root/chrome/android/java/src/org/chromium/chrome/browser/appmenu/AppMenu.java

DEFINITIONS

1. show
2. setPopupOffset
3. onItemClick
4. onItemClick
5. dismiss
6. isShowing
7. getPopup
8. setMenuHeight

// Copyright 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package org.chromium.chrome.browser.appmenu;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Rect;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.Surface;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageButton;
import android.widget.ListPopupWindow;
import android.widget.PopupWindow;
import android.widget.PopupWindow.OnDismissListener;

import org.chromium.chrome.R;

import java.util.ArrayList;
import java.util.List;

/**
 * Shows a popup of menuitems anchored to a host view. When a item is selected we call
 * Activity.onOptionsItemSelected with the appropriate MenuItem.
 *   - Only visible MenuItems are shown.
 *   - Disabled items are grayed out.
 */
public class AppMenu implements OnItemClickListener {
    private static final float LAST_ITEM_SHOW_FRACTION = 0.5f;
    private static final int DIVIDER_HEIGHT_DP = 1;

    private final Menu mMenu;
    private final int mItemRowHeight;
    private final int mItemDividerHeight;
    private final int mVerticalFadeDistance;
    private final int mAdditionalVerticalOffset;
    private ListPopupWindow mPopup;
    private AppMenuAdapter mAdapter;
    private AppMenuHandler mHandler;
    private int mCurrentScreenRotation = -1;
    private boolean mIsByHardwareButton;

    /**
     * Creates and sets up the App Menu.
     * @param menu Original menu created by the framework.
     * @param itemRowHeight Desired height for each app menu row.
     * @param handler AppMenuHandler receives callbacks from AppMenu.
     * @param res Resources object used to get dimensions and style attributes.
     */
    AppMenu(Menu menu, int itemRowHeight, AppMenuHandler handler, Resources res) {
        mMenu = menu;

        mItemRowHeight = itemRowHeight;
        assert mItemRowHeight > 0;

        mHandler = handler;

        final float dpToPx = res.getDisplayMetrics().density;
        mItemDividerHeight = Math.round(DIVIDER_HEIGHT_DP * dpToPx);

        mAdditionalVerticalOffset = res.getDimensionPixelSize(R.dimen.menu_vertical_offset);
        mVerticalFadeDistance = res.getDimensionPixelSize(R.dimen.menu_vertical_fade_distance);
    }

    /**
     * Creates and shows the app menu anchored to the specified view.
     *
     * @param context             The context of the AppMenu (ensure the proper theme is set on
     *                            this context).
     * @param anchorView          The anchor {@link View} of the {@link ListPopupWindow}.
     * @param isByHardwareButton  Whether or not hardware button triggered it. (oppose to software
     *                            button)
     * @param screenRotation      Current device screen rotation.
     * @param visibleDisplayFrame The display area rect in which AppMenu is supposed to fit in.
     */
    void show(Context context, View anchorView, boolean isByHardwareButton, int screenRotation,
            Rect visibleDisplayFrame) {
        mPopup = new ListPopupWindow(context, null, android.R.attr.popupMenuStyle);
        mPopup.setModal(true);
        mPopup.setAnchorView(anchorView);
        mPopup.setInputMethodMode(PopupWindow.INPUT_METHOD_NOT_NEEDED);
        mPopup.setOnDismissListener(new OnDismissListener() {
            @Override
            public void onDismiss() {
                if (mPopup.getAnchorView() instanceof ImageButton) {
                    ((ImageButton) mPopup.getAnchorView()).setSelected(false);
                }
                mHandler.onMenuVisibilityChanged(false);
            }
        });
        mPopup.setWidth(context.getResources().getDimensionPixelSize(R.dimen.menu_width));

        mCurrentScreenRotation = screenRotation;
        mIsByHardwareButton = isByHardwareButton;

        // Extract visible items from the Menu.
        int numItems = mMenu.size();
        List<MenuItem> menuItems = new ArrayList<MenuItem>();
        for (int i = 0; i < numItems; ++i) {
            MenuItem item = mMenu.getItem(i);
            if (item.isVisible()) {
                menuItems.add(item);
            }
        }

        // A List adapter for visible items in the Menu. The first row is added as a header to the
        // list view.
        mAdapter = new AppMenuAdapter(this, menuItems, LayoutInflater.from(context));
        mPopup.setAdapter(mAdapter);

        setMenuHeight(menuItems.size(), visibleDisplayFrame);
        setPopupOffset(mPopup, mCurrentScreenRotation, visibleDisplayFrame);
        mPopup.setOnItemClickListener(this);
        mPopup.show();
        mPopup.getListView().setDividerHeight(mItemDividerHeight);
        mPopup.getListView().setItemsCanFocus(true);

        mHandler.onMenuVisibilityChanged(true);

        if (mVerticalFadeDistance > 0) {
            mPopup.getListView().setVerticalFadingEdgeEnabled(true);
            mPopup.getListView().setFadingEdgeLength(mVerticalFadeDistance);
        }
    }

    private void setPopupOffset(ListPopupWindow popup, int screenRotation, Rect appRect) {
        Rect paddingRect = new Rect();
        popup.getBackground().getPadding(paddingRect);
        int[] anchorLocation = new int[2];
        popup.getAnchorView().getLocationInWindow(anchorLocation);

        // If we have a hardware menu button, locate the app menu closer to the estimated
        // hardware menu button location.
        if (mIsByHardwareButton) {
            int horizontalOffset = -anchorLocation[0];
            switch (screenRotation) {
                case Surface.ROTATION_0:
                case Surface.ROTATION_180:
                    horizontalOffset += (appRect.width() - mPopup.getWidth()) / 2;
                    break;
                case Surface.ROTATION_90:
                    horizontalOffset += appRect.width() - mPopup.getWidth();
                    break;
                case Surface.ROTATION_270:
                    break;
                default:
                    assert false;
                    break;
            }
            popup.setHorizontalOffset(horizontalOffset);
            // The menu is displayed above the anchored view, so shift the menu up by the top
            // padding of the background.
            popup.setVerticalOffset(mAdditionalVerticalOffset - paddingRect.bottom);
        } else {
            // The menu is displayed below the anchored view, so shift the menu up by the top
            // padding of the background.
            popup.setVerticalOffset(mAdditionalVerticalOffset - paddingRect.top);
        }
    }

    /**
     * Handles clicks on the AppMenu popup.
     * @param menuItem The menu item in the popup that was clicked.
     */
    void onItemClick(MenuItem menuItem) {
        if (menuItem.isEnabled()) {
            dismiss();
            mHandler.onOptionsItemSelected(menuItem);
        }
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        onItemClick(mAdapter.getItem(position));
    }

    /**
     * Dismisses the app menu and cancels the drag-to-scroll if it is taking place.
     */
    void dismiss() {
        mHandler.appMenuDismissed();
        if (isShowing()) mPopup.dismiss();
    }

    /**
     * @return Whether the app menu is currently showing.
     */
    boolean isShowing() {
        if (mPopup == null) {
            return false;
        }
        return mPopup.isShowing();
    }

    /**
     * @return ListPopupWindow that displays all the menu options.
     */
    ListPopupWindow getPopup() {
        return mPopup;
    }

    private void setMenuHeight(int numMenuItems, Rect appDimensions) {
        assert mPopup.getAnchorView() != null;
        View anchorView = mPopup.getAnchorView();
        int[] anchorViewLocation = new int[2];
        anchorView.getLocationOnScreen(anchorViewLocation);
        anchorViewLocation[1] -= appDimensions.top;

        int availableScreenSpace = Math.max(anchorViewLocation[1],
                appDimensions.height() - anchorViewLocation[1] - anchorView.getHeight());

        Rect padding = new Rect();
        mPopup.getBackground().getPadding(padding);
        availableScreenSpace -= mIsByHardwareButton ? padding.top : padding.bottom;

        int numCanFit = availableScreenSpace / (mItemRowHeight + mItemDividerHeight);

        // Fade out the last item if we cannot fit all items.
        if (numCanFit < numMenuItems) {
            int spaceForFullItems = numCanFit * (mItemRowHeight + mItemDividerHeight);
            int spaceForPartialItem = (int) (LAST_ITEM_SHOW_FRACTION * mItemRowHeight);
            // Determine which item needs hiding.
            if (spaceForFullItems + spaceForPartialItem < availableScreenSpace) {
                mPopup.setHeight(spaceForFullItems + spaceForPartialItem +
                        padding.top + padding.bottom);
            } else {
                mPopup.setHeight(spaceForFullItems - mItemRowHeight + spaceForPartialItem +
                        padding.top + padding.bottom);
            }
        } else {
            mPopup.setHeight(ViewGroup.LayoutParams.WRAP_CONTENT);
        }
    }