FlowLayout.java

package io.evercam.androidapp.custom;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

/*
 * Container of views that it shows in a flow. If can not fit in a row, 
 * it will put the view in next line.
 */
public class FlowLayout extends ViewGroup
{
    private int lineHeight;

    public static class LayoutParams extends ViewGroup.LayoutParams
    {
        public final int horizontal_spacing;
        public final int vertical_spacing;

        /**
         * @param horizontal_spacing Pixels between items, horizontally
         * @param vertical_spacing   Pixels between items, vertically
         */
        public LayoutParams(int horizontal_spacing, int vertical_spacing)
        {
            super(0, 0);
            this.horizontal_spacing = horizontal_spacing;
            this.vertical_spacing = vertical_spacing;
        }
    }

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

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

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        assert (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.UNSPECIFIED);

        final int width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() -
                getPaddingRight();
        int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom();
        final int count = getChildCount();
        int lineHeight = 0;

        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();

        int childHeightMeasureSpec;
        if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST)
        {
            childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.AT_MOST);
        }
        else
        {
            childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
        }

        for(int i = 0; i < count; i++)
        {
            final View child = getChildAt(i);
            if(child.getVisibility() != GONE)
            {
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();
                child.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.AT_MOST),
                        childHeightMeasureSpec);
                final int childw = child.getMeasuredWidth();
                lineHeight = Math.max(lineHeight, child.getMeasuredHeight() + lp.vertical_spacing);

                if(xpos + childw > width)
                {
                    xpos = getPaddingLeft();
                    ypos += lineHeight;
                }

                xpos += childw + lp.horizontal_spacing;
            }
        }
        this.lineHeight = lineHeight;

        if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED)
        {
            height = ypos + lineHeight;

        }
        else if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST)
        {
            if(ypos + lineHeight < height)
            {
                height = ypos + lineHeight;
            }
        }
        setMeasuredDimension(width, height);
    }

    @Override
    protected ViewGroup.LayoutParams generateDefaultLayoutParams()
    {
        return new LayoutParams(1, 1); // default of 1px spacing
    }

    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p)
    {
        if(p instanceof LayoutParams)
        {
            return true;
        }
        return false;
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        final int count = getChildCount();
        final int width = r - l;
        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();

        for(int i = 0; i < count; i++)
        {
            final View child = getChildAt(i);
            if(child.getVisibility() != GONE)
            {
                final int childw = child.getMeasuredWidth();
                final int childh = child.getMeasuredHeight();
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();
                if(xpos + childw > width)
                {
                    xpos = getPaddingLeft();
                    ypos += lineHeight;
                }
                child.layout(xpos, ypos, xpos + childw, ypos + childh);
                xpos += childw + lp.horizontal_spacing;
            }
        }
    }
}