Java tutorial
/* * Copyright (C) 2016 The Android Open Source Project * * 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 android.support.v7.view.menu; import android.content.Context; import android.graphics.Rect; import android.support.annotation.NonNull; import android.support.annotation.Nullable; import android.support.v4.internal.view.SupportMenu; import android.view.MenuItem; import android.view.View; import android.view.View.MeasureSpec; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.FrameLayout; import android.widget.HeaderViewListAdapter; import android.widget.ListAdapter; import android.widget.PopupWindow; /** * Base class for a menu popup abstraction - i.e., some type of menu, housed in a popup window * environment. */ abstract class MenuPopup implements ShowableListMenu, MenuPresenter, AdapterView.OnItemClickListener { private Rect mEpicenterBounds; public abstract void setForceShowIcon(boolean forceShow); /** * Adds the given menu to the popup, if it is capable of displaying submenus within itself. * If menu is the first menu shown, it won't be displayed until show() is called. * If the popup was already showing, adding a submenu via this method will cause that new * submenu to be shown immediately (that is, if this MenuPopup implementation is capable of * showing its own submenus). * * @param menu */ public abstract void addMenu(MenuBuilder menu); public abstract void setGravity(int dropDownGravity); public abstract void setAnchorView(View anchor); public abstract void setHorizontalOffset(int x); public abstract void setVerticalOffset(int y); /** * Specifies the anchor-relative bounds of the popup's transition * epicenter. * * @param bounds anchor-relative bounds */ public void setEpicenterBounds(Rect bounds) { mEpicenterBounds = bounds; } /** * @return anchor-relative bounds of the popup's transition epicenter */ public Rect getEpicenterBounds() { return mEpicenterBounds; } /** * Set whether a title entry should be shown in the popup menu (if a title exists for the * menu). * * @param showTitle */ public abstract void setShowTitle(boolean showTitle); /** * Set a listener to receive a callback when the popup is dismissed. * * @param listener Listener that will be notified when the popup is dismissed. */ public abstract void setOnDismissListener(PopupWindow.OnDismissListener listener); @Override public void initForMenu(@NonNull Context context, @Nullable MenuBuilder menu) { // Don't need to do anything; we added as a presenter in the constructor. } @Override public MenuView getMenuView(ViewGroup root) { throw new UnsupportedOperationException("MenuPopups manage their own views"); } @Override public boolean expandItemActionView(MenuBuilder menu, MenuItemImpl item) { return false; } @Override public boolean collapseItemActionView(MenuBuilder menu, MenuItemImpl item) { return false; } @Override public int getId() { return 0; } @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { ListAdapter outerAdapter = (ListAdapter) parent.getAdapter(); MenuAdapter wrappedAdapter = toMenuAdapter(outerAdapter); // Use the position from the outer adapter so that if a header view was added, we don't get // an off-by-1 error in position. wrappedAdapter.mAdapterMenu.performItemAction((MenuItem) outerAdapter.getItem(position), this, // always make sure that we show the sub-menu closeMenuOnSubMenuOpened() ? 0 : SupportMenu.FLAG_KEEP_OPEN_ON_SUBMENU_OPENED); } /** * Measures the width of the given menu view. * * @param view The view to measure. * @return The width. */ protected static int measureIndividualMenuWidth(ListAdapter adapter, ViewGroup parent, Context context, int maxAllowedWidth) { // Menus don't tend to be long, so this is more sane than it looks. int maxWidth = 0; View itemView = null; int itemType = 0; final int widthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); final int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); final int count = adapter.getCount(); for (int i = 0; i < count; i++) { final int positionType = adapter.getItemViewType(i); if (positionType != itemType) { itemType = positionType; itemView = null; } if (parent == null) { parent = new FrameLayout(context); } itemView = adapter.getView(i, itemView, parent); itemView.measure(widthMeasureSpec, heightMeasureSpec); final int itemWidth = itemView.getMeasuredWidth(); if (itemWidth >= maxAllowedWidth) { return maxAllowedWidth; } else if (itemWidth > maxWidth) { maxWidth = itemWidth; } } return maxWidth; } /** * Converts the given ListAdapter originating from a menu, to a MenuAdapter, accounting for * the possibility of the parameter adapter actually wrapping the MenuAdapter. (That could * happen if a header view was added on the menu.) * * @param adapter * @return */ protected static MenuAdapter toMenuAdapter(ListAdapter adapter) { if (adapter instanceof HeaderViewListAdapter) { return (MenuAdapter) ((HeaderViewListAdapter) adapter).getWrappedAdapter(); } return (MenuAdapter) adapter; } /** * Returns whether icon spacing needs to be preserved for the given menu, based on whether any * of its items contains an icon. * * NOTE: This should only be used for non-overflow-only menus, because this method does not * take into account whether the menu items are being shown as part of the popup or or being * shown as actions in the action bar. * * @param menu * @return Whether to preserve icon spacing. */ protected static boolean shouldPreserveIconSpacing(MenuBuilder menu) { boolean preserveIconSpacing = false; final int count = menu.size(); for (int i = 0; i < count; i++) { MenuItem childItem = menu.getItem(i); if (childItem.isVisible() && childItem.getIcon() != null) { preserveIconSpacing = true; break; } } return preserveIconSpacing; } protected boolean closeMenuOnSubMenuOpened() { return true; } }