOuterPaint.setStrokeWidth(20);

}

@Override //Path

public boolean onTouchEvent(MotionEvent event) {

float x = event.getX();

float y = event.getY();

switch (event.getAction()) {

case MotionEvent.ACTION_DOWN:

mLastX = x;

mLastY = y;

mPath.moveTo(x,y);

break;

case MotionEvent.ACTION_MOVE:

float deltaX = Math.abs(x - mLastX);

float deltaY = Math.abs(y - mLastY);

if (deltaX > 5 || deltaY > 5) {

mPath.lineTo(x,y);

}

mLastX = x;

mLastY = y;

break;

case MotionEvent.ACTION_UP:

break;

}

invalidate();//調(diào)用onDraw

return true;

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

canvas.drawColor(Color.parseColor("#bbbbbb")); //背景底色 灰色

canvas.drawText(mInfo,mWidth / 2,mHeight / 4 * 3,mInnerPaint); //繪制文本

canvas.drawBitmap(mBitmap,null); //繪制mBitmap 這是一個(gè)可變的bitmap，通過(guò)mCanvas繪制，首先繪制了mCoverBitmap

drawPath();

}

private void drawPath() {

//使用該mode：dst和src相交后， 只保留dst，且除去相交的部份

mOuterPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));

mCanvas.drawPath(mPath,mOuterPaint);

}

}

Paint.Join 連續(xù)畫(huà)筆銜接時(shí)：

MITER 在外邊緣以一個(gè)銳角連接

ROUND 以圓弧

BEVEL 以直線

Paint.Cap 指定對(duì)于 線和路徑(lines and paths) 的開(kāi)始和結(jié)束點(diǎn)的處理方式：

BUTT? ends with the path? 不超越它

ROUND? with the center at the end of the path 半圓

SQUARE? with the center at the end of the path 方形

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