两种方式实现类似水波扩散效果，（相比较而言，自定义view的效果更好点，动画实现起来更方便点。）
- 自定义view实现
- 动画实现
自定义view实现
思路分析：通过canvas画圆，每次改变圆半径和透明度，当半径达到一定程度，再次从中心开始绘圆，达到不同层级的效果，通过不断绘制达到view扩散效果
private Paint centerPaint; //中心圆paint
private int radius = 100; //中心圆半径
private Paint spreadPaint; //扩散圆paint
private float centerX;//圆心x
private float centerY;//圆心y
private int distance = 5; //每次圆递增间距
private int maxRadius = 80; //最大圆半径
private int delayMilliseconds = 33;//扩散延迟间隔，越大扩散越慢
private List<Integer> spreadRadius = new ArrayList<>();//扩散圆层级数，元素为扩散的距离
private List<Integer> alphas = new ArrayList<>();//对应每层圆的透明度style文件里自定义属性
<declare-styleable name="SpreadView">
<!--中心圆颜色-->
<attr name="spread_center_color" format="color" />
<!--中心圆半径-->
<attr name="spread_radius" format="integer" />
<!--扩散圆颜色-->
<attr name="spread_spread_color" format="color" />
<!--扩散间距-->
<attr name="spread_distance" format="integer" />
<!--扩散最大半径-->
<attr name="spread_max_radius" format="integer" />
<!--扩散延迟间隔-->
<attr name="spread_delay_milliseconds" format="integer" />
</declare-styleable>初始化
public SpreadView(Context context) {
this(context, null, 0);
}
public SpreadView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public SpreadView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SpreadView, defStyleAttr, 0);
radius = a.getInt(R.styleable.SpreadView_spread_radius, radius);
maxRadius = a.getInt(R.styleable.SpreadView_spread_max_radius, maxRadius);
int centerColor = a.getColor(R.styleable.SpreadView_spread_center_color, ContextCompat.getColor(context, R.color.colorAccent));
int spreadColor = a.getColor(R.styleable.SpreadView_spread_spread_color, ContextCompat.getColor(context, R.color.colorAccent));
distance = a.getInt(R.styleable.SpreadView_spread_distance, distance);
a.recycle();
centerPaint = new Paint();
centerPaint.setColor(centerColor);
centerPaint.setAntiAlias(true);
//最开始不透明且扩散距离为0
alphas.add(255);
spreadRadius.add(0);
spreadPaint = new Paint();
spreadPaint.setAntiAlias(true);
spreadPaint.setAlpha(255);
spreadPaint.setColor(spreadColor);
}确定圆心位置
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//圆心位置
centerX = w / 2;
centerY = h / 2;
}自定义view的绘制
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < spreadRadius.size(); i++) {
int alpha = alphas.get(i);
spreadPaint.setAlpha(alpha);
int width = spreadRadius.get(i);
//绘制扩散的圆
canvas.drawCircle(centerX, centerY, radius + width, spreadPaint);
//每次扩散圆半径递增，圆透明度递减
if (alpha > 0 && width < 300) {
alpha = alpha - distance > 0 ? alpha - distance : 1;
alphas.set(i, alpha);
spreadRadius.set(i, width + distance);
}
}
//当最外层扩散圆半径达到最大半径时添加新扩散圆
if (spreadRadius.get(spreadRadius.size() - 1) > maxRadius) {
spreadRadius.add(0);
alphas.add(255);
}
//超过8个扩散圆，删除最先绘制的圆，即最外层的圆
if (spreadRadius.size() >= 8) {
alphas.remove(0);
spreadRadius.remove(0);
}
//中间的圆
canvas.drawCircle(centerX, centerY, radius, centerPaint);
//TODO 可以在中间圆绘制文字或者图片
//延迟更新，达到扩散视觉差效果
postInvalidateDelayed(delayMilliseconds);
}xml样式
XML
<com.airsaid.diffuseview.widget.SpreadView
android:id="@+id/spreadView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:spread_center_color="@color/colorAccent"
app:spread_delay_milliseconds="35"
app:spread_distance="5"
app:spread_max_radius="90"
app:spread_radius="100"
app:spread_spread_color="@color/colorAccent" />中心圆处可以自定义写文字，画图片等等...
动画实现
思路分析：通过动画实现，imageView不停做动画缩放+渐变
最中心的imageView保持不变
中间一层imageView从原始放大到1.4倍，同时从不透明变为半透明
最外层的imageView从1.4倍放大到1.8倍，同时从半透明变为全透明
利用shape画一个圆，作为动画基础视图
XML
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<corners android:radius="65dp"/>
<solid android:color="@color/colorAccent"/>
</shape>布局视图
XML
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--中心imageView-->
<ImageView
android:id="@+id/iv_wave"
android:layout_width="130dp"
android:layout_height="130dp"
android:layout_gravity="center"
android:background="@drawable/shape_circle" />
<!--中间的imageView-->
<ImageView
android:id="@+id/iv_wave_1"
android:layout_width="130dp"
android:layout_height="130dp"
android:layout_gravity="center"
android:background="@drawable/shape_circle" />
<!--最外层imageView-->
<ImageView
android:id="@+id/iv_wave_2"
android:layout_width="130dp"
android:layout_height="130dp"
android:layout_gravity="center"
android:background="@drawable/shape_circle" />
</FrameLayout>中间imageView的动画
XML
private void setAnim1() {
AnimationSet as = new AnimationSet(true);
//缩放动画，以中心从原始放大到1.4倍
ScaleAnimation scaleAnimation = new ScaleAnimation(1.0f, 1.4f, 1.0f, 1.4f,
ScaleAnimation.RELATIVE_TO_SELF, 0.5f,
ScaleAnimation.RELATIVE_TO_SELF, 0.5f);
//渐变动画
AlphaAnimation alphaAnimation = new AlphaAnimation(1.0f, 0.5f);
scaleAnimation.setDuration(800);
scaleAnimation.setRepeatCount(Animation.INFINITE);
alphaAnimation.setRepeatCount(Animation.INFINITE);
as.setDuration(800);
as.addAnimation(scaleAnimation);
as.addAnimation(alphaAnimation);
iv1.startAnimation(as);
}最外层imageView的动画
XML
private void setAnim2() {
AnimationSet as = new AnimationSet(true);
//缩放动画，以中心从1.4倍放大到1.8倍
ScaleAnimation scaleAnimation = new ScaleAnimation(1.4f, 1.8f, 1.4f, 1.8f,
ScaleAnimation.RELATIVE_TO_SELF, 0.5f,
ScaleAnimation.RELATIVE_TO_SELF, 0.5f);
//渐变动画
AlphaAnimation alphaAnimation = new AlphaAnimation(0.5f, 0.1f);
scaleAnimation.setDuration(800);
scaleAnimation.setRepeatCount(Animation.INFINITE);
alphaAnimation.setRepeatCount(Animation.INFINITE);
as.setDuration(800);
as.addAnimation(scaleAnimation);
as.addAnimation(alphaAnimation);
iv2.startAnimation(as);
}相比较而言，自定义view的效果更好点，动画实现起来更方便点。