MaxWidthFrameLayout.java

package com.abewy.android.extended.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import com.abewy.android.extended.R;

/**
* A simple {@link LinearLayout} subclass, useful only in the vertical orientation, that allows each
* child to define a maximum width using a {@link LayoutParams#maxWidth layout_maxWidth} attribute
* (only useful if the child's {@link ViewGroup.LayoutParams#width layout_width} is {@link
* ViewGroup.LayoutParams#MATCH_PARENT}).
*/
public class MaxWidthFrameLayout extends FrameLayout
{
	public MaxWidthFrameLayout(Context context)
	{
		super(context);
	}

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

	public MaxWidthFrameLayout(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
	}

	/**
	* Temporarily assign a new {@link ViewGroup.LayoutParams#width} to the maximum width if the
	* child would normally exceed the maximum width.
	*/
	private void assignTemporaryChildWidthDuringMeasure(View child, int parentWidthMeasureSpec)
	{
		LayoutParams lp = (LayoutParams) child.getLayoutParams();
		assert lp != null;
		int availableWidth = MeasureSpec.getSize(parentWidthMeasureSpec);
		if (lp.width == LayoutParams.MATCH_PARENT && availableWidth > lp.maxWidth)
		{
			lp.oldLayoutWidth = LayoutParams.MATCH_PARENT;
			lp.width = Math.min(lp.maxWidth, availableWidth);
		}
	}

	/**
	* Revert any changes caused by {@link #assignTemporaryChildWidthDuringMeasure(android.view.View,
	* int)}.
	*/
	private void revertChildWidthDuringMeasure(View child)
	{
		LayoutParams lp = (LayoutParams) child.getLayoutParams();
		assert lp != null;
		if (lp.oldLayoutWidth != Integer.MIN_VALUE)
		{
			lp.width = lp.oldLayoutWidth;
		}
	}

	@Override
	protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec)
	{
		assignTemporaryChildWidthDuringMeasure(child, parentWidthMeasureSpec);
		super.measureChild(child, parentWidthMeasureSpec, parentHeightMeasureSpec);
		revertChildWidthDuringMeasure(child);
	}

	@Override
	protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed)
	{
		assignTemporaryChildWidthDuringMeasure(child, parentWidthMeasureSpec);
		super.measureChildWithMargins(child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
		revertChildWidthDuringMeasure(child);
	}

	@Override
	protected MaxWidthFrameLayout.LayoutParams generateDefaultLayoutParams()
	{
		return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
	}

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

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

	@Override
	protected boolean checkLayoutParams(ViewGroup.LayoutParams lp)
	{
		return lp instanceof MaxWidthFrameLayout.LayoutParams;
	}

	/**
	* Provides additional layout params (specifically {@link #maxWidth layout_maxWidth}) for
	* children of {@link MaxWidthFrameLayout}.
	*/
	public static class LayoutParams extends FrameLayout.LayoutParams
	{
		private int	maxWidth;
		private int	oldLayoutWidth	= Integer.MIN_VALUE;	// used to store old lp.width during measure

		public LayoutParams(Context c, AttributeSet attrs)
		{
			super(c, attrs);

			TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.MaxWidthLinearLayout_Layout);
			assert a != null;
			maxWidth = a.getLayoutDimension(R.styleable.MaxWidthLinearLayout_Layout_layout_maxWidth, Integer.MAX_VALUE);
		}

		public LayoutParams(int width, int height)
		{
			super(width, height);
		}

		public LayoutParams(int width, int height, int gravity)
		{
			super(width, height, gravity);
		}

		public LayoutParams(ViewGroup.LayoutParams source)
		{
			super(source);
		}

		public LayoutParams(MarginLayoutParams source)
		{
			super(source);
		}
	}
}