android实现波纹效果

前几天公司需要做录音的波纹效果，原理很简单：定义一个记录所有同心圆半径的list,只要动态改变list的size，然后遍历之，并以每一个半径绘制圆(drawCircle)， 通过在onDraw方法里面不停invalidate就可以了,代码如下：

package com.example.test.util;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;

import com.example.test.R;

import java.util.ArrayList;
import java.util.List;

/**
* Created by jisj on 6/1/16.
*/
public class RecordView extends View {
public RecordView(Context context) {
this(context, null, 0);
}

public RecordView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public RecordView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
this.context = context;
init();
}

public void setIsWaving(boolean waving){
isWaving = waving;
postInvalidate();
}

private void init() {
paint = new Paint();
paint.setColor(Color.parseColor("#ff6666"));
paint.setAntiAlias(true);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
setMeasuredDimension(width = 600, height = 600);
initOtherSize();
initStartCircle();
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int count = radiusList.size();
//先绘制波纹
if(isWaving){
for (int i = 0; i < count; i++) {
int radius = radiusList.get(i);
float alpha = alphaList.get(i);
paint.setAlpha((int) alpha);
canvas.drawCircle(width / 2, height / 2, radius, paint);
//宽度递增，透明度递减，宽度到最大时，透明度正好为0，singleAlpha保证了最外层的圆消失时不会突兀
if (alpha - singleAlpha >= 0)
alphaList.set(i, alpha - singleAlpha);
if (radius + 1 < this.width / 2) {
radiusList.set(i, radius + 1);
}
}
}

//再绘制中间的图片
Drawable drawable = context.getResources().getDrawable(R.drawable.center_pic);
drawable.setBounds((width - centerWidth) / 2, (height - centerWidth) / 2, (width + centerWidth) / 2, (height + centerWidth) / 2);
drawable.draw(canvas);
if(isWaving){
//如果没有达到最多的圆数，则加一个最内层的圆
if (count <= MAX_CIRCLE_COUNT) {
//这里的width / (MAX_CIRCLE_COUNT * 7)是相邻波纹的半径差值
if (radiusList.size() <= 0 || radiusList.get(radiusList.size() - 1) == centerWidth / 2 + width / (MAX_CIRCLE_COUNT * 7)) {
addInnerCircle();
}
}
//去掉最外层的圆
if (radiusList.size() > MAX_CIRCLE_COUNT) {
radiusList.remove(0);
alphaList.remove(0);
}
//执行onDraw的不断循环
postInvalidate();
}
}

private void initStartCircle() {
clearDataList(alphaList);
clearDataList(radiusList);
alphaList.add(ORIGIN_ALPHA);
radiusList.add(startRadius);
}

private void initOtherSize() {
centerWidth = (int) (width * 0.54f);
//startRadius比centerWidth略小，是为了保证起始圆环出场时藏在中心图片下面，不然会太突然
startRadius = centerWidth / 2 - 30;
//圆环每增加1个像素，则透明度减低的值
singleAlpha = ORIGIN_ALPHA / ((width / 2 - startRadius));
}

private void addInnerCircle() {
alphaList.add(ORIGIN_ALPHA);
radiusList.add(startRadius);
}

private void clearDataList(List list) {
if (list.size() > 0)
list.clear();
}

private ArrayList<Float> alphaList = new ArrayList<Float>();
private ArrayList<Integer> radiusList = new ArrayList<Integer>();

private int width, height;
private float singleAlpha = 1;                      //圆环每增加1个像素，则透明度减低的值
private int centerWidth;                            //中间固定图片的半径
private int startRadius;                            //起始圆环的半径
private boolean isWaving = false;
private Paint paint;
private Context context;

private static final float ORIGIN_ALPHA = 150;      //最内层圆环的透明度
private static final int MAX_CIRCLE_COUNT = 5;      //最多的圆环数量

}

代码中用到的图片，是百度搜到的，如果有侵权。。。。。对不起啊大哥