Android 自定義屬性用法詳解

最近項目中常常須要用到自定義控件，所以自定義屬性也是常常要用到的，在此說明一下自定義屬性的用法：

自定義屬性都存在於/value/attr.xml文件中，以以下格式存在。

    <resource>

        <declare-styleable name="自定義屬性名稱">

            <attr name="屬性名稱" format="屬性種類"/>

                ......

        </declare-styleable>

    </resource>

對於自定義屬性中的format的值及其含義以下：

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

1. reference：參考某一資源ID。

    （1）屬性定義：

            <declare-styleable name = "名稱">

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

            </declare-styleable>

    （2）屬性使用：

             <ImageView

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

                     />

2. color：顏色值。

    （1）屬性定義：

            <declare-styleable name = "名稱">

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

            </declare-styleable>

    （2）屬性使用：

            <TextView

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

                     />

3. boolean：布爾值。

    （1）屬性定義：

            <declare-styleable name = "名稱">

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

            </declare-styleable>

    （2）屬性使用：

            <Button

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

                    android:focusable = "true"

                    />

4. dimension：尺寸值。

    （1）屬性定義：

            <declare-styleable name = "名稱">

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

            </declare-styleable>

    （2）屬性使用：

            <Button

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

                    />

5. float：浮點值。

    （1）屬性定義：

            <declare-styleable name = "AlphaAnimation">

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

            </declare-styleable>

    （2）屬性使用：

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

                   />

6. integer：整型值。

    （1）屬性定義：

            <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）屬性使用：

            <animated-rotate

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

                   />

7. string：字符串。

    （1）屬性定義：

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

    （2）屬性使用：

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

                    />

8. fraction：百分數。

    （1）屬性定義：

            <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）屬性使用：

            <rotate

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

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

                   android:pivotX = "200%"

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

                   android:repeatMode = "restart"

                   android:repeatCount = "infinite"

                   />

9. enum：枚舉值。

    （1）屬性定義：

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

            </declare-styleable>

    （2）屬性使用：

            <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：位或運算。

     （1）屬性定義：

             <declare-styleable name="名稱">
                    <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）屬性使用：

            <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>

特別要注意：

     屬性定義時能夠指定多種類型值。

    （1）屬性定義：

            <declare-styleable name = "名稱">

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

            </declare-styleable>

    （2）屬性使用：

             <ImageView

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

                     />

下面說說AttributeSet與TypedArray在自定義控件中的做用：

AttributeSet的做用就是在控件進行初始化的時候，解析佈局文件中該控件的屬性（key eg：background）與該值（value eg：@drawable/icon）的信息封裝在AttributeSet中，傳遞給該控件（View）的構造函數。對於非Android自帶的屬性，在View類中處理時是沒法識別的，所以須要咱們本身解析。因此這就要用到另一個類TypedArray。在AttributeSet中咱們有屬性名稱，有屬性值，可是控件如何知道哪一個屬性表明什麼意思呢？這個工做就由TypedArray來作了。TypedArray對象封裝了/values/attrs.xml中的styleable裏定義的每一個屬性的類型信息，經過TypedArray咱們就能夠知道AttributeSet中封裝的值究竟是幹什麼的了，從而能夠對這些數據進行應用。

AttributeSet就至關於一盒糖，TypedArray就至關於這盒糖上的標籤說明，告訴用戶每一個糖的口味等。這盒糖有什麼口味是由用戶本身的styleable文件裏面的內容來決定的。