AlphaAnimation漸變動畫只需要設定從一可見程度，到另一可見程度即可。

示例程式碼：

package com.hongchou.www.myalphaanimation;

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Window;
import android.view.animation.AlphaAnimation;
import android.widget.ImageView;

/**
 * android AlphaAnimation漸變動畫
 */
 

public class MainActivity extends Activity {

    private ImageView iv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        iv = findViewById(R.id.iv);
        AlphaAnimation alphaAnimation=new
 
 AlphaAnimation(0,1);
        alphaAnimation.setDuration(2000);
        iv.startAnimation(alphaAnimation);
    }
}

佈局檔案程式碼：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
 

    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.hongchou.www.myalphaanimation.MainActivity">

    <ImageView
        android:id="@+id/iv"
        android:background="@drawable/bk"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

注意設定動畫時間，才能看到動畫效果

 alphaAnimation.setDuration(2000);