Android实现渐变色的圆弧虚线效果
投稿：daisy
最近在学习Android的paint类的时候，学习了PathEffect路径效果和Shader渲染效果。所以就做了下面的一个效果，其中自定义的view组主要是用DashPathEffect、SweepGradient的API形成的效果。感兴趣的朋友们可以参考借鉴，下面来一起看看吧。
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。