AlbumLayoutManager.java

package info.guardianproject.pixelknot;

import android.content.Context;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.TypedValue;

class AlbumLayoutManager extends GridLayoutManager {

    private int mColumnWidth;
    private boolean mColumnWidthChanged = true;

    public AlbumLayoutManager(Context context, int columnWidth) {
        super(context, 1);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    public AlbumLayoutManager(Context context, int columnWidth, int orientation, boolean reverseLayout) {
    /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1, orientation, reverseLayout);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    private int checkedColumnWidth(Context context, int columnWidth) {
        if (columnWidth <= 0) {
        /* Set default columnWidth value (48dp here). It is better to move this constant
        to static constant on top, but we need context to convert it to dp, so can't really
        do so. */
            columnWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 48,
                    context.getResources().getDisplayMetrics());
        }
        return columnWidth;
    }

    public void setColumnWidth(int newColumnWidth) {
        if (newColumnWidth > 0 && newColumnWidth != mColumnWidth) {
            mColumnWidth = newColumnWidth;
            mColumnWidthChanged = true;
        }
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
        if (mColumnWidthChanged && mColumnWidth > 0) {
            int totalSpace;
            if (getOrientation() == VERTICAL) {
                totalSpace = getWidth() - getPaddingRight() - getPaddingLeft();
            } else {
                totalSpace = getHeight() - getPaddingTop() - getPaddingBottom();
            }
            int spanCount = Math.max(1, totalSpace / mColumnWidth);
            setSpanCount(spanCount);
            mColumnWidthChanged = false;
        }
        super.onLayoutChildren(recycler, state);
    }
}