<?xml version="1.0" encoding="utf-8"?>
<resources>
 <declare-styleable name="ClockView">
  <attr name="pointer_color" format="color" />
  <attr name="scale_color" format="color" />
  <attr name="one_circle_color" format="color" />
  <attr name="two_circle_color" format="color" />
  <attr name="three_circle_color" format="color" />
  <attr name="four_circle_color" format="color" />
 </declare-styleable>
</resources>

package com.example.helloworld;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.Nullable;

import java.util.Calendar;

/**
 * 时钟
 *
 * @since 2021-02-29
 * @author Sar
 */
public class ClockView extends View {
 private static final int DEFAULT_POINTER_COLOR = Color.parseColor("#FFFFFF");
 private static final int DEFAULT_SCALE_COLOR = Color.parseColor("#FFFFFF");
 private static final int DEFAULT_ONE_CIRCLE_COLOR = Color.parseColor("#FFFFFF");
 private static final int DEFAULT_TWO_CIRCLE_COLOR = Color.parseColor("#CCCCCC");
 private static final int DEFAULT_THREE_CIRCLE_COLOR = Color.parseColor("#BBBBBB");
 private static final int DEFAULT_FOUR_CIRCLE_COLOR = Color.parseColor("#AAAAAA");
 private static final int DEFAULT_FOUR_CIRCLE_DIAMETER = 180; // 默认外圈圆直径，也就是该控件默认宽高，单位dp

 private int pointerColor; // 指针颜色
 private int scaleColor; // 刻度颜色
 private int oneCircleColor; // 中心圆颜色
 private int twoCircleColor; // 次中心圆颜色
 private int threeCircleColor; // 次外圈圆颜色
 private int fourCircleColor; // 外圈圆颜色

 private Paint paint;

 private int cx;
 private int cy;
 private int scaleStrokeWidth;
 private int hourPointerWidth;
 private int minutePointerWidth;
 private int oneCircleDiameter;
 private int twoCircleDiameter;
 private int threeCircleDiameter;
 private int fourCircleDiameter;
 private int defaultFourCircleDiameter;

 public ClockView(Context context) {
  super(context);
  init(context, null, 0);
 }

 public ClockView(Context context, @Nullable AttributeSet attrs) {
  super(context, attrs);
  init(context, attrs, 0);
 }

 public ClockView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init(context, attrs, defStyleAttr);
 }

 private void init(Context context, AttributeSet attrs, int defStyleAttr) {
  if (attrs != null) {
   TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ClockView, defStyleAttr, 0);
   pointerColor = typedArray.getColor(R.styleable.XTClockView_pointer_color, DEFAULT_POINTER_COLOR);
   scaleColor = typedArray.getColor(R.styleable.XTClockView_scale_color, DEFAULT_SCALE_COLOR);
   oneCircleColor = typedArray.getColor(R.styleable.XTClockView_one_circle_color, DEFAULT_ONE_CIRCLE_COLOR);
   twoCircleColor = typedArray.getColor(R.styleable.XTClockView_two_circle_color, DEFAULT_TWO_CIRCLE_COLOR);
   threeCircleColor = typedArray.getColor(R.styleable.XTClockView_three_circle_color, DEFAULT_THREE_CIRCLE_COLOR);
   fourCircleColor = typedArray.getColor(R.styleable.XTClockView_four_circle_color, DEFAULT_FOUR_CIRCLE_COLOR);
   typedArray.recycle();
  } else {
   pointerColor = DEFAULT_POINTER_COLOR;
   scaleColor = DEFAULT_SCALE_COLOR;
   oneCircleColor = DEFAULT_ONE_CIRCLE_COLOR;
   twoCircleColor = DEFAULT_TWO_CIRCLE_COLOR;
   threeCircleColor = DEFAULT_THREE_CIRCLE_COLOR;
   fourCircleColor = DEFAULT_FOUR_CIRCLE_COLOR;
  }
  paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  paint.setStyle(Paint.Style.FILL);
  defaultFourCircleDiameter = dp2px(context, DEFAULT_FOUR_CIRCLE_DIAMETER);
 }
 
 public void setPointerColor(int pointerColor) {
  this.pointerColor = pointerColor;
 }

 public void setScaleColor(int scaleColor) {
  this.scaleColor = scaleColor;
 }

 public void setOneCircleColor(int oneCircleColor) {
  this.oneCircleColor = oneCircleColor;
 }

 public void setTwoCircleColor(int twoCircleColor) {
  this.twoCircleColor = twoCircleColor;
 }

 public void setThreeCircleColor(int threeCircleColor) {
  this.threeCircleColor = threeCircleColor;
 }

 public void setFourCircleColor(int fourCircleColor) {
  this.fourCircleColor = fourCircleColor;
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  int width = 0;
  int height = 0;
  int widthMode = MeasureSpec.getMode(widthMeasureSpec);
  int widthSize = MeasureSpec.getSize(widthMeasureSpec);
  switch (widthMode) {
   case MeasureSpec.EXACTLY:
    width = widthSize;
    break;
   case MeasureSpec.AT_MOST:
   case MeasureSpec.UNSPECIFIED:
    width = defaultFourCircleDiameter;
    break;
  }
  int heightMode = MeasureSpec.getMode(heightMeasureSpec);
  int heightSize = MeasureSpec.getSize(heightMeasureSpec);
  switch (heightMode) {
   case MeasureSpec.EXACTLY:
    height = heightSize;
    break;
   case MeasureSpec.AT_MOST:
   case MeasureSpec.UNSPECIFIED:
    height = defaultFourCircleDiameter;
    break;
  }
  setMeasuredDimension(width, height);
  cx = width / 2;
  cy = height / 2;
  fourCircleDiameter = Math.min(width, height);
  threeCircleDiameter = fourCircleDiameter * 7 / 10;
  twoCircleDiameter = fourCircleDiameter * 28 / 50;
  oneCircleDiameter = fourCircleDiameter * 3 / 50;
  scaleStrokeWidth = fourCircleDiameter / 100;
  hourPointerWidth = oneCircleDiameter * 2 / 5;
  minutePointerWidth = oneCircleDiameter / 5;
 }

 private int dp2px(Context context, int dpValue) {
  float scale = context.getResources().getDisplayMetrics().density;
  return (int) (dpValue * scale + 0.5f);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  drawCircle(canvas, fourCircleColor, fourCircleDiameter);
  drawCircle(canvas, threeCircleColor, threeCircleDiameter);
  drawCircle(canvas, twoCircleColor, twoCircleDiameter);

  drawScale(canvas);
  Calendar calendar = Calendar.getInstance();
  calendar.setTimeInMillis(System.currentTimeMillis());
  int hour = calendar.get(Calendar.HOUR);
  int minute = calendar.get(Calendar.MINUTE);
  int second = calendar.get(Calendar.SECOND);

  paint.setColor(pointerColor);
  drawPointer(canvas, (float) (hour * 30 + minute * 0.5), hourPointerWidth, cy - twoCircleDiameter / 2 * 2 / 3);
  drawPointer(canvas, minute * 6, minutePointerWidth, cy - twoCircleDiameter / 2 * 4 / 5);
  drawPointer(canvas, second * 6, minutePointerWidth, cy - twoCircleDiameter / 2 * 8 / 9);

  paint.setStrokeWidth(0);
  drawCircle(canvas, oneCircleColor, oneCircleDiameter);

  postInvalidateDelayed(1000);
 }

 private void drawCircle(Canvas canvas, int circleColor, int circleDiameter) {
  paint.setColor(circleColor);
  canvas.drawCircle(cx, cy, circleDiameter / 2, paint);
 }

 private void drawScale(Canvas canvas) {
  paint.setColor(scaleColor);
  paint.setStrokeWidth(scaleStrokeWidth);
  for (int i = 0; i < 12; i++) {
   canvas.save();
   canvas.rotate(i * 30, cx, cy);
   canvas.drawLine(cx, (fourCircleDiameter - threeCircleDiameter) / 6, cx, (fourCircleDiameter - threeCircleDiameter) / 3, paint);
   canvas.restore();
  }
 }

 private void drawPointer(Canvas canvas, float rotateDegrees, float strokeWidth, float stopY) {
  paint.setStrokeWidth(strokeWidth);
  canvas.save();
  canvas.rotate(rotateDegrees, cx, cy);
  canvas.drawLine(cx, cy, cx, stopY, paint);
  canvas.restore();
 }
}

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