Android编程权威指南第三版 第32章

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1.首先，让日落可逆。也就是说，点击屏幕，等太阳落下后，再次点击屏幕，让太阳升起来。 动画集不能逆向执行，因此，你需要新建一个AnimatorSet。

2.第二个挑战是添加太阳动画特效，让它有规律地放大、缩小或是加一圈旋转的光线。（这实际是反复执行一段动画特效，可考虑使用ObjectAnimator的setRepeatCount(int)方法。） 另外，海面上要是有太阳的倒影就更真实了。

3.最后，再来看个颇具挑战的练习。在日落过程中实现动画反转。在太阳慢慢下落时点击屏幕， 让太阳无缝回升至原来所在的位置。或者，在太阳落下进入夜晚时点击屏幕，让太阳重新升回天 空，就像日出。

一、日落可逆

这部分比较简单，根据提示新建新的动画和动画集就可以，直接上代码

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//上升动画 sun_upAnimator = ObjectAnimator.ofFloat(mSunView, "y", sunYFirstEnd,sunYFirstStart).setDuration(3000); sun_upAnimator.setInterpolator(new AccelerateInterpolator()); //上升动画集 sun_upAnimatorSet = new AnimatorSet(); sun_upAnimatorSet.play(sun_upAnimator) .with(sunsetSkyAnimator) .before(nightSkyAnimator);

二、太阳动画特效

这部分主要涉及缩放动画、旋转动画，提示使用ObjectAnimator的setRepeatCount(int)方法，但是我并未使用，我的代码如下

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//变大 bigXAnimator = ObjectAnimator.ofFloat(mSunView,"scaleX",1.0f,2.0f).setDuration(3000); bigYAnimator = ObjectAnimator.ofFloat(mSunView,"scaleY",1.0f,2.0f).setDuration(3000); //变小 smallXAnimator = ObjectAnimator.ofFloat(mSunView,"scaleX",2.0f,1.0f).setDuration(3000); smallYAnimator = ObjectAnimator.ofFloat(mSunView,"scaleY",2.0f,1.0f).setDuration(3000); //旋转特效 //顺时针 clockwiseAnimator = ObjectAnimator.ofFloat(mSunView,"rotation",0f,720f).setDuration(3000); //逆时针 anti_clockwiseAnimator = ObjectAnimator.ofFloat(mSunView,"rotation",360f,0f).setDuration(3000);

旋转动画特别说明：通过旋转sun来实现旋转的光线的效果，所以修改sun.xml给sun加上边框间断线

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<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android = "http://schemas.android.com/apk/res/android" android:shape="oval"> <solid android:color="@color/bright_sun"/> <stroke android:width="2dp" android:color="@color/huawei_red" android:dashWidth="25dp" android:dashGap="8dp"/> </shape>

以上动画直接.with()加到动画集即可。

One more thing：

为了让太阳更真实，添加倒影效果

①在布局文件中，再添加一个FrameLayout，记得android:layout_weight调成0.5，这样sky和sea各一半。

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<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <FrameLayout android:id="@+id/sky" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="0.5" android:background="@color/blue_sky"> <ImageView android:id="@+id/sun" android:layout_width="100dp" android:layout_height="100dp" android:layout_gravity="center" android:src="@drawable/sun" android:contentDescription="@string/todo" /> &l 大专栏  Android编程权威指南第三版 第32章t;/FrameLayout> <FrameLayout android:id="@+id/sea" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="0.5" android:background="@color/sea"> <ImageView android:id="@+id/little_sun" android:layout_width="100dp" android:layout_height="100dp" android:layout_gravity="center" android:src="@drawable/sun" android:contentDescription="@string/todo" android:alpha="0.7"/> </FrameLayout> </LinearLayout>

②倒影需要有位移动画、缩放动画、旋转动画、渐变透明动画。代码如下

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//--------------------------------倒影--------------------------------// //透明度 alphaAnimator = ObjectAnimator.ofFloat(mLittleSunView, "alpha", 0.7f, 0.0f).setDuration(3000); unalphaAnimator = ObjectAnimator.ofFloat(mLittleSunView,"alpha",0.0f,0.7f).setDuration(3000); //大小 little_bigXAnimator = ObjectAnimator.ofFloat(mLittleSunView,"scaleX",1.0f,2.0f).setDuration(3000); little_bigYAnimator = ObjectAnimator.ofFloat(mLittleSunView,"scaleY",1.0f,2.0f).setDuration(3000); little_smallXAnimator = ObjectAnimator.ofFloat(mLittleSunView,"scaleX",2.0f,1.0f).setDuration(3000); little_smallYAnimator = ObjectAnimator.ofFloat(mLittleSunView,"scaleY",2.0f,1.0f).setDuration(3000); //旋转特效 little_clockwiseAnimator = ObjectAnimator.ofFloat(mLittleSunView,"rotation",0f,720f).setDuration(3000); little_anti_clockwiseAnimator = ObjectAnimator.ofFloat(mLittleSunView,"rotation",360f,0f).setDuration(3000); //位移 little_upAnimator = ObjectAnimator.ofFloat(mLittleSunView, "y", littlesunYFirstStart, littlesunYFirstEnd).setDuration(3000); little_upAnimator.setInterpolator(new AccelerateInterpolator()); little_downAnimator = ObjectAnimator.ofFloat(mLittleSunView, "y", littlesunYFirstEnd, littlesunYFirstStart).setDuration(3000); little_downAnimator.setInterpolator(new AccelerateInterpolator());

分别定义太阳下降、太阳上升、倒影下降、倒影上升动画集，再合并为上升、下降总动画集

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//太阳下降动画集 sun_downAnimatorSet = new AnimatorSet(); sun_downAnimatorSet.play(sun_downAnimator) .with(sunsetSkyAnimator) .with(bigXAnimator).with(bigYAnimator) .with(clockwiseAnimator) .before(nightSkyAnimator); //太阳上升动画集 sun_upAnimatorSet = new AnimatorSet(); sun_upAnimatorSet.play(sun_upAnimator) .with(sunsetSkyAnimator) .with(smallXAnimator).with(smallYAnimator) .with(anti_clockwiseAnimator) .before(nightSkyAnimator); //倒影上升动画集、 little_upAnimatorSet = new AnimatorSet(); little_upAnimatorSet .play(little_anti_clockwiseAnimator) .with(little_bigXAnimator).with(little_bigYAnimator) .with(alphaAnimator) .with(little_upAnimator); //倒影下降动画集 little_downAnimatorSet = new AnimatorSet(); little_downAnimatorSet .play(little_clockwiseAnimator) .with(little_smallXAnimator).with(little_smallYAnimator) .with(little_downAnimator) .with(unalphaAnimator); //总动画集 downAnimatorSet = new AnimatorSet(); downAnimatorSet.play(sun_downAnimatorSet).with(little_upAnimatorSet); upAnimatorSet = new AnimatorSet(); upAnimatorSet.play(sun_upAnimatorSet).with(little_downAnimatorSet);

三、日落动画反转

目前暂时还没做。

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关于Android动画用法，推荐这篇https://blog.csdn.net/qq_40881680/article/details/82378391，写得很好，在我学动画部分的时候，对我帮助很大。