Android自定义控件实现温度旋转按钮效果

public class TempControlView extends View {

 // 控件宽
 private int width;
 // 控件高
 private int height;
 // 刻度盘半径
 private int dialRadius;
 // 圆弧半径
 private int arcRadius;
 // 刻度高
 private int scaleHeight = dp2px(10);
 // 刻度盘画笔
 private Paint dialPaint;
 // 圆弧画笔
 private Paint arcPaint;
 // 标题画笔
 private Paint titlePaint;
 // 温度标识画笔
 private Paint tempFlagPaint;
 // 旋转按钮画笔
 private Paint buttonPaint;
 // 温度显示画笔
 private Paint tempPaint;
 // 文本提示
 private String title = "最高温度设置";
 // 温度
 private int temperature;
 // 最低温度
 private int minTemp = 15;
 // 最高温度
 private int maxTemp = 30;
 // 四格（每格4.5度，共18度）代表温度1度
 private int angleRate = 4;
 // 按钮图片
 private Bitmap buttonImage = BitmapFactory.decodeResource(getResources(),
   R.mipmap.btn_rotate);
 // 按钮图片阴影
 private Bitmap buttonImageShadow = BitmapFactory.decodeResource(getResources(),
   R.mipmap.btn_rotate_shadow);
 // 抗锯齿
 private PaintFlagsDrawFilter paintFlagsDrawFilter;
 // 温度改变监听
 private OnTempChangeListener onTempChangeListener;

 // 以下为旋转按钮相关

 // 当前按钮旋转的角度
 private float rotateAngle;
 // 当前的角度
 private float currentAngle;

 ...

 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  // 控件宽、高
  width = height = Math.min(h, w);
  // 刻度盘半径
  dialRadius = width / 2 - dp2px(20);
  // 圆弧半径
  arcRadius = dialRadius - dp2px(20);
 }

 ...
}

/**
 * 绘制刻度盘
 *
 * @param canvas 画布
 */
private void drawScale(Canvas canvas) {
 canvas.save();
 canvas.translate(getWidth() / 2, getHeight() / 2);
 // 逆时针旋转135-2度
 canvas.rotate(-133);
 dialPaint.setColor(Color.parseColor("#3CB7EA"));
 for (int i = 0; i < 60; i++) {
  canvas.drawLine(0, -dialRadius, 0, -dialRadius + scaleHeight, dialPaint);
  canvas.rotate(4.5f);
 }

 canvas.rotate(90);
 dialPaint.setColor(Color.parseColor("#E37364"));
 for (int i = 0; i < (temperature - minTemp) * angleRate; i++) {
  canvas.drawLine(0, -dialRadius, 0, -dialRadius + scaleHeight, dialPaint);
  canvas.rotate(4.5f);
 }
 canvas.restore();
}

/**
 * 绘制刻度盘下的圆弧
 *
 * @param canvas 画布
 */
private void drawArc(Canvas canvas) {
 canvas.save();
 canvas.translate(getWidth() / 2, getHeight() / 2);
 canvas.rotate(135 + 2);
 RectF rectF = new RectF(-arcRadius, -arcRadius, arcRadius, arcRadius);
 canvas.drawArc(rectF, 0, 265, false, arcPaint);
 canvas.restore();
}

 /**
  * 绘制标题与温度标识
  *
  * @param canvas 画布
  */
 private void drawText(Canvas canvas) {
  canvas.save();

  // 绘制标题
  float titleWidth = titlePaint.measureText(title);
  canvas.drawText(title, (width - titleWidth) / 2, dialRadius * 2 + dp2px(15), titlePaint);

  // 绘制最小温度标识
  // 最小温度如果小于10，显示为0x
  String minTempFlag = minTemp < 10 ? "0" + minTemp : minTemp + "";
  float tempFlagWidth = titlePaint.measureText(maxTemp + "");
  canvas.rotate(55, width / 2, height / 2);
  canvas.drawText(minTempFlag, (width - tempFlagWidth) / 2, height + dp2px(5), tempFlagPaint);

  // 绘制最大温度标识
  canvas.rotate(-105, width / 2, height / 2);
  canvas.drawText(maxTemp + "", (width - tempFlagWidth) / 2, height + dp2px(5), tempFlagPaint);
  canvas.restore();
 }

/**
 * 绘制旋转按钮
 *
 * @param canvas 画布
 */
private void drawButton(Canvas canvas) {
 // 按钮宽高
 int buttonWidth = buttonImage.getWidth();
 int buttonHeight = buttonImage.getHeight();
 // 按钮阴影宽高
 int buttonShadowWidth = buttonImageShadow.getWidth();
 int buttonShadowHeight = buttonImageShadow.getHeight();

 // 绘制按钮阴影
 canvas.drawBitmap(buttonImageShadow, (width - buttonShadowWidth) / 2,
   (height - buttonShadowHeight) / 2, buttonPaint);

 Matrix matrix = new Matrix();
 // 设置按钮位置
 matrix.setTranslate(buttonWidth / 2, buttonHeight / 2);
 // 设置旋转角度
 matrix.preRotate(45 + rotateAngle);
 // 按钮位置还原，此时按钮位置在左上角
 matrix.preTranslate(-buttonWidth / 2, -buttonHeight / 2);
 // 将按钮移到中心位置
 matrix.postTranslate((width - buttonWidth) / 2, (height - buttonHeight) / 2);

 //设置抗锯齿
 canvas.setDrawFilter(paintFlagsDrawFilter);
 canvas.drawBitmap(buttonImage, matrix, buttonPaint);
}

/**
 * 绘制温度
 *
 * @param canvas 画布
 */
private void drawTemp(Canvas canvas) {
 canvas.save();
 canvas.translate(getWidth() / 2, getHeight() / 2);

 float tempWidth = tempPaint.measureText(temperature + "");
 float tempHeight = (tempPaint.ascent() + tempPaint.descent()) / 2;
 canvas.drawText(temperature + "°", -tempWidth / 2 - dp2px(5), -tempHeight, tempPaint);
 canvas.restore();
}

private boolean isDown;
private boolean isMove;

@Override
public boolean onTouchEvent(MotionEvent event) {
 switch (event.getAction()) {
  case MotionEvent.ACTION_DOWN:
   isDown = true;
   float downX = event.getX();
   float downY = event.getY();
   currentAngle = calcAngle(downX, downY);
   break;

  case MotionEvent.ACTION_MOVE:
   isMove = true;
   float targetX;
   float targetY;
   downX = targetX = event.getX();
   downY = targetY = event.getY();
   float angle = calcAngle(targetX, targetY);

   // 滑过的角度增量
   float angleIncreased = angle - currentAngle;

   // 防止越界
   if (angleIncreased < -270) {
    angleIncreased = angleIncreased + 360;
   } else if (angleIncreased > 270) {
    angleIncreased = angleIncreased - 360;
   }

   IncreaseAngle(angleIncreased);
   currentAngle = angle;
   invalidate();
   break;

  case MotionEvent.ACTION_CANCEL:
  case MotionEvent.ACTION_UP: {
   if (isDown && isMove) {
    // 纠正指针位置
    rotateAngle = (float) ((temperature - minTemp) * angleRate * 4.5);
    invalidate();
    // 回调温度改变监听
    onTempChangeListener.change(temperature);
    isDown = false;
    isMove = false;
   }
   break;
  }
 }
 return true;
}

/**
 * 以按钮圆心为坐标圆点，建立坐标系，求出(targetX, targetY)坐标与x轴的夹角
 *
 * @param targetX x坐标
 * @param targetY y坐标
 * @return (targetX, targetY)坐标与x轴的夹角
 */
private float calcAngle(float targetX, float targetY) {
 float x = targetX - width / 2;
 float y = targetY - height / 2;
 double radian;

 if (x != 0) {
  float tan = Math.abs(y / x);
  if (x > 0) {
   if (y >= 0) {
    radian = Math.atan(tan);
   } else {
    radian = 2 * Math.PI - Math.atan(tan);
   }
  } else {
   if (y >= 0) {
    radian = Math.PI - Math.atan(tan);
   } else {
    radian = Math.PI + Math.atan(tan);
   }
  }
 } else {
  if (y > 0) {
   radian = Math.PI / 2;
  } else {
   radian = -Math.PI / 2;
  }
 }
 return (float) ((radian * 180) / Math.PI);
}

/**
 * 增加旋转角度
 *
 * @param angle 增加的角度
 */
private void IncreaseAngle(float angle) {
 rotateAngle += angle;
 if (rotateAngle < 0) {
  rotateAngle = 0;
 } else if (rotateAngle > 270) {
  rotateAngle = 270;
 }
 temperature = (int) (rotateAngle / 4.5) / angleRate + minTemp;
}

/**
 * 设置温度
 *
 * @param minTemp 最小温度
 * @param maxTemp 最大温度
 * @param temp 设置的温度
 */
public void setTemp(int minTemp, int maxTemp, int temp) {
 this.minTemp = minTemp;
 this.maxTemp = maxTemp;
 this.temperature = temp;
 this.angleRate = 60 / (maxTemp - minTemp);
 rotateAngle = (float) ((temp - minTemp) * angleRate * 4.5);
 invalidate();
}

/**
 * 设置温度改变监听
 *
 * @param onTempChangeListener 监听接口
 */
public void setOnTempChangeListener(OnTempChangeListener onTempChangeListener) {
 this.onTempChangeListener = onTempChangeListener;
}

/**
 * 温度改变监听接口
 */
public interface OnTempChangeListener {
 /**
  * 回调方法
  *
  * @param temp 温度
  */
 void change(int temp);
}