1、效果：箭头图标由原来位置向上移动，同时改变alpha值变小。（这个效果即提示用户向上滑动屏幕）
2、布局代码activity_down.xml
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <ImageView android:id="@+id/img_down" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@mipmap/down" android:layout_alignParentBottom="true" android:layout_marginBottom="30dp" android:layout_centerHorizontal="true" /> </RelativeLayout>3、动画代码down_anim.xml <?xml version="1.0" encoding="utf-8"?> <set xmlns:android="http://schemas.android.com/apk/res/android" android:interpolator="@android:anim/accelerate_interpolator" android:shareInterpolator="true" android:duration="1000" > <alpha android:fromAlpha="1" android:toAlpha="0.5" android:repeatCount="infinite" android:repeatMode="reverse" /> <!-- <scale android:fromXScale="100%" android:fromYScale="100%" android:toXScale="80%" android:toYScale="80%" android:pivotX="50%" android:pivotY="50%" android:repeatCount="infinite" android:repeatMode="reverse" />--> <translate android:fromXDelta="0%" android:toXDelta="0%" android:fromYDelta="0%" android:toYDelta="-30%" android:repeatCount="infinite" android:repeatMode="reverse" /> </set> 4、activity代码 package ivan.com.appbackendtest; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.animation.AnimationSet; import android.view.animation.AnimationUtils; import android.widget.ImageView; public class DownActivity extends AppCompatActivity { private ImageView img_down; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_down); img_down = (ImageView)findViewById(R.id.img_down); AnimationSet animationSet = (AnimationSet)AnimationUtils.loadAnimation(this, R.anim.down_anim); img_down.startAnimation(animationSet); } } 5、结束，动画代码的参数说明请访问 Android 三种动画详解
