为FrameLayout的子级设置center_horizo​​ntal

Question

在下面的这段代码中，我想将center_horizo​​ntal设置为attachmentSlidingLayer的视图ID，但是父视图和子视图的layout_gravity和gravity不能正常工作，默认情况下重力为左侧< / p>

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:slidingLayer="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <io.codetail.widget.RevealFrameLayout  <!-- extends from FrameLayout -->
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center_horizontal">

        <com.test.libraries.SlidingLayer  <!-- extends from BoundedFrameLayout-->
            android:id="@+id/attachmentSlidingLayer"
            android:layout_width="match_parent"
            android:layout_height="210dp"
            android:layout_gravity="center_horizontal"
            android:elevation="5dp"
            app:bounded_width="450dp"
            android:foregroundGravity="center_horizontal">

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_gravity="center_horizontal"
                    android:gravity="center_horizontal"
                    android:background="@drawable/sheet_shadow"
                    android:orientation="vertical"
                    app:bounded_width="450dp">
                </LinearLayout>
        </<com.test.libraries.SlidingLayer.SlidingLayer >

    </io.codetail.widget.RevealFrameLayout>

</android.support.design.widget.CoordinatorLayout>

BoundedFrameLayout类：

public class BoundedFrameLayout extends FrameLayout {

    private final int mBoundedWidth;

    private final int mBoundedHeight;

    public BoundedFrameLayout(Context context) {
        super(context);
        mBoundedWidth = 0;
        mBoundedHeight = 0;
    }

    public BoundedFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BoundedView);
        mBoundedWidth = a.getDimensionPixelSize(R.styleable.BoundedView_bounded_width, 0);
        mBoundedHeight = a.getDimensionPixelSize(R.styleable.BoundedView_bounded_height, 0);
        a.recycle();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // Adjust width as necessary
        int measuredWidth = MeasureSpec.getSize(widthMeasureSpec);
        if (mBoundedWidth > 0 && mBoundedWidth < measuredWidth) {
            int measureMode = MeasureSpec.getMode(widthMeasureSpec);
            widthMeasureSpec = MeasureSpec.makeMeasureSpec(mBoundedWidth, measureMode);
        }
        // Adjust height as necessary
        int measuredHeight = MeasureSpec.getSize(heightMeasureSpec);
        if (mBoundedHeight > 0 && mBoundedHeight < measuredHeight) {
            int measureMode = MeasureSpec.getMode(heightMeasureSpec);
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(mBoundedHeight, measureMode);
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
}

RevealFrameLayout类：

public class RevealFrameLayout extends FrameLayout implements RevealAnimator{

    private Path mRevealPath;
    private final Rect mTargetBounds = new Rect();
    private RevealInfo mRevealInfo;
    private boolean mRunning;
    private float mRadius;

    public RevealFrameLayout(Context context) {
        this(context, null);
    }

    public RevealFrameLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public RevealFrameLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mRevealPath = new Path();
    }

    @Override
    public void onRevealAnimationStart() {
        mRunning = true;
    }

    @Override
    public void onRevealAnimationEnd() {
        mRunning = false;
        invalidate(mTargetBounds);
    }

    @Override
    public void onRevealAnimationCancel() {
        onRevealAnimationEnd();
    }

    @Override
    public void setRevealRadius(float radius){
        mRadius = radius;
        mRevealInfo.getTarget().getHitRect(mTargetBounds);
        invalidate(mTargetBounds);
    }

    @Override
    public float getRevealRadius(){
        return mRadius;
    }

    @Override
    public void attachRevealInfo(RevealInfo info) {
        mRevealInfo = info;
    }

    @Override
    public SupportAnimator startReverseAnimation() {
        if(mRevealInfo != null && mRevealInfo.hasTarget() && !mRunning) {
            return ViewAnimationUtils.createCircularReveal(mRevealInfo.getTarget(),
                    mRevealInfo.centerX, mRevealInfo.centerY,
                    mRevealInfo.endRadius, mRevealInfo.startRadius);
        }
        return null;
    }

    @Override
    protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
        if(mRunning && child == mRevealInfo.getTarget()){
            final int state = canvas.save();
            mRevealPath.reset();
            mRevealPath.addCircle(mRevealInfo.centerX, mRevealInfo.centerY, mRadius, Path.Direction.CW);
            canvas.clipPath(mRevealPath);
            boolean isInvalided = super.drawChild(canvas, child, drawingTime);
            canvas.restoreToCount(state);
            return isInvalided;
        }
        return super.drawChild(canvas, child, drawingTime);
    }
}