带回弹的开关，音量加减开关

近期做项目需要实现类似车辆控制音量加减的回弹开关，实现对监控zoom的控制。具体效果如下图。
代码已付上。感觉可用点个赞吧。

效果如图

u4cbh-gqaiw.gif

代码如下

/**
 * zoom view
 *
 * @author zhj
 */
public class ZoomView extends View {
    /**
     * 画笔
     */
    private Paint paint;
    /**
     * 点
     */
    private Point mRockerPosition, mCenterPoint;
    /**
     * bitmap
     */
    private Bitmap mAreaBitmap, mThumbBitmap;
    /**
     * size
     */
    private int mHeight, mWidth, mThumbWidth, mThumbHeight, distance;
    /**
     * 动作
     */
    private int action;
    private OnZoomChangeListener changeListener;

    public ZoomView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 移动区域画笔
        paint = new Paint();
        paint.setAntiAlias(true);
        // 中心点
        mCenterPoint = new Point();
        mRockerPosition = new Point();

        mAreaBitmap = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.ic_video_zoom_bg);
        mThumbBitmap = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.ic_video_zoom_contrl);
        mHeight = mAreaBitmap.getHeight();
        mWidth = mAreaBitmap.getWidth();
        mThumbWidth = mThumbBitmap.getWidth();
        mThumbHeight = mThumbBitmap.getHeight();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int measureWidth, measureHeight;
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if (widthMode == MeasureSpec.EXACTLY) {
            measureWidth = widthSize;
        } else {
            measureWidth = mWidth;
        }
        if (heightMode == MeasureSpec.EXACTLY) {
            measureHeight = heightSize;
        } else {
            measureHeight = mHeight;
        }
        setMeasuredDimension(measureWidth, measureHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int cx = getMeasuredWidth() / 2;
        int cy = getMeasuredHeight() / 2;
        // 中心点
        mCenterPoint.set(cx, cy);
        if (0 == mRockerPosition.x || 0 == mRockerPosition.y) {
            mRockerPosition.set(mCenterPoint.x, mCenterPoint.y);
        }
        canvas.drawBitmap(mAreaBitmap, mCenterPoint.x - (mWidth >> 1),
                mCenterPoint.y - (mHeight >> 1), paint);

        canvas.drawBitmap(mThumbBitmap, mRockerPosition.x - (mThumbWidth >> 1),
                mRockerPosition.y - (mThumbHeight >> 1), paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                action = -1;
                break;
            case MotionEvent.ACTION_MOVE:
                mRockerPosition = getRockerPositionPoint(mCenterPoint,
                        new Point((int) event.getX(), (int) event.getY()));
                moveRocker(mRockerPosition.x, mRockerPosition.y);
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                if (changeListener != null && action != -1) {
                    changeListener.onZoom(false, action);
                }
                moveRocker(mCenterPoint.x, mCenterPoint.y);
                break;
            default:
                break;
        }
        return true;
    }

    /**
     * 获取摇杆实际要显示的位置（点）
     *
     * @param centerPoint 中心点
     * @param touchPoint  触摸点
     * @return 摇杆实际显示的位置（点）
     */
    private Point getRockerPositionPoint(Point centerPoint, Point touchPoint) {
        int tempHeight = getMeasuredHeight();
        if (tempHeight > mHeight) {
            tempHeight = mHeight;
        }
        distance = tempHeight / 4;
        int y = touchPoint.y;
        if (y < centerPoint.y - tempHeight / 2 + mThumbHeight / 2) {
            y = centerPoint.y - tempHeight / 2 + mThumbHeight / 2;
        }
        if (y <= 0) {
            y = 1;
        }
        if (y >= centerPoint.y + tempHeight / 2 - mThumbHeight / 2) {
            y = centerPoint.y + tempHeight / 2 - mThumbHeight / 2;
        }
        int state = -1;
        if (y < centerPoint.y - distance) {
            state = 0;
        } else if (y > centerPoint.y + distance) {
            state = 1;
        }
        if (changeListener != null) {
            if (state != -1 && action != state) {
                action = state;
                changeListener.onZoom(true, action);
            }
        }
        return new Point(centerPoint.x, y);
    }

    /**
     * 移动摇杆到指定位置
     *
     * @param x x坐标
     * @param y y坐标
     */
    private void moveRocker(float x, float y) {
        mRockerPosition.set((int) x, (int) y);
        invalidate();
    }

    /**
     * change
     *
     * @param changeListener
     */
    public void setChangeListener(OnZoomChangeListener changeListener) {
        this.changeListener = changeListener;
    }

    /**
     * zoom
     */
    public interface OnZoomChangeListener {

        /**
         * zoom 改变
         *
         * @param start  s
         * @param action a
         */
        void onZoom(boolean start, int action);
    }
}

资源文件

ic_video_zoom_bg.png ic_video_zoom_contrl.png