近日有朋友问我有没有如下图效果的开源控件

相信大家无论是用IOS还是Android,都对这种效果不陌生，很多主流APP都会有这样或类似的效果，之前也打算研究一下这类控件的代码，苦于一直不知道应该怎么搜索这种效果(就是关键词)或者所搜的结果不是自己想要的，所以就一直搁置了下来。

正好朋友需要这种效果，所以就忙里偷闲写了一个类似的、更加常见和适用范围更多的控件，效果如下图所示：

自定义上图所示效果的控件时，其实就是用Canvas绘制不同效果，比如渐变圆弧背景、圆周白色分割线、中间文字等，这篇博客也根据绘制的顺序依次阐述。

1.自定义CircleProgressBar，继承View，并实现响应的构造函数

代码如下：

/** * Created by WangChunLei on 2016.1.16 * E-mail:wcl_android@163.com */public class GradientProgressBar extends View { public GradientProgressBar(Context context) { super(context); init(); } public GradientProgressBar(Context context, AttributeSet attrs) { super(context, attrs); init(); } public GradientProgressBar(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(); }}

其中init方法是对相关画笔进行初始化的方法，init方法代码如下：

private void init() { backCirclePaint = new Paint(); backCirclePaint.setStyle(Paint.Style.STROKE); backCirclePaint.setAntiAlias(true); backCirclePaint.setColor(Color.LTGRAY); backCirclePaint.setStrokeWidth(circleBorderWidth);// backCirclePaint.setMaskFilter(new BlurMaskFilter(20, BlurMaskFilter.Blur.OUTER)); gradientCirclePaint = new Paint(); gradientCirclePaint.setStyle(Paint.Style.STROKE); gradientCirclePaint.setAntiAlias(true); gradientCirclePaint.setColor(Color.LTGRAY); gradientCirclePaint.setStrokeWidth(circleBorderWidth); linePaint = new Paint(); linePaint.setColor(Color.WHITE); linePaint.setStrokeWidth(5); textPaint = new Paint(); textPaint.setAntiAlias(true); textPaint.setTextSize(textSize); textPaint.setColor(Color.BLACK); }

2.测量控件的宽高-onMeasure

onMeasure是自定义控件的第一步，目的就是测量得到该控件应该占有的宽高尺寸。其中onMeasure方法的代码如下：

@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int measureWidth = MeasureSpec.getSize(widthMeasureSpec); int measureHeight = MeasureSpec.getSize(heightMeasureSpec); setMeasuredDimension(Math.min(measureWidth, measureHeight), Math.min(measureWidth, measureHeight)); }

贴上onMeasure的代码后，大家估计是很少见过测量过程这么简单的onMeasure，不要介意，有兴趣的同僚们可以细化一下这个测量过程，对不同的测量模式分别进行处理和测量，让控件适配效果更好更完善！

onMeasure方法中，分别获取期望的宽度和高度，并取其中较小的尺寸作为该控件的宽和高。

3.依次绘制不同的控件组成部分。

因为控件是直接继承自View,所以不需要再处理onLayout方法，这也是自定义View的难度远小于自定义ViewGroup的原因，但继承ViewGroup也并不一定要重写onMeasure。
要实现如图所示的效果，需要分以下步骤依次实现

(1)绘制灰色空心圆环
(2)绘制颜色渐变的圆环
(3)绘制圆环上分割的白色线条
(4)绘制百分比文字等。

绘制过程过，后绘制的内容如果与之前绘制的内容存在交集，则后绘制的内容会覆盖掉之前绘制的内容。

按照上述步骤依次介绍

在绘制过程中，会产生以下成员变量，下文中会用到：

private float circleBorderWidth = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, getResources().getDisplayMetrics()); private float circlePadding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, getResources().getDisplayMetrics()); private float textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 50, getResources().getDisplayMetrics()); private Paint backCirclePaint; private Paint linePaint; private Paint textPaint; private int percent = 0; private int[] gradientColorArray = new int[]{Color.GREEN, Color.parseColor("#fe751a"), Color.parseColor("#13be23"), Color.GREEN}; private Paint gradientCirclePaint;

3.1绘制灰色空心圆环

代码如下：

//1.绘制灰色背景圆环 canvas.drawArc( new RectF(circlePadding * 2, circlePadding * 2, getMeasuredWidth() - circlePadding * 2, getMeasuredHeight() - circlePadding * 2), -90, 360, false, backCirclePaint);

其中，-90为绘制圆弧的起始角度，360是圆弧绘制的角度，即sweepAngle.

3.2绘制颜色渐变的圆环

//2.绘制颜色渐变圆环 LinearGradient linearGradient = new LinearGradient(circlePadding, circlePadding, getMeasuredWidth() - circlePadding, getMeasuredHeight() - circlePadding, gradientColorArray, null, Shader.TileMode.MIRROR); gradientCirclePaint.setShader(linearGradient); gradientCirclePaint.setShadowLayer(10, 10, 10, Color.RED); canvas.drawArc( new RectF(circlePadding * 2, circlePadding * 2, getMeasuredWidth() - circlePadding * 2, getMeasuredHeight() - circlePadding * 2), -90, (float) (percent / 100.0) * 360, false, gradientCirclePaint);

其中，linearGradient是Paint的shadow,是为了圆弧的颜色渐变效果的而需要设置的，日常开发中应用频率不高，但的确是可以实现非常理想的颜色渐变效果。

3.3绘制圆环上分割的白色线条

绘制圆弧上的白色线条时，需要进行一些简单的运算，比如线条的起始坐标startX,startY和线条的终止坐标stopX,stopY等，利用简单的三角函数还是很容易去计算出来的。
效果中，将圆弧使用白色线条平分成100分，每一个的阶级为1，可以满足int类型的百分比与效果图比例的一致。

//半径float radius = (getMeasuredWidth() - circlePadding * 3) / 2; //X轴中点坐标 int centerX = getMeasuredWidth() / 2; //3.绘制100份线段，切分空心圆弧 for (float i = 0; i < 360; i += 3.6) { double rad = i * Math.PI / 180; float startX = (float) (centerX + (radius - circleBorderWidth) * Math.sin(rad)); float startY = (float) (centerX + (radius - circleBorderWidth) * Math.cos(rad)); float stopX = (float) (centerX + radius * Math.sin(rad) + 1); float stopY = (float) (centerX + radius * Math.cos(rad) + 1); canvas.drawLine(startX, startY, stopX, stopY, linePaint); }

3.4绘制百分比文字等

最后绘制百分比文字。
绘制文字时，为了保持文字的中心点和圆弧的原点一致，需要先测量得到要显示文字的宽度和高度，然后再进行一些简单的运算，原理不再赘述，相信大家数学一定都比我好。

//4.绘制文字float textWidth = textPaint.measureText(percent + "%");int textHeight = (int) (Math.ceil(textPaint.getFontMetrics().descent - textPaint.getFontMetrics().ascent) + 2); canvas.drawText(percent + "%", centerX - textWidth / 2, centerX + textHeight / 4, textPaint);

最后，暴漏一个公共的方法供改变显示的百分比，代码如下：

/** * 设置百分比 * * @param percent */ public void setPercent(int percent) { if (percent < 0) { percent = 0; } else if (percent > 100) { percent = 100; } this.percent = percent; invalidate(); }

至此，所有绘制过程简述完毕，130行代码就能实现很炫酷的效果有木有？

最后，贴上项目完整代码，供懒得看实现过程的同僚们使用，O(∩_∩)O哈哈~

package com.example.myview;import android.content.Context;import android.graphics.*;import android.util.AttributeSet;import android.util.TypedValue;import android.view.View;/** * Created by WangChunLei on 2016.1.16 * e-mail:wcl_android@163.com */public class GradientProgressBar extends View { private float circleBorderWidth = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, getResources().getDisplayMetrics()); private float circlePadding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, getResources().getDisplayMetrics()); private float textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 50, getResources().getDisplayMetrics()); private Paint backCirclePaint; private Paint linePaint; private Paint textPaint; private int percent = 0; private int[] gradientColorArray = new int[]{Color.GREEN, Color.parseColor("#fe751a"), Color.parseColor("#13be23"), Color.GREEN}; private Paint gradientCirclePaint; public GradientProgressBar(Context context) { super(context); init(); } public GradientProgressBar(Context context, AttributeSet attrs) { super(context, attrs); init(); } public GradientProgressBar(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(); } private void init() { backCirclePaint = new Paint(); backCirclePaint.setStyle(Paint.Style.STROKE); backCirclePaint.setAntiAlias(true); backCirclePaint.setColor(Color.LTGRAY); backCirclePaint.setStrokeWidth(circleBorderWidth);// backCirclePaint.setMaskFilter(new BlurMaskFilter(20, BlurMaskFilter.Blur.OUTER)); gradientCirclePaint = new Paint(); gradientCirclePaint.setStyle(Paint.Style.STROKE); gradientCirclePaint.setAntiAlias(true); gradientCirclePaint.setColor(Color.LTGRAY); gradientCirclePaint.setStrokeWidth(circleBorderWidth); linePaint = new Paint(); linePaint.setColor(Color.WHITE); linePaint.setStrokeWidth(5); textPaint = new Paint(); textPaint.setAntiAlias(true); textPaint.setTextSize(textSize); textPaint.setColor(Color.BLACK); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int measureWidth = MeasureSpec.getSize(widthMeasureSpec); int measureHeight = MeasureSpec.getSize(heightMeasureSpec); setMeasuredDimension(Math.min(measureWidth, measureHeight), Math.min(measureWidth, measureHeight)); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); //1.绘制灰色背景圆环 canvas.drawArc( new RectF(circlePadding * 2, circlePadding * 2, getMeasuredWidth() - circlePadding * 2, getMeasuredHeight() - circlePadding * 2), -90, 360, false, backCirclePaint); //2.绘制颜色渐变圆环 LinearGradient linearGradient = new LinearGradient(circlePadding, circlePadding, getMeasuredWidth() - circlePadding, getMeasuredHeight() - circlePadding, gradientColorArray, null, Shader.TileMode.MIRROR); gradientCirclePaint.setShader(linearGradient); gradientCirclePaint.setShadowLayer(10, 10, 10, Color.RED); canvas.drawArc( new RectF(circlePadding * 2, circlePadding * 2, getMeasuredWidth() - circlePadding * 2, getMeasuredHeight() - circlePadding * 2), -90, (float) (percent / 100.0) * 360, false, gradientCirclePaint); //半径 float radius = (getMeasuredWidth() - circlePadding * 3) / 2; //X轴中点坐标 int centerX = getMeasuredWidth() / 2; //3.绘制100份线段，切分空心圆弧 for (float i = 0; i < 360; i += 3.6) { double rad = i * Math.PI / 180; float startX = (float) (centerX + (radius - circleBorderWidth) * Math.sin(rad)); float startY = (float) (centerX + (radius - circleBorderWidth) * Math.cos(rad)); float stopX = (float) (centerX + radius * Math.sin(rad) + 1); float stopY = (float) (centerX + radius * Math.cos(rad) + 1); canvas.drawLine(startX, startY, stopX, stopY, linePaint); } //4.绘制文字 float textWidth = textPaint.measureText(percent + "%"); int textHeight = (int) (Math.ceil(textPaint.getFontMetrics().descent - textPaint.getFontMetrics().ascent) + 2); canvas.drawText(percent + "%", centerX - textWidth / 2, centerX + textHeight / 4, textPaint); } /** * 设置百分比 * * @param percent */ public void setPercent(int percent) { if (percent < 0) { percent = 0; } else if (percent > 100) { percent = 100; } this.percent = percent; invalidate(); }}

最后，贴上自定义控件代码(自定义控件、Activity，布局文件)下载地址： Android圆形进度CircleProgressBar

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。