https://github.com/XunMengWinter/CircularAnim

Java
Android水波动画帮助类，一行代码实现View显示/隐藏/startActivity特效。(对 ViewAnimationUtils.createCircularReveal() 方法的封装)

CircularAnim

首先来看一个UI动效图。

效果图是是Dribbble上看到的，原作品在此。

我所实现的效果如下： Watch on YouTube

使用方法

为了使用起来简单，我将动画封装成CircularAnimUtil.

现在，让按钮收缩只需一行代码，如下：

CircularAnimUtil.hide(mChangeBtn);

同理，让按钮伸展开：

CircularAnimUtil.show(mChangeBtn);

水波般铺满指定颜色并启动一个Activity:

CircularAnimUtil.startActivity(MainActivity.this, EmptyActivity.class, view, R.color.colorPrimary);

这里，你还可以放图片：

CircularAnimUtil.startActivity(MainActivity.this, EmptyActivity.class, view, R.mipmap.img_huoer_black);

也许在显示或隐藏视图时，你想要设置半径和时长，你可以调用这个方法：

显示：show(View myView, float startRadius, long durationMills)

隐藏：hide(final View myView, float endRadius, long durationMills)

以及，你可以在startActivity时带上Intent:

startActivity(Activity thisActivity, Intent intent, View triggerView, int colorOrImageRes)

还可以startActivityForResult:

startActivityForResult(Activity thisActivity, Intent intent, Integer requestCode, View triggerView, int colorOrImageRes)

同理，startActivity同样可以设置时长。

用起来非常的方便，一切逻辑性的东西都由帮助类搞定。

源码

下面贡献源码。你可以直接新建一个CircularAnimUtil的类，然后把下面的代码复制进去就OK了。

另外，GitHub Demo 地址在此，欢迎Star,欢迎喜欢，欢迎关注，哈哈哈 ^ ^ ~

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.ViewAnimationUtils;
import android.view.ViewGroup;
import android.widget.ImageView;

/**
 * 对 ViewAnimationUtils.createCircularReveal() 方法的封装.
 * <p/>
 * Created on 16/7/20.
 * GitHub: https://github.com/XunMengWinter
 *
 * @author ice
 */
public class CircularAnimUtil {

    public static final long PERFECT_MILLS = 618;
    public static final int MINI_RADIUS = 0;

    /**
     * 向四周伸张，直到完成显示。
     */
    @SuppressLint("NewApi")
    public static void show(View myView, float startRadius, long durationMills) {
        if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.LOLLIPOP) {
            myView.setVisibility(View.VISIBLE);
            return;
        }

        int cx = (myView.getLeft() + myView.getRight()) / 2;
        int cy = (myView.getTop() + myView.getBottom()) / 2;

        int w = myView.getWidth();
        int h = myView.getHeight();

        // 勾股定理 & 进一法
        int finalRadius = (int) Math.sqrt(w * w + h * h) + 1;

        Animator anim =
                ViewAnimationUtils.createCircularReveal(myView, cx, cy, startRadius, finalRadius);
        myView.setVisibility(View.VISIBLE);
        anim.setDuration(durationMills);
        anim.start();
    }

    /**
     * 由满向中间收缩，直到隐藏。
     */
    @SuppressLint("NewApi")
    public static void hide(final View myView, float endRadius, long durationMills) {
        if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.LOLLIPOP) {
            myView.setVisibility(View.INVISIBLE);
            return;
        }

        int cx = (myView.getLeft() + myView.getRight()) / 2;
        int cy = (myView.getTop() + myView.getBottom()) / 2;
        int w = myView.getWidth();
        int h = myView.getHeight();

        // 勾股定理 & 进一法
        int initialRadius = (int) Math.sqrt(w * w + h * h) + 1;

        Animator anim =
                ViewAnimationUtils.createCircularReveal(myView, cx, cy, initialRadius, endRadius);
        anim.setDuration(durationMills);
        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);
                myView.setVisibility(View.INVISIBLE);
            }
        });

        anim.start();
    }

    /**
     * 从指定View开始向四周伸张(伸张颜色或图片为colorOrImageRes), 然后进入另一个Activity,
     * 返回至 @thisActivity 后显示收缩动画。
     */
    @SuppressLint("NewApi")
    public static void startActivityForResult(
            final Activity thisActivity, final Intent intent, final Integer requestCode, final Bundle bundle,
            final View triggerView, int colorOrImageRes, long durationMills) {

        if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.LOLLIPOP) {
            thisActivity.startActivity(intent);
            return;
        }

        int[] location = new int[2];
        triggerView.getLocationInWindow(location);
        final int cx = location[0] + triggerView.getWidth() / 2;
        final int cy = location[1] + triggerView.getHeight() / 2;
        final ImageView view = new ImageView(thisActivity);
        view.setScaleType(ImageView.ScaleType.CENTER_CROP);
        view.setImageResource(colorOrImageRes);
        final ViewGroup decorView = (ViewGroup) thisActivity.getWindow().getDecorView();
        int w = decorView.getWidth();
        int h = decorView.getHeight();
        decorView.addView(view, w, h);

        // 计算中心点至view边界的最大距离
        int maxW = Math.max(cx, w - cx);
        int maxH = Math.max(cy, h - cy);
        final int finalRadius = (int) Math.sqrt(maxW * maxW + maxH * maxH) + 1;
        Animator
                anim = ViewAnimationUtils.createCircularReveal(view, cx, cy, 0, finalRadius);
        int maxRadius = (int) Math.sqrt(w * w + h * h) + 1;
        // 若使用默认时长，则需要根据水波扩散的距离来计算实际时间
        if (durationMills == PERFECT_MILLS) {
            // 算出实际边距与最大边距的比率
            double rate = 1d * finalRadius / maxRadius;
            // 水波扩散的距离与扩散时间成正比
            durationMills = (long) (PERFECT_MILLS * rate);
        }
        final long finalDuration = durationMills;
        anim.setDuration(finalDuration);
        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);

                if (requestCode == null)
                    thisActivity.startActivity(intent);
                else if (bundle == null)
                    thisActivity.startActivityForResult(intent, requestCode);
                else
                    thisActivity.startActivityForResult(intent, requestCode, bundle);

                // 默认渐隐过渡动画.
                thisActivity.overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);

                // 默认显示返回至当前Activity的动画.
                triggerView.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        Animator anim =
                                ViewAnimationUtils.createCircularReveal(view, cx, cy, finalRadius, 0);
                        anim.setDuration(finalDuration);
                        anim.addListener(new AnimatorListenerAdapter() {
                            @Override
                            public void onAnimationEnd(Animator animation) {
                                super.onAnimationEnd(animation);
                                try {
                                    decorView.removeView(view);
                                } catch (Exception e) {
                                    e.printStackTrace();
                                }
                            }
                        });
                        anim.start();
                    }
                }, 1000);

            }
        });
        anim.start();
    }


    /*下面的方法全是重载，用简化上面方法的构建*/


    public static void startActivityForResult(
            Activity thisActivity, Intent intent, Integer requestCode, View triggerView, int colorOrImageRes) {
        startActivityForResult(thisActivity, intent, requestCode, null, triggerView, colorOrImageRes, PERFECT_MILLS);
    }

    public static void startActivity(
            Activity thisActivity, Intent intent, View triggerView, int colorOrImageRes, long durationMills) {
        startActivityForResult(thisActivity, intent, null, null, triggerView, colorOrImageRes, durationMills);
    }

    public static void startActivity(
            Activity thisActivity, Intent intent, View triggerView, int colorOrImageRes) {
        startActivity(thisActivity, intent, triggerView, colorOrImageRes, PERFECT_MILLS);
    }

    public static void startActivity(Activity thisActivity, Class<?> targetClass, View triggerView, int colorOrImageRes) {
        startActivity(thisActivity, new Intent(thisActivity, targetClass), triggerView, colorOrImageRes, PERFECT_MILLS);
    }

    public static void show(View myView) {
        show(myView, MINI_RADIUS, PERFECT_MILLS);
    }

    public static void hide(View myView) {
        hide(myView, MINI_RADIUS, PERFECT_MILLS);
    }

}

后记

需要注意的是，该帮助类适配了api 19以下的版本，因此你不需要判断版本号，但在这些低版本设备上是没有水波动画效果的，不过好的是并不会影响交互逻辑。

另外，有木有手机版或者Mac版好用的Gif转换器推荐，表示好难找。 (感谢im_brucezz、AkiossDev推荐的GIF录制器：licecap，非常好用，上面的gif已经用这个录制了～)

And有没有傻瓜式发布项目到JCenter的教程推荐？看过几篇都不管用。囧 ~