java - 如何通过反射从 declare styleable TypedArray 获取值？

Question

我正在使用形状 ImageView (https://github.com/siyamed/android-shape-imageview)，当我想从形状 ImageView 定义的 declare-styleable 中获取值时:

<declare-styleable name="ShaderImageView">
    <attr name="siSquare" format="boolean" />
    <attr name="siBorderColor" format="color" />
    <attr name="siBorderWidth" format="dimension" />
    <attr name="siBorderAlpha" format="float" />
    <attr name="siForeground" format="integer|reference" />
    <!--  Rounded Image View-->
    <attr name="siRadius" format="dimension" />
    <!-- BubbleImageView-->
    <attr name="siArrowPosition" />
    <attr name="siTriangleHeight" format="dimension" />
    <!-- PorterImageView-->
    <attr name="siShape" format="integer|reference" />
    <!-- ShaderImageView-->
    <attr name="siBorderType" />
    <attr name="siStrokeCap" />
    <attr name="siStrokeJoin" />
    <attr name="siStrokeMiter" format="dimension" />
</declare-styleable>
<attr name="siArrowPosition">
    <enum name="left" value="0" />
    <enum name="right" value="1" />
</attr>
<attr name="siBorderType">
    <enum name="stroke" value="0" />
    <enum name="fill" value="1" />
</attr>
<attr name="siStrokeCap">
    <enum name="butt" value="0" />
    <enum name="round" value="1" />
    <enum name="square" value="2" />
</attr>
<attr name="siStrokeJoin">
    <enum name="bevel" value="0" />
    <enum name="miter" value="1" />
    <enum name="round" value="2" />
</attr>

我有问题。我的形状 ImageView 的 xml 用法:

<com.demo.example.BubbleImageView
            android:id="@+id/picture_iv"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:siArrowPosition="right"
            android:layout_gravity="center"
            app:siBorderWidth="@dimen/default_border_width"
            app:siRadius="5dp"
            android:src="@drawable/fetch_failed"/>

这是我的代码:

public void init(Context context, AttributeSet attrs, int defStyle) {
    if(attrs != null){
        int[] declareStyleableArray = IdHelper.getResourceDeclareStyleableIntArray(context, "ShaderImageView");
        if (declareStyleableArray != null && declareStyleableArray.length > 0) {
            TypedArray typedArray = context.obtainStyledAttributes(attrs, declareStyleableArray, defStyle, 0);
            square = typedArray.getBoolean(IdHelper.getAttr(context, "ShaderImageView_siSquare"), square);
            borderColor = typedArray.getColor(IdHelper.getAttr(context, "ShaderImageView_siBorderColor"), borderColor);
            borderWidth = typedArray.getDimensionPixelSize(IdHelper.getAttr(context, "ShaderImageView_siBorderWidth"), borderWidth);
            borderAlpha = typedArray.getFloat(IdHelper.getAttr(context, "ShaderImageView_siBorderAlpha"), borderAlpha);
            typedArray.recycle();
        }

    }

IdHelper中定义的方法:

public static int[] getResourceDeclareStyleableIntArray(Context context, String name) {
    try {
        //use reflection to access the resource class
        Field[] fields2 = Class.forName(context.getPackageName() + ".R$styleable").getFields();

        //browse all fields
        for (Field f : fields2) {
            //pick matching field
            if (f.getName().equals(name)) {
                //return as int array
                return (int[]) f.get(null);
            }
        }
    } catch (Throwable t) {
        t.printStackTrace();
    }

    return null;
}
public static int getAttr(Context context, String attrName) {
    return context.getResources().getIdentifier(attrName, "attr",
            context.getApplicationContext().getPackageName());
}

当我运行我的应用程序时，我得到了日志:

01-11 17:04:07.244 3744-3744/? W/System.err: Caused by: java.lang.reflect.InvocationTargetException 01-11 17:04:07.247 3744-3744/? W/System.err: at java.lang.reflect.Constructor.constructNative(Native Method) 01-11 17:04:07.247 3744-3744/? W/System.err: at java.lang.reflect.Constructor.newInstance(Constructor.java:423) 01-11 17:04:07.247 3744-3744/? W/System.err: at android.view.LayoutInflater.createView(LayoutInflater.java:594) 01-11 17:04:07.247 3744-3744/? W/System.err: ... 57 more 01-11 17:04:07.247 3744-3744/? W/System.err: Caused by: java.lang.UnsupportedOperationException: Can't convert to dimension: type=0x10 01-11 17:04:07.252 3744-3744/? W/System.err: at android.content.res.TypedArray.getDimensionPixelSize(TypedArray.java:464) 01-11 17:04:07.252 3744-3744/? W/System.err: at cn.jmessage.android.uikit.chatting.shader.ShaderHelper.init(ShaderHelper.java:80) 01-11 17:04:07.252 3744-3744/? W/System.err: at cn.jmessage.android.uikit.chatting.shader.BubbleShader.init(BubbleShader.java:45) 01-11 17:04:07.253 3744-3744/? W/System.err: at cn.jmessage.android.uikit.chatting.ShaderImageView.setup(ShaderImageView.java:45) 01-11 17:04:07.253 3744-3744/? W/System.err: at cn.jmessage.android.uikit.chatting.ShaderImageView.(ShaderImageView.java:36) 01-11 17:04:07.253 3744-3744/? W/System.err: at cn.jmessage.android.uikit.chatting.BubbleImageView.(BubbleImageView.java:27) 01-11 17:04:07.253 3744-3744/? W/System.err: ... 60 more

我该如何解决这个问题？

Answer 1

我已经解决了这个问题。您在 attrs 文件中定义的 declare-styleable 属性，解析后，将在 R 文件中生成一个 int 数组。在我的例子中，数组是这样的:

       @see #ShaderImageView_siArrowPosition
       @see #ShaderImageView_siBorderAlpha
       @see #ShaderImageView_siBorderColor
       @see #ShaderImageView_siBorderType
       @see #ShaderImageView_siBorderWidth
       @see #ShaderImageView_siForeground
       @see #ShaderImageView_siRadius
       @see #ShaderImageView_siShape
       @see #ShaderImageView_siSquare
       @see #ShaderImageView_siStrokeCap
       @see #ShaderImageView_siStrokeJoin
       @see #ShaderImageView_siStrokeMiter
       @see #ShaderImageView_siTriangleHeight
     */
    public static final int[] ShaderImageView = {
        0x7f010001, 0x7f010002, 0x7f010003, 0x7f010004,
        0x7f01000c, 0x7f01000d, 0x7f01000e, 0x7f01000f,
        0x7f010010, 0x7f010011, 0x7f010012, 0x7f010013,
        0x7f010014
    };

注意这个数组的顺序，是按照字母升序排列的，所以我可以这样获取属性值:

public void init(Context context, AttributeSet attrs, int defStyle) {
    if(attrs != null){
        int[] declareStyleableArray = IdHelper.getResourceDeclareStyleableIntArray(context, "ShaderImageView");
        if (declareStyleableArray != null && declareStyleableArray.length > 0) {
            TypedArray typedArray = context.obtainStyledAttributes(attrs, declareStyleableArray, defStyle, 0);
            square = typedArray.getBoolean(8, square);
            borderColor = typedArray.getColor(2, borderColor);
            borderWidth = typedArray.getDimensionPixelSize(4, borderWidth);
            borderAlpha = typedArray.getFloat(1, borderAlpha);
            typedArray.recycle();
        }

    }

注意这一行:square = typedArray.getBoolean(8, square);第一个参数是8，这是R文件中生成的数组ShaderImageView中属性“ShaderImageView_siSquare”的顺序。这意味着如果您在 attrs 文件中定义自定义 declare-styleable 集，您定义的顺序可能与解析后在 R 文件中生成的顺序不同，如果您使用 R 获取属性值，例如:

square = typedArray.getBoolean(R.styleable.ShaderImageView_siSquare, square);

那么顺序就不用管了。希望我的案例对某人有所帮助。