Android 自定义View实现环形带刻度颜色渐变的进度条

上次写了一篇Android 自定义View实现环形带刻度的进度条，这篇文章就简单了，只是在原来的基础上加一个颜色渐变。
按照惯例，我们先来看看效果图

一、概述
1、相比于上篇文章，这里我们的颜色渐变主要是用到Shader类，通过Paint.setShader(shader)方法为画笔Paint设置shader，这样就可以绘制出多彩的图形。那么Shader是什么呢？
Shader类是Android在图形变换中非常重要的一个类。Shader是着色器的意思，其作用是来给图像着色。
它有五个子类，每个子类都实现了Shader。

 - BitmapShader
 - ComposeShader
 - LinearGradient
 - RadialGradient
 - SweepGradient

2、LinearGradient
在这里我们用LinearGradient创建线性渐变效果，其有两个构造函数：

LinearGradient(float x0, float y0, float x1, float y1, int color0, int color1, Shader.TileMode tile)

LinearGradient(float x0, float y0, float x1, float y1, int[] colors, float[] positions, Shader.TileMode tile)

我们重点说一下第一个构造函数，在此基础上理解第二个构造函数就很简单了。

LinearGradient是用来创建线性渐变效果的，它是沿着某条直线的方向渐变的，坐标(x0,y0)就是这条渐变直线的起点，坐标(x1,y1)就是这条渐变直线的终点。需要说明的是，坐标(x0,y0)和坐标(x1,y1)都是Canvas绘图坐标系中的坐标。color0和color1分别表示了渐变的起始颜色和终止颜色。LinearGradient支持TileMode，有以下三个取值：CLAMP 、REPEAT 和 MIRROR。
我们主要是添加这段代码，如下所示：

 if (useGradient) {
            LinearGradient gradient = new LinearGradient(0, 0, w, h, foreEndColcor, foreStartColor, Shader.TileMode.CLAMP);
            mArcPaint.setShader(gradient);
        } else {
            mArcPaint.setColor(mArcColor);
        }

二、按照流程我们就开始来看看代码啦
1、自定义View的属性，首先在res/values/ 下建立一个attrs.xml ， 在里面定义我们的需要用到的属性以及声明相对应属性的取值类型，这里面我们主要是增加了一个起始颜色和结束颜色：

<resources>
    
    <attr name="antiAlias" format="boolean" />
    
    <attr name="startAngle" format="float" />
    
    <attr name="sweepAngle" format="float" />
    
    <attr name="animTime" format="integer" />
    
    <attr name="maxValue" format="float" />
    <attr name="value" format="float" />
    
    <attr name="unit" format="string|reference" />
    <attr name="unitSize" format="dimension" />
    <attr name="unitColor" format="color|reference" />
    
    <attr name="hint" format="string|reference" />
    <attr name="hintSize" format="dimension" />
    <attr name="hintColor" format="color|reference" />
    
    <attr name="precision" format="integer" />
    <attr name="valueSize" format="dimension" />
    <attr name="valueColor" format="color|reference" />
    
    <attr name="bgArcColor" format="color|reference" />
    
    <attr name="arcWidth" format="dimension" />
    
    <attr name="arcColors" format="color|reference" />
    
    <attr name="textOffsetPercentInRadius" format="float" />
    
    <attr name="bgArcWidth" format="dimension" />
    
    <attr name="dottedLineCount" format="integer" />
    
    <attr name="lineDistance" format="integer" />
    
    <attr name="dottedLineWidth" format="dimension" />
    
    <attr name="foreStartColor" format="color" />
    
    <attr name="foreEndColor" format="color" />

    <declare-styleable name="CircleProgressBar">
        <attr name="antiAlias" />
        <attr name="startAngle" />
        <attr name="sweepAngle" />
        <attr name="animTime" />
        <attr name="maxValue" />
        <attr name="value" />
        <attr name="unit" />
        <attr name="unitSize" />
        <attr name="unitColor" />
        <attr name="hint" />
        <attr name="hintSize" />
        <attr name="hintColor" />
        <attr name="precision" />
        <attr name="valueSize" />
        <attr name="valueColor" />
        <attr name="bgArcColor" />
        <attr name="arcWidth" />
        <attr name="arcColors" />
        <attr name="textOffsetPercentInRadius" />
        <attr name="bgArcWidth" />
        <attr name="dottedLineCount" />
        <attr name="lineDistance" />
        <attr name="dottedLineWidth" />
        <attr name="foreStartColor" />
        <attr name="foreEndColor" />

    declare-styleable>

resources>

2、然后在XML布局中声明我们的自定义View，并定义了起始颜色和结束颜色

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#29292F">

    <per.lijuan.circleprogress.CircleProgress
        android:id="@+id/circle_progress"
        android:layout_width="250dp"
        android:layout_height="250dp"
        android:layout_gravity="center_horizontal"
        app:antiAlias="true"
        app:arcWidth="15dp"
        app:dottedLineWidth="12dp"
        app:bgArcColor="@android:color/darker_gray"
        app:foreStartColor="#FE6615"
        app:foreEndColor="#F4F200"
        app:bgArcWidth="2dp"
        app:hintSize="15dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.498"
        app:maxValue="100"
        app:startAngle="135"
        app:sweepAngle="270"
        app:textOffsetPercentInRadius="0.5"
        app:unit="目标100KM"
        app:unitColor="@android:color/darker_gray"
        app:unitSize="15dp"
        app:value="75"
        app:valueColor="#FFCC1E"
        app:valueSize="80dp" />

android.support.constraint.ConstraintLayout>

一定要引入xmlns:app=”http://schemas.android.com/apk/res-auto”，Android Studio中我们可以使用res-atuo命名空间,就不用添加自定义View全类名。

3、在View的构造方法中，获得我们的自定义的样式并绘制环形刻度进度条

package per.lijuan.circleprogress;

import android.animation.ValueAnimator;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.RectF;
import android.graphics.Shader;
import android.graphics.Typeface;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

public class CircleProgress extends View {

    private static final String TAG = CircleProgress.class.getSimpleName();

    private Context mContext;
    //默认大小
    private int mDefaultSize;
    //是否开启抗锯齿
    private boolean antiAlias;
    //绘制提示
    private TextPaint mHintPaint;
    private CharSequence mHint;
    private int mHintColor;
    private float mHintSize;
    private float mHintOffset;

    //绘制单位
    private TextPaint mUnitPaint;
    private CharSequence mUnit;
    private int mUnitColor;
    private float mUnitSize;
    private float mUnitOffset;

    //绘制数值
    private TextPaint mValuePaint;
    private float mValue;
    private float mMaxValue;
    private float mValueOffset;
    private int mPrecision;
    private String mPrecisionFormat;
    private int mValueColor;
    private float mValueSize;

    //绘制圆弧
    private Paint mArcPaint;
    private float mArcWidth;
    private float mStartAngle, mSweepAngle;
    private RectF mRectF;
    //当前进度，[0.0f,1.0f]
    private float mPercent;
    //动画时间
    private long mAnimTime;
    //属性动画
    private ValueAnimator mAnimator;

    //绘制背景圆弧
    private Paint mBgArcPaint;
    private int mBgArcColor;
    private int mArcColor;
    private float mBgArcWidth;

    //圆心坐标，半径
    private Point mCenterPoint;
    private float mRadius;
    private float mTextOffsetPercentInRadius;

    private int mArcCenterX;
    // 内部虚线的外部半径
    private float mExternalDottedLineRadius;
    // 内部虚线的内部半径
    private float mInsideDottedLineRadius;

    // 线条数
    private int mDottedLineCount = 100;
    // 圆弧跟虚线之间的距离
    private int mLineDistance = 20;
    // 线条宽度
    private float mDottedLineWidth = 40;
    //是否使用渐变
    protected boolean useGradient=true;
    //前景色起始颜色
    private int foreStartColor;
    //前景色结束颜色
    private int foreEndColcor;
    protected int mWidth;
    protected int mHeight;

    public CircleProgress(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        mContext = context;
        mDefaultSize = dipToPx(mContext, 150);
        mAnimator = new ValueAnimator();
        mRectF = new RectF();
        mCenterPoint = new Point();
        initAttrs(attrs);
        initPaint();
        setValue(mValue);
    }

    private void initAttrs(AttributeSet attrs) {
        TypedArray typedArray = mContext.obtainStyledAttributes(attrs, R.styleable.CircleProgressBar);

        antiAlias = typedArray.getBoolean(R.styleable.CircleProgressBar_antiAlias, true);

        mHint = typedArray.getString(R.styleable.CircleProgressBar_hint);
        mHintColor = typedArray.getColor(R.styleable.CircleProgressBar_hintColor, Color.BLACK);
        mHintSize = typedArray.getDimension(R.styleable.CircleProgressBar_hintSize, 15);

        mValue = typedArray.getFloat(R.styleable.CircleProgressBar_value, 50);
        mMaxValue = typedArray.getFloat(R.styleable.CircleProgressBar_maxValue, 50);
        //内容数值精度格式
        mPrecision = typedArray.getInt(R.styleable.CircleProgressBar_precision, 0);
        mPrecisionFormat = getPrecisionFormat(mPrecision);
        mValueColor = typedArray.getColor(R.styleable.CircleProgressBar_valueColor, Color.BLACK);
        mValueSize = typedArray.getDimension(R.styleable.CircleProgressBar_valueSize, 15);

        mUnit = typedArray.getString(R.styleable.CircleProgressBar_unit);
        mUnitColor = typedArray.getColor(R.styleable.CircleProgressBar_unitColor, Color.BLACK);
        mUnitSize = typedArray.getDimension(R.styleable.CircleProgressBar_unitSize, 30);

        mArcWidth = typedArray.getDimension(R.styleable.CircleProgressBar_arcWidth, 15);
        mStartAngle = typedArray.getFloat(R.styleable.CircleProgressBar_startAngle, 270);
        mSweepAngle = typedArray.getFloat(R.styleable.CircleProgressBar_sweepAngle, 360);

        mBgArcColor = typedArray.getColor(R.styleable.CircleProgressBar_bgArcColor, Color.WHITE);
        mArcColor = typedArray.getColor(R.styleable.CircleProgressBar_arcColors, Color.RED);
        mBgArcWidth = typedArray.getDimension(R.styleable.CircleProgressBar_bgArcWidth, 15);
        mTextOffsetPercentInRadius = typedArray.getFloat(R.styleable.CircleProgressBar_textOffsetPercentInRadius, 0.33f);
        mAnimTime = typedArray.getInt(R.styleable.CircleProgressBar_animTime, 1000);
        mDottedLineCount = typedArray.getInteger(R.styleable.CircleProgressBar_dottedLineCount, mDottedLineCount);
        mLineDistance = typedArray.getInteger(R.styleable.CircleProgressBar_lineDistance, mLineDistance);
        mDottedLineWidth = typedArray.getDimension(R.styleable.CircleProgressBar_dottedLineWidth, mDottedLineWidth);
        foreStartColor = typedArray.getColor(R.styleable.CircleProgressBar_foreStartColor, Color.BLUE);
        foreEndColcor = typedArray.getColor(R.styleable.CircleProgressBar_foreEndColor, Color.BLUE);
        typedArray.recycle();
    }

    private void initPaint() {
        mHintPaint = new TextPaint();
        // 设置抗锯齿,会消耗较大资源，绘制图形速度会变慢。
        mHintPaint.setAntiAlias(antiAlias);
        // 设置绘制文字大小
        mHintPaint.setTextSize(mHintSize);
        // 设置画笔颜色
        mHintPaint.setColor(mHintColor);
        // 从中间向两边绘制，不需要再次计算文字
        mHintPaint.setTextAlign(Paint.Align.CENTER);

        mValuePaint = new TextPaint();
        mValuePaint.setAntiAlias(antiAlias);
        mValuePaint.setTextSize(mValueSize);
        mValuePaint.setColor(mValueColor);
        // 设置Typeface对象，即字体风格，包括粗体，斜体以及衬线体，非衬线体等
        mValuePaint.setTypeface(Typeface.DEFAULT_BOLD);
        mValuePaint.setTextAlign(Paint.Align.CENTER);

        mUnitPaint = new TextPaint();
        mUnitPaint.setAntiAlias(antiAlias);
        mUnitPaint.setTextSize(mUnitSize);
        mUnitPaint.setColor(mUnitColor);
        mUnitPaint.setTextAlign(Paint.Align.CENTER);

        mArcPaint = new Paint();
        mArcPaint.setAntiAlias(antiAlias);
        // 设置画笔的样式，为FILL，FILL_OR_STROKE，或STROKE
        mArcPaint.setStyle(Paint.Style.STROKE);
        // 设置画笔粗细
        mArcPaint.setStrokeWidth(mArcWidth);
        // 当画笔样式为STROKE或FILL_OR_STROKE时，设置笔刷的图形样式，如圆形样式
        // Cap.ROUND(圆形样式)或Cap.SQUARE(方形样式)
        mArcPaint.setStrokeCap(Paint.Cap.ROUND);

        mBgArcPaint = new Paint();
        mBgArcPaint.setAntiAlias(antiAlias);
        mBgArcPaint.setColor(mBgArcColor);
        mBgArcPaint.setStyle(Paint.Style.STROKE);
        mBgArcPaint.setStrokeWidth(mBgArcWidth);
        mBgArcPaint.setStrokeCap(Paint.Cap.ROUND);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(measureView(widthMeasureSpec, mDefaultSize),
                measureView(heightMeasureSpec, mDefaultSize));
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mArcCenterX = (int) (w / 2.f);
        Log.d(TAG, "onSizeChanged: w = " + w + "; h = " + h + "; oldw = " + oldw + "; oldh = " + oldh);
        //求圆弧和背景圆弧的最大宽度
        float maxArcWidth = Math.max(mArcWidth, mBgArcWidth);
        //求最小值作为实际值
        int minSize = Math.min(w - getPaddingLeft() - getPaddingRight() - 2 * (int) maxArcWidth,
                h - getPaddingTop() - getPaddingBottom() - 2 * (int) maxArcWidth);
        //减去圆弧的宽度，否则会造成部分圆弧绘制在外围
        mRadius = minSize / 2;
        //获取圆的相关参数
        mCenterPoint.x = w / 2;
        mCenterPoint.y = h / 2;
        //绘制圆弧的边界
        mRectF.left = mCenterPoint.x - mRadius - maxArcWidth / 2;
        mRectF.top = mCenterPoint.y - mRadius - maxArcWidth / 2;
        mRectF.right = mCenterPoint.x + mRadius + maxArcWidth / 2;
        mRectF.bottom = mCenterPoint.y + mRadius + maxArcWidth / 2;
        //计算文字绘制时的 baseline
        //由于文字的baseline、descent、ascent等属性只与textSize和typeface有关，所以此时可以直接计算
        //若value、hint、unit由同一个画笔绘制或者需要动态设置文字的大小，则需要在每次更新后再次计算
        mValueOffset = mCenterPoint.y + getBaselineOffsetFromY(mValuePaint);
        mHintOffset = mCenterPoint.y - mRadius * mTextOffsetPercentInRadius + getBaselineOffsetFromY(mHintPaint);
        mUnitOffset = mCenterPoint.y + mRadius * mTextOffsetPercentInRadius + getBaselineOffsetFromY(mUnitPaint);

        if (useGradient) {
            LinearGradient gradient = new LinearGradient(0, 0, w, h, foreEndColcor, foreStartColor, Shader.TileMode.CLAMP);
            mArcPaint.setShader(gradient);
        } else {
            mArcPaint.setColor(mArcColor);
        }

        Log.d(TAG, "onSizeChanged: 控件大小 = " + "(" + w + ", " + h + ")"
                + "圆心坐标 = " + mCenterPoint.toString()
                + ";圆半径 = " + mRadius
                + ";圆的外接矩形 = " + mRectF.toString());

        // 虚线的外部半径
        mExternalDottedLineRadius = (int) (mRectF.width() / 2)+mLineDistance;
        // 虚线的内部半径
        mInsideDottedLineRadius = mExternalDottedLineRadius - mDottedLineWidth;
    }

    private float getBaselineOffsetFromY(Paint paint) {
        Paint.FontMetrics fontMetrics = paint.getFontMetrics();
        return ((Math.abs(fontMetrics.ascent) - fontMetrics.descent))/ 2;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawText(canvas);
        drawArc(canvas);
    }

    /**
     * 绘制内容文字
     *
     * @param canvas
     */
    private void drawText(Canvas canvas) {
        canvas.drawText(String.format(mPrecisionFormat, mValue), mCenterPoint.x, mValueOffset, mValuePaint);

        if (mHint != null) {
            canvas.drawText(mHint.toString(), mCenterPoint.x, mHintOffset, mHintPaint);
        }

        if (mUnit != null) {
            canvas.drawText(mUnit.toString(), mCenterPoint.x, mUnitOffset, mUnitPaint);
        }
    }

    private void drawArc(Canvas canvas) {
        // 绘制背景圆弧
        // 从进度圆弧结束的地方开始重新绘制，优化性能
        canvas.save();

        // 360 * Math.PI / 180
        float evenryDegrees = (float) (2.0f * Math.PI / mDottedLineCount);
        float startDegress = (float) (135 * Math.PI / 180);
        float endDegress = (float) (225 * Math.PI / 180);
        for (int i = 0; i < mDottedLineCount; i++) {
            float degrees = i * evenryDegrees;
            // 过滤底部90度的弧长
            if (degrees > startDegress && degrees < endDegress) {
                continue;
            }
            float startX = mArcCenterX + (float) Math.sin(degrees) * mInsideDottedLineRadius;
            float startY = mArcCenterX - (float) Math.cos(degrees) * mInsideDottedLineRadius;

            float stopX = mArcCenterX + (float) Math.sin(degrees) * mExternalDottedLineRadius;
            float stopY = mArcCenterX - (float) Math.cos(degrees) * mExternalDottedLineRadius;

            canvas.drawLine(startX, startY, stopX, stopY, mBgArcPaint);
        }

        canvas.rotate(mStartAngle, mCenterPoint.x, mCenterPoint.y);

        // 第一个参数 oval 为 RectF 类型，即圆弧显示区域
        // startAngle 和 sweepAngle  均为 float 类型，分别表示圆弧起始角度和圆弧度数
        // 3点钟方向为0度，顺时针递增
        // 如果 startAngle < 0 或者 > 360,则相当于 startAngle % 360
        // useCenter:如果为True时，在绘制圆弧时将圆心包括在内，通常用来绘制扇形
        float currentAngle = mSweepAngle * mPercent;
        canvas.drawArc(mRectF, 2, currentAngle, false, mArcPaint);
        canvas.restore();
    }

    public boolean isAntiAlias() {
        return antiAlias;
    }

    public CharSequence getHint() {
        return mHint;
    }

    public void setHint(CharSequence hint) {
        mHint = hint;
    }

    public CharSequence getUnit() {
        return mUnit;
    }

    public void setUnit(CharSequence unit) {
        mUnit = unit;
    }

    public float getValue() {
        return mValue;
    }

    /**
     * 设置当前值
     *
     * @param value
     */
    public void setValue(float value) {
        if (value > mMaxValue) {
            value = mMaxValue;
        }
        float start = mPercent;
        float end = value / mMaxValue;
        startAnimator(start, end, mAnimTime);
    }

    private void startAnimator(float start, float end, long animTime) {
        mAnimator = ValueAnimator.ofFloat(start, end);
        mAnimator.setDuration(animTime);
        mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                mPercent = (float) animation.getAnimatedValue();
                mValue = mPercent * mMaxValue;
                if (BuildConfig.DEBUG) {
                    Log.d(TAG, "onAnimationUpdate: percent = " + mPercent
                            + ";currentAngle = " + (mSweepAngle * mPercent)
                            + ";value = " + mValue);
                }
                invalidate();
            }
        });
        mAnimator.start();
    }

    /**
     * 获取最大值
     *
     * @return
     */
    public float getMaxValue() {
        return mMaxValue;
    }

    /**
     * 设置最大值
     *
     * @param maxValue
     */
    public void setMaxValue(float maxValue) {
        mMaxValue = maxValue;
    }

    /**
     * 获取精度
     *
     * @return
     */
    public int getPrecision() {
        return mPrecision;
    }

    public void setPrecision(int precision) {
        mPrecision = precision;
        mPrecisionFormat = getPrecisionFormat(precision);
    }

    public long getAnimTime() {
        return mAnimTime;
    }

    public void setAnimTime(long animTime) {
        mAnimTime = animTime;
    }

    /**
     * 重置
     */
    public void reset() {
        startAnimator(mPercent, 0.0f, 1000L);
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        //释放资源
    }

    /**
     * 测量 View
     *
     * @param measureSpec
     * @param defaultSize View 的默认大小
     * @return
     */
    private static int measureView(int measureSpec, int defaultSize) {
        int result = defaultSize;
        int specMode = View.MeasureSpec.getMode(measureSpec);
        int specSize = View.MeasureSpec.getSize(measureSpec);

        if (specMode == View.MeasureSpec.EXACTLY) {
            result = specSize;
        } else if (specMode == View.MeasureSpec.AT_MOST) {
            result = Math.min(result, specSize);
        }
        return result;
    }

    /**
     * dip 转换成px
     *
     * @param dip
     * @return
     */
    public static int dipToPx(Context context, float dip) {
        float density = context.getResources().getDisplayMetrics().density;
        return (int) (dip * density + 0.5f * (dip >= 0 ? 1 : -1));
    }

    /**
     * 获取数值精度格式化字符串
     *
     * @param precision
     * @return
     */
    public static String getPrecisionFormat(int precision) {
        return "%." + precision + "f";
    }
}

4、在MainActivity中，点击按钮随机改变当前值

package per.lijuan.circleprogress;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import java.util.Random;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private CircleProgress mCircleProgress;
    private Random mRandom;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mCircleProgress = (CircleProgress) findViewById(R.id.circle_progress);
        mCircleProgress.setOnClickListener(this);
        mRandom = new Random();
    }
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.circle_progress:
                mCircleProgress.setValue(mRandom.nextFloat() * mCircleProgress.getMaxValue());
                break;
        }
    }
}

好了，本篇文章就这样了，存在不足的地方还望指导，感谢^_^

源码下载