romannurik/DashboardLayout.java

## DashboardLayout.java
/*
 * ATTENTION:
 *
 * This layout is now maintained in the `iosched' code.google.com project:
 *
 * http://code.google.com/p/iosched/source/browse/android/src/com/google/android/apps/iosched/ui/widget/DashboardLayout.java
 *
 */

/*
 * Copyright 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.apps.iosched.ui.widget;

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

/**
 * Custom layout that arranges children in a grid-like manner, optimizing for even horizontal and
 * vertical whitespace.
 */
public class DashboardLayout extends ViewGroup {

    private static final int UNEVEN_GRID_PENALTY_MULTIPLIER = 10;

    private int mMaxChildWidth = 0;
    private int mMaxChildHeight = 0;

    public DashboardLayout(Context context) {
        super(context, null);
    }

    public DashboardLayout(Context context, AttributeSet attrs) {
        super(context, attrs, 0);
    }

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

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        mMaxChildWidth = 0;
        mMaxChildHeight = 0;

        final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
                MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);
        final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
                MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);

        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() == GONE) {
                continue;
            }

            child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

            mMaxChildWidth = Math.max(mMaxChildWidth, child.getMeasuredWidth());
            mMaxChildHeight = Math.max(mMaxChildHeight, child.getMeasuredHeight());
        }

        setMeasuredDimension(
                resolveSize(mMaxChildWidth, widthMeasureSpec),
                resolveSize(mMaxChildHeight, heightMeasureSpec));
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int width = r - l;
        int height = b - t;

        final int count = getChildCount();

        // Calculate the number of visible children.
        int visibleCount = 0;
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() == GONE) {
                continue;
            }
            ++visibleCount;
        }

        if (visibleCount == 0) {
            return;
        }

        // Calculate what number of rows and columns will optimize for even horizontal and
        // vertical whitespace between items. Start with a 1 x N grid, then try 2 x N, and so on.
        int bestSpaceDifference = Integer.MAX_VALUE;
        int spaceDifference;

        // Horizontal and vertical space between items
        int hSpace = 0;
        int vSpace = 0;

        int cols = 1;
        int rows;

        while (true) {
            rows = (visibleCount - 1) / cols + 1;

            hSpace = ((width - mMaxChildWidth * cols) / (cols + 1));
            vSpace = ((height - mMaxChildHeight * rows) / (rows + 1));

            spaceDifference = Math.abs(vSpace - hSpace);
            if (rows * cols != visibleCount) {
                spaceDifference *= UNEVEN_GRID_PENALTY_MULTIPLIER;
            }

            if (spaceDifference < bestSpaceDifference) {
                // Found a better whitespace squareness/ratio
                bestSpaceDifference = spaceDifference;

                // If we found a better whitespace squareness and there's only 1 row, this is
                // the best we can do.
                if (rows == 1) {
                    break;
                }
            } else {
                // This is a worse whitespace ratio, use the previous value of cols and exit.
                --cols;
                rows = (visibleCount - 1) / cols + 1;
                hSpace = ((width - mMaxChildWidth * cols) / (cols + 1));
                vSpace = ((height - mMaxChildHeight * rows) / (rows + 1));
                break;
            }

            ++cols;
        }

        // Lay out children based on calculated best-fit number of rows and cols.

        // If we chose a layout that has negative horizontal or vertical space, force it to zero.
        hSpace = Math.max(0, hSpace);
        vSpace = Math.max(0, vSpace);

        // Re-use width/height variables to be child width/height.
        width = (width - hSpace * (cols + 1)) / cols;
        height = (height - vSpace * (rows + 1)) / rows;

        int left, top;
        int col, row;
        int visibleIndex = 0;
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() == GONE) {
                continue;
            }

            row = visibleIndex / cols;
            col = visibleIndex % cols;

            left = l + hSpace * (col + 1) + width * col;
            top = t + vSpace * (row + 1) + height * row;

            child.layout(left, top,
                    (hSpace == 0 && col == cols - 1) ? r : (left + width),
                    (vSpace == 0 && row == rows - 1) ? b : (top + height));
            ++visibleIndex;
        }
    }
}
	/*
	* ATTENTION:
	*
	* This layout is now maintained in the `iosched' code.google.com project:
	*
	* http://code.google.com/p/iosched/source/browse/android/src/com/google/android/apps/iosched/ui/widget/DashboardLayout.java
	*
	*/

	/*
	* Copyright 2011 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.google.android.apps.iosched.ui.widget;

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

	/**
	* Custom layout that arranges children in a grid-like manner, optimizing for even horizontal and
	* vertical whitespace.
	*/
	public class DashboardLayout extends ViewGroup {

	private static final int UNEVEN_GRID_PENALTY_MULTIPLIER = 10;

	private int mMaxChildWidth = 0;
	private int mMaxChildHeight = 0;

	public DashboardLayout(Context context) {
	super(context, null);
	}

	public DashboardLayout(Context context, AttributeSet attrs) {
	super(context, attrs, 0);
	}

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

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
	mMaxChildWidth = 0;
	mMaxChildHeight = 0;

	final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
	MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);
	final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
	MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);

	final int count = getChildCount();
	for (int i = 0; i < count; i++) {
	final View child = getChildAt(i);
	if (child.getVisibility() == GONE) {
	continue;
	}

	child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

	mMaxChildWidth = Math.max(mMaxChildWidth, child.getMeasuredWidth());
	mMaxChildHeight = Math.max(mMaxChildHeight, child.getMeasuredHeight());
	}

	setMeasuredDimension(
	resolveSize(mMaxChildWidth, widthMeasureSpec),
	resolveSize(mMaxChildHeight, heightMeasureSpec));
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
	int width = r - l;
	int height = b - t;

	final int count = getChildCount();

	// Calculate the number of visible children.
	int visibleCount = 0;
	for (int i = 0; i < count; i++) {
	final View child = getChildAt(i);
	if (child.getVisibility() == GONE) {
	continue;
	}
	++visibleCount;
	}

	if (visibleCount == 0) {
	return;
	}

	// Calculate what number of rows and columns will optimize for even horizontal and
	// vertical whitespace between items. Start with a 1 x N grid, then try 2 x N, and so on.
	int bestSpaceDifference = Integer.MAX_VALUE;
	int spaceDifference;

	// Horizontal and vertical space between items
	int hSpace = 0;
	int vSpace = 0;

	int cols = 1;
	int rows;

	while (true) {
	rows = (visibleCount - 1) / cols + 1;

	hSpace = ((width - mMaxChildWidth * cols) / (cols + 1));
	vSpace = ((height - mMaxChildHeight * rows) / (rows + 1));

	spaceDifference = Math.abs(vSpace - hSpace);
	if (rows * cols != visibleCount) {
	spaceDifference *= UNEVEN_GRID_PENALTY_MULTIPLIER;
	}

	if (spaceDifference < bestSpaceDifference) {
	// Found a better whitespace squareness/ratio
	bestSpaceDifference = spaceDifference;

	// If we found a better whitespace squareness and there's only 1 row, this is
	// the best we can do.
	if (rows == 1) {
	break;
	}
	} else {
	// This is a worse whitespace ratio, use the previous value of cols and exit.
	--cols;
	rows = (visibleCount - 1) / cols + 1;
	hSpace = ((width - mMaxChildWidth * cols) / (cols + 1));
	vSpace = ((height - mMaxChildHeight * rows) / (rows + 1));
	break;
	}

	++cols;
	}

	// Lay out children based on calculated best-fit number of rows and cols.

	// If we chose a layout that has negative horizontal or vertical space, force it to zero.
	hSpace = Math.max(0, hSpace);
	vSpace = Math.max(0, vSpace);

	// Re-use width/height variables to be child width/height.
	width = (width - hSpace * (cols + 1)) / cols;
	height = (height - vSpace * (rows + 1)) / rows;

	int left, top;
	int col, row;
	int visibleIndex = 0;
	for (int i = 0; i < count; i++) {
	final View child = getChildAt(i);
	if (child.getVisibility() == GONE) {
	continue;
	}

	row = visibleIndex / cols;
	col = visibleIndex % cols;

	left = l + hSpace * (col + 1) + width * col;
	top = t + vSpace * (row + 1) + height * row;

	child.layout(left, top,
	(hSpace == 0 && col == cols - 1) ? r : (left + width),
	(vSpace == 0 && row == rows - 1) ? b : (top + height));
	++visibleIndex;
	}
	}
	}