EqualSizeLayout.java

package test.com.equalsizelayout;

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import java.util.HashMap;
import java.util.Map;

public final class EqualSizeLayout extends FrameLayout {

    private final Map<Integer, View> childById = new HashMap<>();

    public EqualSizeLayout(Context context) {
        super(context);
    }

    public EqualSizeLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public EqualSizeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public EqualSizeLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public void onViewAdded(View child) {
        super.onViewAdded(child);
        final int viewId = child.getId();
        if (viewId != View.NO_ID) {
            childById.put(viewId, child);
        }
    }

    @Override
    public void onViewRemoved(View child) {
        super.onViewRemoved(child);
        final int viewId = child.getId();
        if (viewId != View.NO_ID) {
            childById.remove(viewId);
        }
    }

    @Override
    protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
        super.measureChildWithMargins(child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
        if (child.getVisibility() == GONE) {
            return;
        }

        final LayoutParams lp = LayoutParams.class.cast(child.getLayoutParams());
        int height = -1;
        int width = -1;
        if (childById.containsKey(lp.equalHeightTo)) {
            height = childById.get(lp.equalHeightTo).getMeasuredHeight();
        }
        if (childById.containsKey(lp.equalWidthTo)) {
            width = childById.get(lp.equalWidthTo).getMeasuredWidth();
        }
        boolean changed = false;
        if (height > 0 && lp.height != height) {
            lp.height = height;
            changed = true;
        }
        if (width > 0 && lp.width != width) {
            lp.width = width;
            changed = true;
        }
        if (changed) {
            child.setLayoutParams(lp);
        }
    }

    @Override
    protected FrameLayout.LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(super.generateDefaultLayoutParams());
    }

    @Override
    protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
        return new LayoutParams(lp);
    }

    @Override
    public FrameLayout.LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new LayoutParams(getContext(), attrs);
    }

    public static final class LayoutParams extends FrameLayout.LayoutParams {

        private final int equalHeightTo;
        private final int equalWidthTo;

        private LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
            final TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.EqualSizeLayout_Layout);
            equalHeightTo = a.getResourceId(R.styleable.EqualSizeLayout_Layout_layout_equalHeightTo, 0);
            equalWidthTo = a.getResourceId(R.styleable.EqualSizeLayout_Layout_layout_equalWidthTo, 0);
            a.recycle();
        }

        public LayoutParams(int width, int height) {
            super(width, height);
            equalHeightTo = View.NO_ID;
            equalWidthTo = View.NO_ID;
        }

        public LayoutParams(int width, int height, int gravity) {
            super(width, height, gravity);
            equalHeightTo = View.NO_ID;
            equalWidthTo = View.NO_ID;
        }

        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
            equalHeightTo = View.NO_ID;
            equalWidthTo = View.NO_ID;
        }

        public LayoutParams(MarginLayoutParams source) {
            super(source);
            equalHeightTo = View.NO_ID;
            equalWidthTo = View.NO_ID;
        }

        public LayoutParams(FrameLayout.LayoutParams source) {
            super(source);
            equalHeightTo = View.NO_ID;
            equalWidthTo = View.NO_ID;
        }
    }
}