Android使用surfaceView自定义抽奖大转盘

private SurfaceHolder mSurfaceHolder;
private Canvas    mCanvas;

public SurfaceViewTemplate(Context context,AttributeSet attrs) {
  super(context, attrs);
  //初始化
  mSurfaceHolder = getHolder();
  mSurfaceHolder.addCallback(this);
  //设置可获得焦点
  setFocusable(true);
  setFocusableInTouchMode(true);
  //这是常亮
  setKeepScreenOn(true);
}

 @Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
  //surface创建的时候
  mThread = new Thread(this);
  //创建的时候就开启线程
  isRunning = true;
  mThread.start();
}

@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
  //变化的时候
}

@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
  //销毁的时候 关闭线程
  isRunning = false;
}

 @Override
public void run() {
  //在子线程中不断的绘制
  while (isRunning) {
    draw();
  }
}

private void draw() {
  try {
    mCanvas = mSurfaceHolder.lockCanvas();
    if (null != mCanvas) {
  //避免执行到这里的时候程序已经退出 surfaceView已经销毁那么获取到canvas为null
    }
  } catch (Exception e) {
    //异常可以不必处理
  } finally {
    //一定要释放canvas避免泄露
    mSurfaceHolder.unlockCanvasAndPost(mCanvas);
  }
}

@Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    //直接控制Span为正方形
    int width = Math.min(getMeasuredWidth(), getMeasuredHeight());
    mPadding = getPaddingLeft();
    //直径
    mRadius = width - mPadding * 2;
    //设置中心点
    mCenter = width / 2;
    //设置成正方形
    setMeasuredDimension(width, width);
  }

public void surfaceCreated(SurfaceHolder surfaceHolder) {
    //初始化绘制Span的画笔
    mSpanPaint = new Paint();
    mSpanPaint.setAntiAlias(true);
    mSpanPaint.setDither(true);
    //初始化绘制文本的画笔
    mTextPaint = new Paint();
    mTextPaint.setTextSize(mTextSize);
    mTextPaint.setColor(0Xffa58453);
    //绘制圆环的画笔
    mCirclePaint = new Paint();
    mCirclePaint.setAntiAlias(true);
    mCirclePaint.setColor(0xffdfc89c);
    //初始化Span的范围
    mRectRange = new RectF(mPadding, mPadding, mPadding + mRadius, mPadding + mRadius);
    mRectCircleRange = new RectF(mPadding * 3 / 2, mPadding * 3 / 2, getMeasuredWidth() - mPadding * 3 / 2, getMeasuredWidth() - mPadding * 3 / 2);
    //初始化bitmap
    mImgIconBitmap = new Bitmap[mSpanCount];
    //将奖项的icon存储为Bitmap
    for (int i = 0; i < mSpanCount; i++) {
      mImgIconBitmap[i] = BitmapFactory.decodeResource(getResources(), mPrizeIcon[i]);
    }

    //surface创建的时候
    mThread = new Thread(this);
    //创建的时候就开启线程
    isRunning = true;
    mThread.start();
  }

 @Override
  public void run() {
    //在子线程中不断的绘制
    while (isRunning) {
      //保证绘制不低于50毫秒 优化性能
      long start = SystemClock.currentThreadTimeMillis();
      draw();
      long end = SystemClock.currentThreadTimeMillis();
      if ((end - start) < 50) {
        //休眠到50毫秒
        SystemClock.sleep(50 - (end - start));
      }
    }
  }

 try {
    mCanvas = mSurfaceHolder.lockCanvas();
    if (null != mCanvas) {
      //避免执行到这里的时候程序已经退出 surfaceView已经销毁那么获取到canvas为null
      //绘制背景
      drawBg();
      //绘制圆环
      mCanvas.drawCircle(mCenter, mCenter, mRadius / 2 + mPadding / 20, mCirclePaint);
      drawSpan();
    }
  } catch (Exception e) {
    //异常可以不必处理
  } finally {
    //一定要释放canvas避免泄露
    mSurfaceHolder.unlockCanvasAndPost(mCanvas);
  }

//绘制背景
  private void drawBg() {
    //背景设置为白色
    mCanvas.drawColor(0xffffffff);
    mCanvas.drawBitmap(mSpanBackground, null, new RectF(mPadding / 2, mPadding / 2, getMeasuredWidth() - mPadding / 2, getMeasuredHeight() - mPadding / 2), mSpanPaint);
  }

  mSpanBackground背景图片
  new RectF(mPadding / 2, mPadding / 2, getMeasuredWidth() - mPadding / 2, getMeasuredHeight() - mPadding / 2)
  //限制背景在一个矩形范围之类 

mCanvas.drawCircle(mCenter, mCenter, mRadius / 2 + mPadding / 20, mCirclePaint); 

//定义一个变量临时记录开始转动的角度
float tempAngle = mStartSpanAngle;
//每个盘块所占的角度 CIRCLE_ANGLE = 360
float sweepAngle = CIRCLE_ANGLE / mSpanCount;
//循环绘制八个板块
  for (int i = 0; i < mSpanCount; i++) {
    //设置每个盘块画笔的颜色
    mSpanPaint.setColor(mSpanColor[i]);
    //绘制扇形盘块，第四个参数为true就是扇形否则就是弧形
    mCanvas.drawArc(mRectCircleRange, tempAngle, sweepAngle, true, mSpanPaint);
    //绘制文字
    drawText(tempAngle, sweepAngle, mPrizeName[i]);
    //绘制奖项Icon
    drawPrizeIcon(tempAngle, mImgIconBitmap[i]);
      //改变角度
      tempAngle += sweepAngle;
    }

private void drawText(float tempAngle, float sweepAngle, String text) {
  //绘制有弧度的文字 根据path绘制文字的路径
  Path path = new Path();
  path.addArc(mRectRange, tempAngle, sweepAngle);
  //让文字水平居中 那绘制文字的起点位子就是 弧度的一半 - 文字的一半
  float textWidth = mTextPaint.measureText(text);
  float hOval = (float) ((mRadius * Math.PI / mSpanCount / 2) - (textWidth / 2));

  float vOval = mRadius / 15;//竖直偏移量可以自定义

  mCanvas.drawTextOnPath(text, path, hOval, vOval, mTextPaint); //第三个四个参数是竖直和水平偏移量
}

private void drawPrizeIcon(float tempAngle, Bitmap bitmap) {
  //图片的大小设置成直径的1/8
  int iconWidth = mRadius / 20;
  //根据角度计算icon中心点
  //角度计算 1度 == Math.PI / 180
  double angle = (tempAngle + CIRCLE_ANGLE / mSpanCount / 2) * Math.PI / 180;
  //根据三角函数，计算中心点(x,y)
  int x = (int) (mCenter + mRadius / 4 * Math.cos(angle));
  int y = (int) (mCenter + mRadius / 4 * Math.sin(angle));
  //定义一个矩形 限制icon位置
  RectF rectF = new RectF(x - iconWidth, y - iconWidth, x + iconWidth, y + iconWidth);
  mCanvas.drawBitmap(bitmap, null, rectF, null);
}

 mStartSpanAngle += mSpeed;//mSpeed的数值控制转动的速度
   //声明的一个结束标志
  if (isSpanEnd) {
    mSpeed -= 1;
  }
  if (mSpeed <= 0) {
    //停止旋转了
    mSpeed = 0;
    isSpanEnd = false;
    //定义一个回调，监控转盘停止转动
   mSpanRollListener.onSpanRollListener(mSpeed);
  }

//抽奖转盘重点就在这里，根据自己传入的index控制抽到的奖品
public void luckyStart(int index) {
  //根据index控制停留的位置 angle 是每个奖品所占的角度范围
  float angle = CIRCLE_ANGLE / mSpanCount;
  //计算指针停留在某个index下的角度范围HALF_CIRCLE_ANGLE=180度
  float from = HALF_CIRCLE_ANGLE - (index - 1) * angle;
  float end = from + angle;

  //设置需要停下来的时候转动的距离 保证每次不停留的某个index下的同一个位置
  float targetFrom = 4 * CIRCLE_ANGLE + from;
  float targetEnd = 4 * CIRCLE_ANGLE + end;//最终停下来的位置在from-end之间，4 * CIRCLE_ANGLE 自定义要多转几圈

  //计算要停留下来的时候速度的范围，这里注意：涉及到等差数列的公式，因为涉及到让转盘停止转动是使mSpeed-=1；所以它是从 vFrom--0等差递减的一个过程，所以可以算出来vFrom，同理计算出vEnd
  float vFrom = (float) ((Math.sqrt(1 + 8 * targetFrom) - 1) / 2);
  float vEnd = (float) ((Math.sqrt(1 + 8 * targetEnd) - 1) / 2);
  //在点击开始转动的时候 传递进来的index值就已经决定停留在那一项上面了
  mSpeed = vFrom + Math.random() * (vEnd - vFrom);
  isSpanEnd = false;
}

 public void luckStop() {
  //在停止转盘的时候强制吧开始角度赋值为0 因为控制停留指定位置的角度计算是根据开始角度为0计算的
  mStartSpanAngle = 0;
  isSpanEnd = true;
}