首先来看看效果图：

1，SweepGradient(梯度渲染)

public SweepGradient (float cx, float cy, int[] colors, float[] positions)

扫描渲染，就是以某个点位中心旋转一周所形成的效果！参数依次是：

cx：扫描的中心x坐标

cy：扫描的中心y坐标

colors：梯度渐变的颜色数组

positions：指定颜色数组的相对位置

public static final int[] SWEEP_GRADIENT_COLORS = new int[]{Color.GREEN, Color.GREEN, Color.BLUE, Color.RED, Color.RED};mColorShader = new SweepGradient(radius, radius,SWEEP_GRADIENT_COLORS,null);

效果图：

SweepGradient

2，DashPathEffect(Path的线段虚线化)

DashPathEffect(float[] intervals, float phase)

intervals：为虚线的ON和OFF的数组，数组中元素数目需要 >= 2

phase：为绘制时的偏移量

//计算路径的长度PathMeasure pathMeasure = new PathMeasure(mPath, false);float length = pathMeasure.getLength();float step = length / 60;dashPathEffect = new DashPathEffect(new float[]{step / 3, step * 2 / 3}, 0);

效果图：

DashPathEffect

3，下面是全部的代码：

package com.example.yyw.xfermodedemo;import android.animation.ValueAnimator;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.DashPathEffect;import android.graphics.Paint;import android.graphics.Path;import android.graphics.PathMeasure;import android.graphics.RectF;import android.graphics.SweepGradient;import android.util.AttributeSet;import android.view.View;/** * Created by yyw on 2016/10/11. */public class OilTableLine extends View { public static final int[] SWEEP_GRADIENT_COLORS = new int[]{Color.GREEN, Color.GREEN, Color.BLUE, Color.RED, Color.RED}; private int tableWidth = 50; private Paint mPaint; private Path mPath; private RectF mTableRectF; //把路径分成虚线段的 private DashPathEffect dashPathEffect; //给路径上色 private SweepGradient mColorShader; //指针的路径 private Path mPointerPath; private float mCurrentDegree = 60; public OilTableLine(Context context, AttributeSet attrs) { super(context, attrs); mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setDither(true); mPaint.setColor(Color.BLACK); mPath = new Path(); mPointerPath = new Path(); startAnimator(); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); float size = Math.min(w, h) - tableWidth * 2; //油表的位置方框 mTableRectF = new RectF(0, 0, size, size); mPath.reset(); //在油表路径中增加一个从起始弧度 mPath.addArc(mTableRectF, 60, 240); //计算路径的长度 PathMeasure pathMeasure = new PathMeasure(mPath, false); float length = pathMeasure.getLength(); float step = length / 60; dashPathEffect = new DashPathEffect(new float[]{step / 3, step * 2 / 3}, 0); float radius = size / 2; mColorShader = new SweepGradient(radius, radius,SWEEP_GRADIENT_COLORS,null); //设置指针的路径位置 mPointerPath.reset(); mPointerPath.moveTo(radius, radius - 20); mPointerPath.lineTo(radius, radius + 20); mPointerPath.lineTo(radius * 2 - tableWidth, radius); mPointerPath.close(); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); float dx = (getWidth() - mTableRectF.width()) / 2; float dy = (getHeight() - mTableRectF.height()) / 2; //把油表的方框平移到正中间 canvas.translate(dx, dy); canvas.save(); //旋转画布 canvas.rotate(90, mTableRectF.width() / 2, mTableRectF.height() / 2); mPaint.setStyle(Paint.Style.STROKE); mPaint.setStrokeWidth(tableWidth); mPaint.setPathEffect(dashPathEffect); mPaint.setShader(mColorShader); canvas.drawPath(mPath, mPaint); canvas.restore(); //还原画笔 mPaint.setPathEffect(null); mPaint.setShader(null); mPaint.setStyle(Paint.Style.FILL); mPaint.setStrokeWidth(tableWidth / 10); canvas.save(); canvas.rotate(150 + mCurrentDegree, mTableRectF.width() / 2, mTableRectF.height() / 2); canvas.drawPath(mPointerPath, mPaint); canvas.restore(); } public void startAnimator() { ValueAnimator animator = ValueAnimator.ofFloat(0, 240); animator.setDuration(40000); animator.setRepeatCount(ValueAnimator.INFINITE); animator.setRepeatMode(ValueAnimator.RESTART); animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { mCurrentDegree = (int) (0 + (Float) animation.getAnimatedValue()); invalidate(); } }); animator.start(); }}

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流。