Android实现渐变圆环、圆形进度条效果

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。

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自由互联。