語法結構：

<?xml version="1.0" encoding="utf-8"?>
<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape=["rectangle" | "oval" | "line" | "ring"] >
    <corners
        android:radius="integer"
        android:topLeftRadius="integer"
        android:topRightRadius="integer"
        android:bottomLeftRadius="integer"
        android:bottomRightRadius="integer" />
    <gradient
        android:angle="integer"
        android:centerX="integer"
        android:centerY="integer"
        android:centerColor="integer"
        android:endColor="color"
        android:gradientRadius="integer"
        android:startColor="color"
        android:type=["linear" | "radial" | "sweep"]
        android:useLevel=["true" | "false"] />
    <padding
        android:left="integer"
        android:top="integer"
        android:right="integer"
        android:bottom="integer" />
    <size
        android:width="integer"
        android:height="integer" />
    <solid
        android:color="color" />
    <stroke
        android:width="integer"
        android:color="color"
        android:dashWidth="integer"
        android:dashGap="integer" />
</shape>
 

元素屬性：

android:shape

Defines the type of shape. Valid values are:（定義這個型別的形狀，變數值是：）

Value	Desciption
"rectangle"	A rectangle （長方形）that fills the containing View. This is the default shape.（這個是預設的形狀）
"oval"	An oval （橢圓形）shape that fits the dimensions of the containing View.
"line"	A horizontalline that spans the width of the containing View. This shape requires the <stroke>  element to define the width of the line.
"ring"	A ring shape.(環形)

1.rectangle屬性

可用於製作按鈕等控制元件背景，如：常用圓角背景框、漸變色背景、透明背景層......；

如上圖所示，只需設定solid屬性顏色值為#60000000，即可為TextView設定半透明背景層了。

如果在TextView或者父容器中使用alpha=0.5，將會導致文字內容也呈現半透明效果，顯然不是設計所需！

如果使用RelativeLayout佈局，多使用一個半透明背景層View也能實現上圖效果，但操作繁瑣，不太理想！

2.line屬性

可用於製作分隔線（漸變色分隔線）

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="line" >
    <stroke
        android:width="4dp"
        android:color="@android:color/black" />
</shape>

3.ring屬性

       The following attributes are used only when android:shape="ring":

android:innerRadius

Dimension. The radius for the inner part of the ring (the hole in the middle), as a dimension value or dimension resource.

android:innerRadiusRatio

Float. The radius for the inner part of the ring, expressed as a ratio of the ring's width. For instance, if android:innerRadiusRatio="5", then the inner radius equals the ring's width divided by 5. This value is overridden by android:innerRadius. Default value is 9.

android:thickness

Dimension. The thickness of the ring, as a dimension value or dimension resource.

android:thicknessRatio

Float. The thickness of the ring, expressed as a ratio of the ring's width. For instance, if android:thicknessRatio="2", then the thickness equals the ring's width divided by 2. This value is overridden by android:innerRadius. Default value is 3.

android:useLevel

Boolean. "true" if this is used as a . This should normally be "false" or your shape may not appear.

<corners> Creates rounded corners for the shape. Applies only when the shape is a rectangle.建立圓角的形狀。僅適用於當其形狀是一個長方形。

attributes:

android:radius

Dimension. The radius for all corners, as a dimension value or dimension resource. This is overridden for each corner by the following attributes.

android:topLeftRadius

Dimension. The radius for the top-left corner, as a dimension value or dimension resource.

android:topRightRadius

Dimension. The radius for the top-right corner, as a dimension value or dimension resource.

android:bottomLeftRadius

Dimension. The radius for the bottom-left corner, as a dimension value or dimension resource.

android:bottomRightRadius

Dimension. The radius for the bottom-right corner, as a dimension value or dimension resource.

Note: Every corner must (initially) be provided a corner radius greater than 1, or else no corners are rounded. If you want specific corners to notbe rounded, a work-around is to use android:radius to set a default corner radius greater than 1, but then override each and every corner with the values you really want, providing zero ("0dp") where you don't want rounded corners.

<gradient> Specifies a gradient color for the shape.指定一個漸變顏色的形狀。

attributes:

android:angle

Integer. The angle for the gradient, in degrees. 0 is left to right, 90 is bottom to top. It must be a multiple of 45. Default is 0.

android:centerX

Float. The relative X-position for the center of the gradient (0 - 1.0).

android:centerY

Float. The relative Y-position for the center of the gradient (0 - 1.0).

android:centerColor

Color. Optional color that comes between the start and end colors, as a hexadecimal value or color resource.

android:endColor

Color. The ending color, as a hexadecimal value or color resource.

android:gradientRadius

Float. The radius for the gradient. Only applied when android:type="radial".

android:startColor

Color. The starting color, as a hexadecimal value or color resource.

android:type

Keyword. The type of gradient pattern to apply. Valid values are:

Value	Description
"linear"	A linear gradient. This is the default.
"radial"	A radial gradient. The start color is the center color.
"sweep"	A sweeping line gradient.

android:useLevel

Boolean. "true" if this is used as a .

<padding> Padding to apply to the containing View element (this pads the position of the View content, not the shape).適用於包含填充檢視元素(這墊的位置,而不是觀點內容的形狀)

attributes:

android:left

Dimension. Left padding, as a dimension value or dimension resource.

android:top

Dimension. Top padding, as a dimension value or dimension resource.

android:right

Dimension. Right padding, as a dimension value or dimension resource.

android:bottom

Dimension. Bottom padding, as a dimension value or dimension resource.

<size> The size of the shape.

attributes:

android:height

Dimension. The height of the shape, as a dimension value or dimension resource.

android:width

Dimension. The width of the shape, as a dimension value or dimension resource.

Note: The shape scales to the size of the container View proportionate to the dimensions defined here, by default. When you use the shape in an , you can restrict scaling by setting the android:scaleType to "center".

<solid> A solid color to fill the shape.

attributes:

android:color

Color. The color to apply to the shape, as a hexadecimal value or color resource.

<stroke> A stroke line for the shape.

attributes:

android:width

Dimension. The thickness of the line, as a dimension value or dimension resource.

android:color

Color. The color of the line, as a hexadecimal value or color resource.

android:dashGap

Dimension. The distance between line dashes, as a dimension value or dimension resource. Only valid if android:dashWidth is set.

android:dashWidth

Dimension. The size of each dash line, as a dimension value or dimension resource. Only valid if android:dashGap is set.

gradient   -- 對應顏色漸變。 startcolor、endcolor就不多說了。 android:angle 是指從哪個角度開始變。

gradient：漸變
android:startColor和android:endColor分別為起始和結束顏色，android:angle是漸變角度，必須為45的整數倍。
另外漸變預設的模式為android:type="linear"，即線性漸變，可以指定漸變為徑向漸變，android:type="radial"，徑向漸變需要指定半徑android:gradientRadius="50"。

solid      --  填充。

solid：實心，就是填充的意思android:color指定填充的顏色

stroke   --  描邊。

stroke：描邊
android:width="2dp" 描邊的寬度，android:color 描邊的顏色。
我們還可以把描邊弄成虛線的形式，設定方式為：
android:dashWidth="5dp" 
android:dashGap="3dp"
其中android:dashWidth表示'-'這樣一個橫線的寬度，android:dashGap表示之間隔開的距離。

corners  --  圓角。

corners：圓角
android:radius為角的弧度，值越大角越圓。
我們還可以把四個角設定成不同的角度，方法為：
<corners 
        android:topRightRadius="20dp"    右上角
        android:bottomLeftRadius="20dp"    右下角
        android:topLeftRadius="1dp"    左上角
        android:bottomRightRadius="0dp"    左下角
 />
這裡有個地方需要注意，bottomLeftRadius是右下角，而不是左下角!