DisplayUtils.java

/*
Yaaic - Yet Another Android IRC Client

Copyright 2009-2013 Sebastian Kaspari

This file is part of Yaaic.

Yaaic is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Yaaic is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Yaaic.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.numixproject.hermes.utils;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.ListView;

/**
 * Helper class for methods regarding the display of the current device.
 *
 * @author Sebastian Kaspari <sebastian@yaaic.org>
 */
public class DisplayUtils
{
    private static float density = -1;

    public static void setListViewHeightBasedOnChildren(ListView listView) {
        ListAdapter listAdapter = listView.getAdapter();
        if (listAdapter == null) {
            // pre-condition
            return;
        }

        int totalHeight = 0;
        int desiredWidth = View.MeasureSpec.makeMeasureSpec(listView.getWidth(), View.MeasureSpec.AT_MOST);
        for (int i = 0; i < listAdapter.getCount(); i++) {
            View listItem = listAdapter.getView(i, null, listView);
            listItem.measure(desiredWidth, View.MeasureSpec.UNSPECIFIED);
            totalHeight += listItem.getMeasuredHeight();
        }

        ViewGroup.LayoutParams params = listView.getLayoutParams();
        params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
        listView.setLayoutParams(params);
        listView.requestLayout();
    }

    /**
     * Convert the given density-independent pixels into real pixels for the
     * display of the device.
     *
     * @param dp
     * @return
     */
    public static int convertToPixels(Context context, int dp) {
        float density = getScreenDensity(context);

        return (int) (dp * density + 0.5f);
    }

    /**
     * Get the density of the display of the device.
     *
     * @param context
     * @return
     */
    public static float getScreenDensity(Context context) {
        if (density == -1) {
            density = context.getResources().getDisplayMetrics().density;
        }

        return density;
    }
}