Android 自定义属性用法详解
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Android 自定义属性用法详解
TedYin 发表于4年前
Android 自定义属性用法详解
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摘要: Android自定义属性的含义及用法详解

最近项目中经常需要用到自定义控件,因此自定义属性也是经常要用到的,在此说明一下自定义属性的用法:

自定义属性都存在于/value/attr.xml文件中,以如下格式存在。

    <resource>

        <declare-styleable name="自定义属性名称">

            <attr name="属性名称" format="属性种类"/>

                ......

        </declare-styleable>

    </resource>

对于自定义属性中的format的值及其含义如下:

format属性值:reference 、color、boolean、dimension、float、integer、string、fraction、enum、flag

1. reference:参考某一资源ID。

    (1)属性定义:

            <declare-styleable name = "名称">

                   <attr name = "background" format = "reference" />

            </declare-styleable>

    (2)属性使用:

             <ImageView

                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:background = "@drawable/图片ID"

                     />

2. color:颜色值。

    (1)属性定义:

            <declare-styleable name = "名称">

                   <attr name = "textColor" format = "color" />

            </declare-styleable>

    (2)属性使用:

            <TextView

                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:textColor = "#00FF00"

                     />

3. boolean:布尔值。

    (1)属性定义:

            <declare-styleable name = "名称">

                   <attr name = "focusable" format = "boolean" />

            </declare-styleable>

    (2)属性使用:

            <Button

                    android:layout_width = "42dip"
                    android:layout_height = "42dip"

                    android:focusable = "true"

                    />

4. dimension:尺寸值。

    (1)属性定义:

            <declare-styleable name = "名称">

                   <attr name = "layout_width" format = "dimension" />

            </declare-styleable>

    (2)属性使用:

            <Button

                    android:layout_width = "42dip"
                    android:layout_height = "42dip"

                    />

5. float:浮点值。

    (1)属性定义:

            <declare-styleable name = "AlphaAnimation">

                   <attr name = "fromAlpha" format = "float" />
                   <attr name = "toAlpha" format = "float" />

            </declare-styleable>

    (2)属性使用:

            <alpha
                   android:fromAlpha = "1.0"
                   android:toAlpha = "0.7"

                   />

6. integer:整型值。

    (1)属性定义:

            <declare-styleable name = "AnimatedRotateDrawable">

                   <attr name = "visible" />
                   <attr name = "frameDuration" format="integer" />
                   <attr name = "framesCount" format="integer" />
                   <attr name = "pivotX" />
                   <attr name = "pivotY" />
                   <attr name = "drawable" />

            </declare-styleable>

    (2)属性使用:

            <animated-rotate

                   xmlns:android = "http://schemas.android.com/apk/res/android
                   android:drawable = "@drawable/图片ID" 
                   android:pivotX = "50%" 
                   android:pivotY = "50%" 
                   android:framesCount = "12" 
                   android:frameDuration = "100"

                   />

7. string:字符串。

    (1)属性定义:

            <declare-styleable name = "MapView">
                   <attr name = "apiKey" format = "string" />
            </declare-styleable>

    (2)属性使用:

            <com.google.android.maps.MapView
                    android:layout_width = "fill_parent"
                    android:layout_height = "fill_parent"
                    android:apiKey = "0jOkQ80oD1JL9C6HAja99uGXCRiS2CGjKO_bc_g"

                    />

8. fraction:百分数。

    (1)属性定义:

            <declare-styleable name="RotateDrawable">
                   <attr name = "visible" />
                   <attr name = "fromDegrees" format = "float" />
                   <attr name = "toDegrees" format = "float" />
                   <attr name = "pivotX" format = "fraction" />
                   <attr name = "pivotY" format = "fraction" />
                   <attr name = "drawable" />
            </declare-styleable>

    (2)属性使用:

            <rotate

                   xmlns:android = "http://schemas.android.com/apk/res/android"
               android:interpolator = "@anim/动画ID"

                   android:fromDegrees = "0"
               android:toDegrees = "360"

                   android:pivotX = "200%"

                   android:pivotY = "300%"
               android:duration = "5000"

                   android:repeatMode = "restart"

                   android:repeatCount = "infinite"

                   />

9. enum:枚举值。

    (1)属性定义:

            <declare-styleable name="名称">
                   <attr name="orientation">
                          <enum name="horizontal" value="0" />
                          <enum name="vertical" value="1" />
                   </attr>           

            </declare-styleable>

    (2)属性使用:

            <LinearLayout

                    xmlns:android = "http://schemas.android.com/apk/res/android"
                    android:orientation = "vertical"
                    android:layout_width = "fill_parent"
                    android:layout_height = "fill_parent"
                    >
            </LinearLayout>

10. flag:位或运算。

     (1)属性定义:

             <declare-styleable name="名称">
                    <attr name="windowSoftInputMode">
                            <flag name = "stateUnspecified" value = "0" />
                            <flag name = "stateUnchanged" value = "1" />
                            <flag name = "stateHidden" value = "2" />
                            <flag name = "stateAlwaysHidden" value = "3" />
                            <flag name = "stateVisible" value = "4" />
                            <flag name = "stateAlwaysVisible" value = "5" />
                            <flag name = "adjustUnspecified" value = "0x00" />
                            <flag name = "adjustResize" value = "0x10" />
                            <flag name = "adjustPan" value = "0x20" />
                            <flag name = "adjustNothing" value = "0x30" />
                     </attr>        

             </declare-styleable>

     (2)属性使用:

            <activity

                   android:name = ".StyleAndThemeActivity"
                   android:label = "@string/app_name"
                   android:windowSoftInputMode = "stateUnspecified | stateUnchanged | stateHidden">
                   <intent-filter>
                          <action android:name = "android.intent.action.MAIN" />
                          <category android:name = "android.intent.category.LAUNCHER" />
                   </intent-filter>
             </activity>

特别要注意:

     属性定义时可以指定多种类型值。

    (1)属性定义:

            <declare-styleable name = "名称">

                   <attr name = "background" format = "reference|color" />

            </declare-styleable>

    (2)属性使用:

             <ImageView

                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:background = "@drawable/图片ID|#00FF00"

                     />

下面说说AttributeSet与TypedArray在自定义控件中的作用:

AttributeSet的作用就是在控件进行初始化的时候,解析布局文件中该控件的属性(key eg:background)与该值(value eg:@drawable/icon)的信息封装在AttributeSet中,传递给该控件(View)的构造函数。对于非Android自带的属性,在View类中处理时是无法识别的,因此需要我们自己解析。所以这就要用到另外一个类TypedArray。在AttributeSet中我们有属性名称,有属性值,但是控件如何知道哪个属性代表什么意思呢?这个工作就由TypedArray来做了。TypedArray对象封装了/values/attrs.xml中的styleable里定义的每个属性的类型信息,通过TypedArray我们就可以知道AttributeSet中封装的值到底是干什么的了,从而可以对这些数据进行应用。

AttributeSet就相当于一盒糖,TypedArray就相当于这盒糖上的标签说明,告诉用户每个糖的口味等。这盒糖有什么口味是由用户自己的styleable文件里面的内容来决定的。




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