Android 深入理解Android中的自定义属性

1. 自定义一个CustomView(extends View )类

2. 编写values/attrs.xml，在其中编写styleable和item等标签元素

<!-- 一般写在attrs.xml文件中 -->
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="test"> <!-- name 可以随便写，但通常会与自定义控件类名相同，这样更直观 -->
        <attr name="text" format="string" />
        <attr name="testAttr" format="integer" />
    </declare-styleable>
</resources>

3. 在布局文件中CustomView使用自定义的属性（注意namespace）

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <com.example.test.MyTextView
        android:layout_width="100dp"
        android:layout_height="200dp"
        app:testAttr="520"
        app:text="helloworld" />
</RelativeLayout>

4. 在CustomView的构造方法中通过TypedArray获取

public MyTextView(Context context, AttributeSet attrs) {
        super(context, attrs);

        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.test);

        String text = ta.getString(R.styleable.test_testAttr);
        int textAttr = ta.getInteger(R.styleable.test_text, -1);

        Log.e(TAG, "text = " + text + " , textAttr = " + textAttr);

        ta.recycle();
    }

不过，作为模板代码，我觉得CirclePageIndicator的写法更好。

public CirclePageIndicator(Context context) {
        this(context, (AttributeSet)null);
    }

    public CirclePageIndicator(Context context, AttributeSet attrs) {
        this(context, attrs, attr.vpiCirclePageIndicatorStyle);
    }

    public CirclePageIndicator(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.mPaintPageFill = new Paint(1);
        this.mPaintStroke = new Paint(1);
        this.mPaintFill = new Paint(1);
        this.mLastMotionX = -1.0F;
        this.mActivePointerId = -1;
        if (!this.isInEditMode()) {
            // 先获取默认值
            Resources res = this.getResources();
            int defaultPageColor = res.getColor(color.default_circle_indicator_page_color);
            int defaultFillColor = Color.parseColor("#FF3964");
            int defaultOrientation = res.getInteger(integer.default_circle_indicator_orientation);
            int defaultStrokeColor = res.getColor(color.default_circle_indicator_stroke_color);
            float defaultStrokeWidth = res.getDimension(dimen.default_circle_indicator_stroke_width);
            float defaultRadius = res.getDimension(dimen.default_circle_indicator_radius);
            boolean defaultCentered = res.getBoolean(bool.default_circle_indicator_centered);
            boolean defaultSnap = res.getBoolean(bool.default_circle_indicator_snap);

            // 然后获取自定义属性在XML中的设置值
            TypedArray a = context.obtainStyledAttributes(attrs, styleable.CirclePageIndicator, defStyle, 0);
            this.mCentered = a.getBoolean(styleable.CirclePageIndicator_centered, defaultCentered);
            this.mOrientation = a.getInt(styleable.CirclePageIndicator_android_orientation, defaultOrientation);
            this.mPaintPageFill.setStyle(Style.FILL);
            this.mPaintPageFill.setColor(a.getColor(styleable.CirclePageIndicator_pageColor, defaultPageColor));
            this.mPaintStroke.setStyle(Style.STROKE);
            this.mPaintStroke.setColor(a.getColor(styleable.CirclePageIndicator_strokeColor, defaultStrokeColor));
            this.mPaintStroke.setStrokeWidth(a.getDimension(styleable.CirclePageIndicator_strokeWidth, defaultStrokeWidth));
            this.mPaintFill.setStyle(Style.FILL);
            this.mPaintFill.setColor(a.getColor(styleable.CirclePageIndicator_fillColor, defaultFillColor));
            this.mRadius = a.getDimension(styleable.CirclePageIndicator_radius, defaultRadius);
            this.mSnap = a.getBoolean(styleable.CirclePageIndicator_snap, defaultSnap);
            Drawable background = a.getDrawable(styleable.CirclePageIndicator_android_background);
            if (background != null) {
                this.setBackgroundDrawable(background);
            }

            // recycle
            a.recycle();
            ViewConfiguration configuration = ViewConfiguration.get(context);
            this.mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
        }
    }

5. 在style文件中使用自定义属性

https://blog.csdn.net/jiahongyu0529/article/details/78701490
https://blog.csdn.net/tomlucky1024/article/details/60877926

不需要加限定，直接使用

<style name="ScanUploading">
     <item name="android:background">@color/white</item>
     <item name="testAttr">"how do u do"</item>
</style>