Drawable的使用——LevelListDrawable

LevelListDrawable對應於標籤，它同樣表示一個Drawable集合，集合中每個Drawable都有一個等級(level)的概念。根據不通的等級，LevelListDrawable會顯示對應的Drawable

<?xml version="1.0" encoding="utf-8"?>
<level-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:drawable="@drawable/ic_sunny"
        android:maxLevel="10"
        android:minLevel="0" />
    <item
        android:drawable="@drawable/ic_night"
        android:maxLevel="20"
        android:minLevel="11" />
    <item
        android:drawable="@drawable/ic_cloudy"
        android:maxLevel="30"
        android:minLevel="21" />
</level-list>

     var count = 0
        iv_level_list.setOnClickListener {
            count++
            when (count % 3) {
                0 -> iv_level_list.drawable.level = 5
                1 -> iv_level_list.drawable.level = 15
                2 -> iv_level_list.drawable.level = 25
            }
        }

效果如下：