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Android example source code file (MenuInflater.java)

This example Android source code file (MenuInflater.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, attributeset, content, error, inflateexception, ioexception, menu, menuinflater, menustate, no_id, runtimeexception, string, submenu, typedarray, util, utilities, utils, view, xml_group, xmlpullparserexception

The MenuInflater.java Android example source code

/*
 * Copyright (C) 2006 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.view;

import com.android.internal.view.menu.MenuItemImpl;

import java.io.IOException;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.content.res.XmlResourceParser;
import android.util.AttributeSet;
import android.util.Xml;

/**
 * This class is used to instantiate menu XML files into Menu objects.
 * <p>
 * For performance reasons, menu inflation relies heavily on pre-processing of
 * XML files that is done at build time. Therefore, it is not currently possible
 * to use MenuInflater with an XmlPullParser over a plain XML file at runtime;
 * it only works with an XmlPullParser returned from a compiled resource (R.
 * <em>something file.)
 */
public class MenuInflater {
    /** Menu tag name in XML. */
    private static final String XML_MENU = "menu";
    
    /** Group tag name in XML. */
    private static final String XML_GROUP = "group";
    
    /** Item tag name in XML. */
    private static final String XML_ITEM = "item";

    private static final int NO_ID = 0;
    
    private Context mContext;
    
    /**
     * Constructs a menu inflater.
     * 
     * @see Activity#getMenuInflater()
     */
    public MenuInflater(Context context) {
        mContext = context;
    }

    /**
     * Inflate a menu hierarchy from the specified XML resource. Throws
     * {@link InflateException} if there is an error.
     * 
     * @param menuRes Resource ID for an XML layout resource to load (e.g.,
     *            <code>R.menu.main_activity)
     * @param menu The Menu to inflate into. The items and submenus will be
     *            added to this Menu.
     */
    public void inflate(int menuRes, Menu menu) {
        XmlResourceParser parser = null;
        try {
            parser = mContext.getResources().getLayout(menuRes);
            AttributeSet attrs = Xml.asAttributeSet(parser);
            
            parseMenu(parser, attrs, menu);
        } catch (XmlPullParserException e) {
            throw new InflateException("Error inflating menu XML", e);
        } catch (IOException e) {
            throw new InflateException("Error inflating menu XML", e);
        } finally {
            if (parser != null) parser.close();
        }
    }

    /**
     * Called internally to fill the given menu. If a sub menu is seen, it will
     * call this recursively.
     */
    private void parseMenu(XmlPullParser parser, AttributeSet attrs, Menu menu)
            throws XmlPullParserException, IOException {
        MenuState menuState = new MenuState(menu);

        int eventType = parser.getEventType();
        String tagName;
        boolean lookingForEndOfUnknownTag = false;
        String unknownTagName = null;

        // This loop will skip to the menu start tag
        do {
            if (eventType == XmlPullParser.START_TAG) {
                tagName = parser.getName();
                if (tagName.equals(XML_MENU)) {
                    // Go to next tag
                    eventType = parser.next();
                    break;
                }
                
                throw new RuntimeException("Expecting menu, got " + tagName);
            }
            eventType = parser.next();
        } while (eventType != XmlPullParser.END_DOCUMENT);
        
        boolean reachedEndOfMenu = false;
        while (!reachedEndOfMenu) {
            switch (eventType) {
                case XmlPullParser.START_TAG:
                    if (lookingForEndOfUnknownTag) {
                        break;
                    }
                    
                    tagName = parser.getName();
                    if (tagName.equals(XML_GROUP)) {
                        menuState.readGroup(attrs);
                    } else if (tagName.equals(XML_ITEM)) {
                        menuState.readItem(attrs);
                    } else if (tagName.equals(XML_MENU)) {
                        // A menu start tag denotes a submenu for an item
                        SubMenu subMenu = menuState.addSubMenuItem();

                        // Parse the submenu into returned SubMenu
                        parseMenu(parser, attrs, subMenu);
                    } else {
                        lookingForEndOfUnknownTag = true;
                        unknownTagName = tagName;
                    }
                    break;
                    
                case XmlPullParser.END_TAG:
                    tagName = parser.getName();
                    if (lookingForEndOfUnknownTag && tagName.equals(unknownTagName)) {
                        lookingForEndOfUnknownTag = false;
                        unknownTagName = null;
                    } else if (tagName.equals(XML_GROUP)) {
                        menuState.resetGroup();
                    } else if (tagName.equals(XML_ITEM)) {
                        // Add the item if it hasn't been added (if the item was
                        // a submenu, it would have been added already)
                        if (!menuState.hasAddedItem()) {
                            menuState.addItem();
                        }
                    } else if (tagName.equals(XML_MENU)) {
                        reachedEndOfMenu = true;
                    }
                    break;
                    
                case XmlPullParser.END_DOCUMENT:
                    throw new RuntimeException("Unexpected end of document");
            }
            
            eventType = parser.next();
        }
    }
    
    /**
     * State for the current menu.
     * <p>
     * Groups can not be nested unless there is another menu (which will have
     * its state class).
     */
    private class MenuState {
        private Menu menu;

        /*
         * Group state is set on items as they are added, allowing an item to
         * override its group state. (As opposed to set on items at the group end tag.)
         */
        private int groupId;
        private int groupCategory;
        private int groupOrder;
        private int groupCheckable;
        private boolean groupVisible;
        private boolean groupEnabled;

        private boolean itemAdded;
        private int itemId;
        private int itemCategoryOrder;
        private String itemTitle;
        private String itemTitleCondensed;
        private int itemIconResId;
        private char itemAlphabeticShortcut;
        private char itemNumericShortcut;
        /**
         * Sync to attrs.xml enum:
         * - 0: none
         * - 1: all
         * - 2: exclusive
         */
        private int itemCheckable;
        private boolean itemChecked;
        private boolean itemVisible;
        private boolean itemEnabled;
        
        private static final int defaultGroupId = NO_ID;
        private static final int defaultItemId = NO_ID;
        private static final int defaultItemCategory = 0;
        private static final int defaultItemOrder = 0;
        private static final int defaultItemCheckable = 0;
        private static final boolean defaultItemChecked = false;
        private static final boolean defaultItemVisible = true;
        private static final boolean defaultItemEnabled = true;
        
        public MenuState(final Menu menu) {
            this.menu = menu;
            
            resetGroup();
        }
        
        public void resetGroup() {
            groupId = defaultGroupId;
            groupCategory = defaultItemCategory;
            groupOrder = defaultItemOrder;
            groupCheckable = defaultItemCheckable;
            groupVisible = defaultItemVisible;
            groupEnabled = defaultItemEnabled;
        }

        /**
         * Called when the parser is pointing to a group tag.
         */
        public void readGroup(AttributeSet attrs) {
            TypedArray a = mContext.obtainStyledAttributes(attrs,
                    com.android.internal.R.styleable.MenuGroup);
            
            groupId = a.getResourceId(com.android.internal.R.styleable.MenuGroup_id, defaultGroupId);
            groupCategory = a.getInt(com.android.internal.R.styleable.MenuGroup_menuCategory, defaultItemCategory);
            groupOrder = a.getInt(com.android.internal.R.styleable.MenuGroup_orderInCategory, defaultItemOrder);
            groupCheckable = a.getInt(com.android.internal.R.styleable.MenuGroup_checkableBehavior, defaultItemCheckable);
            groupVisible = a.getBoolean(com.android.internal.R.styleable.MenuGroup_visible, defaultItemVisible);
            groupEnabled = a.getBoolean(com.android.internal.R.styleable.MenuGroup_enabled, defaultItemEnabled);

            a.recycle();
        }
        
        /**
         * Called when the parser is pointing to an item tag.
         */
        public void readItem(AttributeSet attrs) {
            TypedArray a = mContext.obtainStyledAttributes(attrs,
                    com.android.internal.R.styleable.MenuItem);

            // Inherit attributes from the group as default value
            itemId = a.getResourceId(com.android.internal.R.styleable.MenuItem_id, defaultItemId);
            final int category = a.getInt(com.android.internal.R.styleable.MenuItem_menuCategory, groupCategory);
            final int order = a.getInt(com.android.internal.R.styleable.MenuItem_orderInCategory, groupOrder);
            itemCategoryOrder = (category & Menu.CATEGORY_MASK) | (order & Menu.USER_MASK);
            itemTitle = a.getString(com.android.internal.R.styleable.MenuItem_title);
            itemTitleCondensed = a.getString(com.android.internal.R.styleable.MenuItem_titleCondensed);
            itemIconResId = a.getResourceId(com.android.internal.R.styleable.MenuItem_icon, 0);
            itemAlphabeticShortcut =
                    getShortcut(a.getString(com.android.internal.R.styleable.MenuItem_alphabeticShortcut));
            itemNumericShortcut =
                    getShortcut(a.getString(com.android.internal.R.styleable.MenuItem_numericShortcut));
            if (a.hasValue(com.android.internal.R.styleable.MenuItem_checkable)) {
                // Item has attribute checkable, use it
                itemCheckable = a.getBoolean(com.android.internal.R.styleable.MenuItem_checkable, false) ? 1 : 0;
            } else {
                // Item does not have attribute, use the group's (group can have one more state
                // for checkable that represents the exclusive checkable)
                itemCheckable = groupCheckable;
            }
            itemChecked = a.getBoolean(com.android.internal.R.styleable.MenuItem_checked, defaultItemChecked);
            itemVisible = a.getBoolean(com.android.internal.R.styleable.MenuItem_visible, groupVisible);
            itemEnabled = a.getBoolean(com.android.internal.R.styleable.MenuItem_enabled, groupEnabled);
            
            a.recycle();
            
            itemAdded = false;
        }

        private char getShortcut(String shortcutString) {
            if (shortcutString == null) {
                return 0;
            } else {
                return shortcutString.charAt(0);
            }
        }
        
        private void setItem(MenuItem item) {
            item.setChecked(itemChecked)
                .setVisible(itemVisible)
                .setEnabled(itemEnabled)
                .setCheckable(itemCheckable >= 1)
                .setTitleCondensed(itemTitleCondensed)
                .setIcon(itemIconResId)
                .setAlphabeticShortcut(itemAlphabeticShortcut)
                .setNumericShortcut(itemNumericShortcut);

            if (itemCheckable >= 2) {
                ((MenuItemImpl) item).setExclusiveCheckable(true);
            }
        }
        
        public void addItem() {
            itemAdded = true;
            setItem(menu.add(groupId, itemId, itemCategoryOrder, itemTitle));
        }
        
        public SubMenu addSubMenuItem() {
            itemAdded = true;
            SubMenu subMenu = menu.addSubMenu(groupId, itemId, itemCategoryOrder, itemTitle);
            setItem(subMenu.getItem());
            return subMenu;
        }
        
        public boolean hasAddedItem() {
            return itemAdded;
        }
    }
    
}

Other Android examples (source code examples)

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