Android 图层列表、 LayerDrawable 、 layer-list \ 改变 seekbar thumb 滑块的颜色-编程知识

android 官网：图层列表 LayerDrawable / layer-list

LayerDrawable 是管理其他可绘制对象数组的可绘制对象。列表中的每个可绘制对象均按照列表顺序绘制。列表中的最后一个可绘制对象绘于顶部。

每个可绘制对象均由单个 <layer-list> 元素内的 <item> 元素表示。

文件位置：

res/drawable/filename.xml

文件名即为资源 ID

编译后的资源数据类型：

指向 LayerDrawable 的资源指针

资源引用：

在 Java 中：R.drawable.filename
在 XML 中：@[package:]drawable/filename

语法：

<?xml version="1.0" encoding="utf-8"?>
<layer-listxmlns:android="http://schemas.android.com/apk/res/android" ><itemandroid:drawable="@[package:]drawable/drawable_resource"android:id="@[+][package:]id/resource_name"android:top="dimension"android:right="dimension"android:bottom="dimension"android:left="dimension" />
</layer-list>

元素：

<layer-list>
必需。该元素必须是根元素。包含一个或多个 <item> 元素。
属性：xmlns:android字符串。必需。定义 XML 命名空间，该命名空间必须为 "http://schemas.android.com/apk/res/android"。<item>
定义放于图层可绘制对象中的可绘制对象，位置由其属性定义。
必须为 <layer-list> 元素的子项。接受子级 <bitmap> 元素。
属性：android:drawable可绘制资源。必需。引用可绘制资源。android:id资源 ID。此可绘制对象的唯一资源 ID。如要为此项创建新的资源 ID，请使用以下形式："@+id/name"。加号表示其是作为新 ID 创建的。您可以使用此 ID 检索和修改拥有 View.findViewById() 或 Activity.findViewById() 的可绘制对象。android:top尺寸。顶部偏移量，采用尺寸值或尺寸资源的形式。android:right尺寸。右侧偏移量，采用尺寸值或尺寸资源的形式。android:bottom尺寸。底部偏移量，采用尺寸值或尺寸资源的形式。android:left尺寸。左侧偏移量，采用尺寸值或尺寸资源的形式。默认情况下，所有可绘制项都会缩放以适应所包含视图的大小。
因此，将图像放在图层列表中的不同位置可能会增大视图的大小，并且有些图像会相应地缩放。为避免缩放列表中的项，请在 <item> 元素内使用 <bitmap> 元素指定可绘制对象，
并且针对某些不缩放的项（例如 "center"）定义重心。
例如，以下 <item> 定义了缩放以适应其容器视图的项：<item android:drawable="@drawable/image" />为避免缩放，以下示例使用重心居中的 <bitmap> 元素：<item><bitmap android:src="@drawable/image"android:gravity="center" />
</item>

示例：

保存在 res/drawable/layers.xml 的 XML 文件：

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android"><item><bitmap android:src="@drawable/android_red"android:gravity="center" /></item><item android:top="10dp" android:left="10dp"><bitmap android:src="@drawable/android_green"android:gravity="center" /></item><item android:top="20dp" android:left="20dp"><bitmap android:src="@drawable/android_blue"android:gravity="center" /></item>
</layer-list>

此示例使用嵌套的 <bitmap> 元素为每个具有 "center" 重心的项定义可绘制资源。
这可确保不会有图像为适应容器的大小而缩放，因为偏移图像会造成大小调整。

此布局 XML 会将可绘制对象应用到视图：

<ImageViewandroid:layout_height="wrap_content"android:layout_width="wrap_content"android:src="@drawable/layers" />

结果是一堆不断偏移的图像：

在这里插入图片描述

demo1 ：

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android"><!--    圆环  --><item><shapeandroid:dither="true"android:shape="oval"><solid android:color="@color/white" /><strokeandroid:width="1dp"android:color="@android:color/holo_blue_dark" /></shape></item><!--    圆心  --><itemandroid:bottom="20dp"android:left="20dp"android:right="20dp"android:top="20dp"><shape android:shape="oval"><solid android:color="@android:color/holo_blue_dark" /><sizeandroid:width="30dp"android:height="30dp" /></shape></item>
</layer-list>

效果：

在这里插入图片描述

demo2 : 可更新seekbar thumb的颜色

定义 icon_thumb.xml:

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android"><item android:id="@+id/layer_drawable_1"><bitmapandroid:gravity="center"android:src="@drawable/slider_color" /></item><item android:id="@+id/layer_drawable_2"><bitmapandroid:gravity="center"android:src="@drawable/slider_border" /></item>
</layer-list>

drawable-xhdpi/slider_color :

在这里插入图片描述

drawable-xhdpi/slider_border :

在这里插入图片描述

引用：

<SeekBarandroid:id="@+id/seekbar1"android:layout_width="368dp"android:layout_height="44dp"android:layout_marginVertical="20dp"android:background="@drawable/bg_color127"android:max="126"android:progress="0"android:progressDrawable="@android:color/transparent"android:thumb="@drawable/icon_thumb"android:thumbOffset="23dp" />

改变thumb的图层颜色

注意：如果单纯改变整个thumb，直接 seekBar.getThumb().setColorFilter(color, PorterDuff.Mode.SRC_ATOP); 即可

下面是改变thumb的图层中某层的颜色：

SeekBar seekBar = (SeekBar) this.findViewById(R.id.seekbar1);
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {@Overridepublic void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {String colorStr = AmbientUtil.COLORS_127[progress];int color = Color.parseColor(colorStr);Drawable thumb = seekBar.getThumb();if (thumb instanceof LayerDrawable) {LayerDrawable thumb1 = (LayerDrawable) thumb;int numberOfLayers = thumb1.getNumberOfLayers();Drawable drawableByLayerId1 = thumb1.findDrawableByLayerId(R.id.layer_drawable_1);drawableByLayerId1.setColorFilter(color, PorterDuff.Mode.SRC_IN);Log.e(TAG, "onProgressChanged: =================" + numberOfLayers);}//int color = Color.parseColor(colorStr);//Drawable thumb = mColorPickerSeekbar.getThumb();//if (thumb instanceof LayerDrawable) {//		LayerDrawable layerDrawable = (LayerDrawable) thumb;//		Drawable drawable = layerDrawable.findDrawableByLayerId(R.id.layer_drawable_1);//		drawable.setColorFilter(new SimpleColorFilter(color));//}}@Overridepublic void onStartTrackingTouch(SeekBar seekBar) {}@Overridepublic void onStopTrackingTouch(SeekBar seekBar) {}
});

效果：

在这里插入图片描述

其他：

public class AmbientUtil {public static final String[] COLORS_127 = new String[]{"#FFDF85FF", "#FFD869FF", "#FFD253FF", "#FFD038FF", "#FFB123DD", "#FFA24DD7", "#FF8B4FE3", "#FF8A20F9", "#FF7544D8", "#FF5C39DB","#FF4520E0", "#FF0024EC", "#FF193AFF", "#FF225CFE", "#FF0277F8", "#FF008BFE", "#FF3690FC", "#FF2A99FE", "#FF00A3FE", "#FF02A7FF","#FF19ADFF", "#FF0CB2FC", "#FF04B4F2", "#FF0AB7F3", "#FF03C2EF", "#FF01CFF1", "#FF02D7F4", "#FF02DBFE", "#FF22DFFE", "#FF44E8FE","#FF02F0FC", "#FF01FEFF", "#FF38FFFE", "#FF19FDFE", "#FF01FCFF", "#FF44FBFE", "#FF76FEFE", "#FF90FEFB", "#FF8FFFF4", "#FFA0FFF5","#FF8BFFF9", "#FF75FFFC", "#FF85FFF6", "#FF9DFFF9", "#FFAAFFF0", "#FFAAFFE6", "#FFAAFFDC", "#FFA8FAD0", "#FF96F2C0", "#FF7EF6BA","#FF6EEFB1", "#FF6EEEA1", "#FF32ED96", "#FF2BED7E", "#FF15E658", "#FF18E032", "#FF53F204", "#FF6AFB29", "#FF94FF43", "#FFAAFB68","#FFC0F987", "#FFC8FD8D", "#FFD2FA78", "#FFDFF974", "#FFE6FF74", "#FFF2FF74", "#FFF8FF8D", "#FFFFFD9B", "#FFFDFF96", "#FFFFFC87","#FFFFF596", "#FFFFE28C", "#FFFEE687", "#FFFEF086", "#FFFCF588", "#FFFEFC85", "#FFFFFF82", "#FFFCFA66", "#FFFCFC64", "#FFFCFE4F","#FFFFFC4F", "#FFFCFC55", "#FFFCFA6D", "#FFFFF654", "#FFFEF200", "#FFFAE800", "#FFF2D144", "#FFF1C91E", "#FFF1BD29", "#FFF1B934","#FFF3B34B", "#FFF9A845", "#FFFBA04B", "#FFFB964B", "#FFFB8B4B", "#FFFB864D", "#FFFB7F4E", "#FFFC7B4F", "#FFFB774F", "#FFFF724F","#FFFF6C4E", "#FFFF4B4E", "#FFFF364E", "#FFFF0048", "#FFFF0C52", "#FFFF2563", "#FFFA3871", "#FFF7387A", "#FFFA4B7A", "#FFFF587D","#FFFC6587", "#FFFD718A", "#FFFF8599", "#FFFF9FAF", "#FFFFC9D2", "#FFFFFFFF", "#FFFBFFFF", "#FFF3FEFF", "#FFEBFEFF", "#FFEAFDFF","#FFD9FAFF", "#FFC9F7FF", "#FFB3FAFF", "#FFAEF8FF", "#FF97F5FF", "#FF75F2FF", "#FF65F0FF",};
}

bg_color127 :

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