Android 渐变圆环，圆形进度条效果实现

2021-11-20 10:59:30

最近做了一个功能，里面涉及到了渐变圆形的需求。就是一个颜色可以渐变的圆环，最后实现的效果如下图：

左图是带渐变效果，右图是不带渐变效果。原理还是绘图，Canvas可以绘制的对象有：弧线(arcs)、填充颜色(argb和color)、

Bitmap、圆(circle和oval)、点(point)、线(line)、矩形(Rect)、图片(Picture)、圆角矩形 (RoundRect)、文本(text)、

顶点(Vertices)、路径(path)。通过组合这些对象我们可以画出一些简单有趣的界面出来，但是光有这些功能还是不够的，

如果我要画一个仪表盘(数字围绕显示在一个圆圈中)呢？幸好Android还提供了一些对Canvas位置转换的方法：rorate、scale、

translate、skew(扭曲)等，而且它允许你通过获得它的转换矩阵对象(getMatrix方法，不知道什么是转换矩阵？)

直接操作它。这些操作就像是虽然你的笔还是原来的地方画，但是画纸旋转或者移动了，所以你画的东西的方位就产生变化。

为了方便一些转换操作，Canvas 还提供了保存和回滚属性的方法(save和restore)，比如你可以先保存目前画纸的位置(save)，

然后旋转90度，向下移动100像素后画一些图形，画完后调用restore方法返回到刚才保存的位置。

话不多说，上代码

核心类：

自定义控件 CircleProgressBar

package com.jky.mobile_xmxt.view;
 
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;
 
import com.jky.mobile_xmxt.R;
 
import java.text.DecimalFormat;
 
/**
 * 圆盘计步图表
 */
public class CircleProgressBar extends View {
 
    private RectF mWheelRect = new RectF();
    private Paint mDefaultWheelPaint;
    private Paint mFinishWheelPaint;
    private Paint mCenterWheelPaint;
    private Paint mTitlePaint, mStepPaint, mTargetPaint;
    private float mCircleStrokeWidth;
    private float mSweepAnglePer;
    private float mPercent;
    private int mStepNum, mCurrStepNum;
    private float pressExtraStrokeWidth;
    private BarAnimation mAnim;
    private int mMaxStepNum;// 默认最大步数
    private float mTitleY, mStepY, mTargetY;
    private DecimalFormat mDecimalFormat = new DecimalFormat("#.0");// 格式为保留小数点后一位
    public static String GOAL_STEP;
    public static String PERCENT;
 
    public CircleProgressBar(Context context) {
        super(context);
        init(null, 0);
    }
 
    public CircleProgressBar(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs, 0);
    }
 
    public CircleProgressBar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(attrs, defStyle);
    }
 
    private void init(AttributeSet attrs, int defStyle) {
 
        mFinishWheelPaint = new Paint();
        mFinishWheelPaint.setColor(Color.rgb(100, 113, 205));
        mFinishWheelPaint.setStyle(Paint.Style.STROKE);// 空心
        mFinishWheelPaint.setStrokeCap(Paint.Cap.ROUND);// 圆角画笔
        mFinishWheelPaint.setAntiAlias(true);// 去锯齿
 
        mCenterWheelPaint = new Paint();
        mCenterWheelPaint.setColor(Color.rgb(243, 243, 243));
        mCenterWheelPaint.setStyle(Paint.Style.STROKE);
        mCenterWheelPaint.setStrokeCap(Paint.Cap.ROUND);
        mCenterWheelPaint.setAntiAlias(true);
 
        mDefaultWheelPaint = new Paint();
        mDefaultWheelPaint.setColor(Color.rgb(127, 127, 127));
        mDefaultWheelPaint.setStyle(Paint.Style.STROKE);
        mDefaultWheelPaint.setStrokeCap(Paint.Cap.ROUND);
        mDefaultWheelPaint.setAntiAlias(true);
 
        mTitlePaint = new Paint();
        mTitlePaint.setAntiAlias(true);
        mTitlePaint.setColor(Color.WHITE);
 
        mStepPaint = new Paint();
        mStepPaint.setAntiAlias(true);
        mStepPaint.setColor(Color.WHITE);
 
        mTargetPaint = new Paint();
        mTargetPaint.setAntiAlias(true);
        mTargetPaint.setColor(Color.WHITE);
        mAnim = new BarAnimation();
    }
 
    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawArc(mWheelRect, 0, 359, false, mDefaultWheelPaint);
        canvas.drawArc(mWheelRect, 0, 359, false, mCenterWheelPaint);
        canvas.drawArc(mWheelRect, 90, mSweepAnglePer, false, mFinishWheelPaint);
//      canvas.drawText("步数", mWheelRect.centerX() - (mTitlePaint.measureText("步数") / 2), mTitleY,
//              mTitlePaint);
        canvas.drawText(mCurrStepNum + "",
                mWheelRect.centerX() - (mStepPaint.measureText(String.valueOf(mCurrStepNum)) / 2), mStepY,
                mStepPaint);
        String description = "";
        float percent = getPercent();
        if(percent > 0.5){
            description ="严重污染";
        }else if(percent<0.5){
            description ="中等污染";
        }else{
            description ="普通污染";
        }
 
        canvas.drawText(description , mWheelRect.centerX() -
                (mTargetPaint.measureText(description) / 2), mTargetY, mTargetPaint);
        SweepGradient sweepGradient = new SweepGradient(mWheelRect.centerX(), mWheelRect.centerY(),
                new int[]{getResources().getColor(R.color.color_environment_severe), getResources().getColor(R.color.color_environment_serious),
                        getResources().getColor(R.color.color_environment_excellent),
                        getResources().getColor(R.color.color_environment_good), getResources().getColor(R.color.color_environment_mild),
                        getResources().getColor(R.color.color_environment_moderate)}, null);
        mFinishWheelPaint.setShader(sweepGradient);
    }
 
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);
        int width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        int min = Math.min(width, height);// 获取View最短边的长度
        setMeasuredDimension(min, min);// 强制改View为以最短边为长度的正方形
        mCircleStrokeWidth = getTextScale(15, min);// 圆弧的宽度
        pressExtraStrokeWidth = getTextScale(10, min);// 圆弧离矩形的距离
        mWheelRect.set(mCircleStrokeWidth + pressExtraStrokeWidth, mCircleStrokeWidth + pressExtraStrokeWidth,
                min - mCircleStrokeWidth - pressExtraStrokeWidth, min - mCircleStrokeWidth - pressExtraStrokeWidth);// 设置矩形
        mTitlePaint.setTextSize(getTextScale(60, min));
        mStepPaint.setTextSize(getTextScale(120, min));
        mTargetPaint.setTextSize(getTextScale(40, min));
        mTitleY = getTextScale(170, min);
        mStepY = getTextScale(300, min);
        mTargetY = getTextScale(380, min);
        mFinishWheelPaint.setStrokeWidth(mCircleStrokeWidth);
        mCenterWheelPaint.setStrokeWidth(mCircleStrokeWidth);
        mDefaultWheelPaint.setStrokeWidth(mCircleStrokeWidth - getTextScale(2, min));
        mDefaultWheelPaint.setShadowLayer(getTextScale(10, min), 0, 0, Color.rgb(127, 127, 127));// 设置阴影
    }
 
    /**
     * 进度条动画
     *
     * @author Administrator
     */
    public class BarAnimation extends Animation {
 
        /**
         * 每次系统调用这个方法时， 改变mSweepAnglePer，mPercent，stepnumbernow的值，
         * 然后调用postInvalidate()不停的绘制view。
         */
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
//          if (interpolatedTime < 1.0f) {
//              mPercent = Float.parseFloat(mDecimalFormat.format(interpolatedTime * mStepNum * 100f / mMaxStepNum));// 将浮点值四舍五入保留一位小数
//              mSweepAnglePer = interpolatedTime * mStepNum * 360 / mMaxStepNum;
//              mCurrStepNum = (int) (interpolatedTime * mStepNum);
//          } else {
            mPercent = Float.parseFloat(mDecimalFormat.format(mStepNum * 100f / mMaxStepNum));// 将浮点值四舍五入保留一位小数
            if (mPercent > 100.0f) {
                mPercent = 100.0f;
            }
            PERCENT = String.valueOf(mPercent);
            mSweepAnglePer = mStepNum * 360 / mMaxStepNum;
            mCurrStepNum = mStepNum;
//          }
 
            requestLayout();
        }
    }
 
    public float getPercent() {
        return mPercent;
    }
 
    /**
     * 根据控件的大小改变绝对位置的比例
     *
     * @param n
     * @param m
     * @return
     */
    public float getTextScale(float n, float m) {
        return n / 500 * m;
    }
 
    /**
     * 更新步数和设置一圈动画时间
     *
     * @param stepCount
     * @param time
     */
    public void update(int stepCount, int time) {
        this.mStepNum = stepCount;
        mAnim.setDuration(time);
        // setAnimationTime(time);
        this.startAnimation(mAnim);
    }
 
    /**
     * @param stepNum
     */
    public void setMaxStepNum(int stepNum) {
        mMaxStepNum = stepNum;
        GOAL_STEP = String.valueOf(mMaxStepNum);
    }
 
    public void setColor(int color) {
        mFinishWheelPaint.setColor(color);
        mStepPaint.setColor(color);
    }
 
    /**
     * 设置动画时间
     *
     * @param time
     */
    public void setAnimationTime(int time) {
        mAnim.setDuration(time * mStepNum / mMaxStepNum);// 按照比例设置动画执行时间
    }
 
}

xml引用

     <com.jky.mobile_xmxt.view.CircleProgressBar
                    android:id="@+id/color_progress_view"
                    android:layout_width="match_parent"
                    android:layout_height="0dp"
                    android:layout_weight="6"
                    />

Activity调用方法

   color_progress_view = (CircleProgressBar)view.findViewById(R.id.color_progress_view);
        color_progress_view.setMaxStepNum(500);
        color_progress_view.update(470,1000);

由于和调用其他控件方法类似，姑且省去了很多其他业务逻辑代码，代码不是特别复杂，修改起来也很方便（修改颜色，总量及比例等），所以只粘贴核心相关的代码，希望可以帮助到大家。

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