Android渐变色的圆弧虚线
Draco
7年前
<p>在学习Android的paint类的时候学习了 PathEffect 路径效果和 Shader 渲染效果。做了下面的一个效果的自定义的view组主要是用DashPathEffect、SweepGradient的API形成的效果。下面是效果图：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/f57a049634cffaa424a39e65f0e5d4e6.png"></p> <p style="text-align:center">Android渐变色的圆弧虚线</p> <p><strong>1，SweepGradient(梯度渲染)</strong></p> <p><strong>public SweepGradient (float cx, float cy, int[] colors, float[] positions)</strong></p> <p>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：</p> <p><strong>cx：</strong>扫描的中心x坐标</p> <p><strong>cy：</strong>扫描的中心y坐标</p> <p><strong>colors：</strong>梯度渐变的颜色数组</p> <p><strong>positions：</strong>指定颜色数组的相对位置</p> <pre> <code class="language-java">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);</code></pre> <p>效果图：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/1ab8a94df521339fe4f125a0980ed3d5.png"></p> <p style="text-align:center">SweepGradient</p> <p><strong>2，DashPathEffect(Path的线段虚线化)</strong></p> <p><strong>DashPathEffect(float[] intervals, float phase)</strong></p> <p><strong>intervals：</strong>为虚线的ON和OFF的数组，数组中元素数目需要 >= 2</p> <p><strong>phase：</strong>为绘制时的偏移量</p> <pre> <code class="language-java">//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);</code></pre> <p>效果图：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/2c7d13c5057e28d7489e756cc7208c5a.png"></p> <p style="text-align:center">DashPathEffect</p> <p><strong>3，下面是全部的代码：</strong></p> <pre> <code class="language-java">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(); } }</code></pre> <p> </p> <p>来自：http://www.jianshu.com/p/92bf75e41fff</p> <p> </p>