Android实现水波纹特效

最近需要做个类似于水波纹动画的效果，思考了一下不需要ui切个动态图，android原生的技术利用动画或者自定义控件都可以实现，下面上个图类似于这样的效果

下面请看第一种动画实现，这种方式较为简单些，就是利用3个imageview不断地做缩放和渐变的动画。

布局文件定义一下

<relativelayout
  android:id="@+id/rl"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:gravity="center"
  android:layout_marginbottom="160dp">
  <!--中心imageview-->
  <imageview
    android:id="@+id/iv_wave"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:layout_centerhorizontal="true"
    android:background="@drawable/shape_circle" />
  <!--中间的imageview-->
  <imageview
    android:id="@+id/iv_wave_1"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:layout_centerhorizontal="true"
    android:background="@drawable/shape_circle" />
  <!--最外层imageview-->
  <imageview
    android:id="@+id/iv_wave_2"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:layout_centerhorizontal="true"
    android:background="@drawable/shape_circle" />
</relativelayout>

接下来中间的imageview保持不变，通过操作另外两个imageview达到效果

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);
}
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);
}

接下来就是第二种自定义动画实现

首先定义style文件自定义属性--在values下创建attrs.xml文件

<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>

接下来创建spreadview继承view,初始化构造方法

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);
}

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);
  //延迟更新，达到扩散视觉差效果
  postinvalidatedelayed(delaymilliseconds);
}

最后在activity的布局文件中引用自定义属性：

<com.example.louliang.spread.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="150"
  app:spread_spread_color="@color/coloraccent" />

以上两种方法就实现了水波纹的效果，下载完整的demo请点击链接，希望对大家有所帮助。

源码下载：android实现水波纹特效

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