Android example source code file (WebIconDatabase.java)

This example Android source code file (WebIconDatabase.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, bitmap, bulk_request_icon, content, drawing, eventhandler, handler, hashmap, icon_result, iconlistener, iconresult, object, open, os, provider, release_icon, string, util, vector, webicondatabase

The WebIconDatabase.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.webkit;

import android.content.ContentResolver;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.os.Handler;
import android.os.Message;
import android.provider.Browser;
import android.util.Log;

import java.util.HashMap;
import java.util.Vector;

/**
 * Functions for manipulating the icon database used by WebView.
 * These functions require that a WebView be constructed before being invoked
 * and WebView.getIconDatabase() will return a WebIconDatabase object. This
 * WebIconDatabase object is a single instance and all methods operate on that
 * single object.
 */
public final class WebIconDatabase {
    private static final String LOGTAG = "WebIconDatabase";
    // Global instance of a WebIconDatabase
    private static WebIconDatabase sIconDatabase;
    // EventHandler for handling messages before and after the WebCore thread is
    // ready.
    private final EventHandler mEventHandler = new EventHandler();

    // Class to handle messages before WebCore is ready
    private static class EventHandler extends Handler {
        // Message ids
        static final int OPEN         = 0;
        static final int CLOSE        = 1;
        static final int REMOVE_ALL   = 2;
        static final int REQUEST_ICON = 3;
        static final int RETAIN_ICON  = 4;
        static final int RELEASE_ICON = 5;
        static final int BULK_REQUEST_ICON = 6;
        // Message for dispatching icon request results
        private static final int ICON_RESULT = 10;
        // Actual handler that runs in WebCore thread
        private Handler mHandler;
        // Vector of messages before the WebCore thread is ready
        private Vector<Message> mMessages = new Vector();
        // Class to handle a result dispatch
        private class IconResult {
            private final String mUrl;
            private final Bitmap mIcon;
            private final IconListener mListener;
            IconResult(String url, Bitmap icon, IconListener l) {
                mUrl = url;
                mIcon = icon;
                mListener = l;
            }
            void dispatch() {
                mListener.onReceivedIcon(mUrl, mIcon);
            }
        }

        @Override
        public void handleMessage(Message msg) {
            // Note: This is the message handler for the UI thread.
            switch (msg.what) {
                case ICON_RESULT:
                    ((IconResult) msg.obj).dispatch();
                    break;
            }
        }

        // Called by WebCore thread to create the actual handler
        private synchronized void createHandler() {
            if (mHandler == null) {
                mHandler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        // Note: This is the message handler for the WebCore
                        // thread.
                        switch (msg.what) {
                            case OPEN:
                                nativeOpen((String) msg.obj);
                                break;

                            case CLOSE:
                                nativeClose();
                                break;

                            case REMOVE_ALL:
                                nativeRemoveAllIcons();
                                break;

                            case REQUEST_ICON:
                                IconListener l = (IconListener) msg.obj;
                                String url = msg.getData().getString("url");
                                requestIconAndSendResult(url, l);
                                break;

                            case BULK_REQUEST_ICON:
                                bulkRequestIcons(msg);
                                break;

                            case RETAIN_ICON:
                                nativeRetainIconForPageUrl((String) msg.obj);
                                break;

                            case RELEASE_ICON:
                                nativeReleaseIconForPageUrl((String) msg.obj);
                                break;
                        }
                    }
                };
                // Transfer all pending messages
                for (int size = mMessages.size(); size > 0; size--) {
                    mHandler.sendMessage(mMessages.remove(0));
                }
                mMessages = null;
            }
        }

        private synchronized boolean hasHandler() {
            return mHandler != null;
        }

        private synchronized void postMessage(Message msg) {
            if (mMessages != null) {
                mMessages.add(msg);
            } else {
                mHandler.sendMessage(msg);
            }
        }

        private void bulkRequestIcons(Message msg) {
            HashMap map = (HashMap) msg.obj;
            IconListener listener = (IconListener) map.get("listener");
            ContentResolver cr = (ContentResolver) map.get("contentResolver");
            String where = (String) map.get("where");

            Cursor c = null;
            try {
                c = cr.query(
                        Browser.BOOKMARKS_URI,
                        new String[] { Browser.BookmarkColumns.URL },
                        where, null, null);
                if (c.moveToFirst()) {
                    do {
                        String url = c.getString(0);
                        requestIconAndSendResult(url, listener);
                    } while (c.moveToNext());
                }
            } catch (IllegalStateException e) {
                Log.e(LOGTAG, "BulkRequestIcons", e);
            } finally {
                if (c != null) c.close();
            }
        }

        private void requestIconAndSendResult(String url, IconListener listener) {
            Bitmap icon = nativeIconForPageUrl(url);
            if (icon != null) {
                sendMessage(obtainMessage(ICON_RESULT,
                            new IconResult(url, icon, listener)));
            }
        }
    }

    /**
     * Interface for receiving icons from the database.
     */
    public interface IconListener {
        /**
         * Called when the icon has been retrieved from the database and the
         * result is non-null.
         * @param url The url passed in the request.
         * @param icon The favicon for the given url.
         */
        public void onReceivedIcon(String url, Bitmap icon);
    }

    /**
     * Open a the icon database and store the icons in the given path.
     * @param path The directory path where the icon database will be stored.
     * @return True if the database was successfully opened or created in
     *         the given path.
     */
    public void open(String path) {
        if (path != null) {
            mEventHandler.postMessage(
                    Message.obtain(null, EventHandler.OPEN, path));
        }
    }

    /**
     * Close the shared instance of the icon database.
     */
    public void close() {
        mEventHandler.postMessage(
                Message.obtain(null, EventHandler.CLOSE));
    }

    /**
     * Removes all the icons in the database.
     */
    public void removeAllIcons() {
        mEventHandler.postMessage(
                Message.obtain(null, EventHandler.REMOVE_ALL));
    }

    /**
     * Request the Bitmap representing the icon for the given page
     * url. If the icon exists, the listener will be called with the result.
     * @param url The page's url.
     * @param listener An implementation on IconListener to receive the result.
     */
    public void requestIconForPageUrl(String url, IconListener listener) {
        if (listener == null || url == null) {
            return;
        }
        Message msg = Message.obtain(null, EventHandler.REQUEST_ICON, listener);
        msg.getData().putString("url", url);
        mEventHandler.postMessage(msg);
    }

    /** {@hide}
     */
    public void bulkRequestIconForPageUrl(ContentResolver cr, String where,
            IconListener listener) {
        if (listener == null) {
            return;
        }

        // Special case situation: we don't want to add this message to the
        // queue if there is no handler because we may never have a real
        // handler to service the messages and the cursor will never get
        // closed.
        if (mEventHandler.hasHandler()) {
            // Don't use Bundle as it is parcelable.
            HashMap<String, Object> map = new HashMap();
            map.put("contentResolver", cr);
            map.put("where", where);
            map.put("listener", listener);
            Message msg =
                    Message.obtain(null, EventHandler.BULK_REQUEST_ICON, map);
            mEventHandler.postMessage(msg);
        }
    }

    /**
     * Retain the icon for the given page url.
     * @param url The page's url.
     */
    public void retainIconForPageUrl(String url) {
        if (url != null) {
            mEventHandler.postMessage(
                    Message.obtain(null, EventHandler.RETAIN_ICON, url));
        }
    }

    /**
     * Release the icon for the given page url.
     * @param url The page's url.
     */
    public void releaseIconForPageUrl(String url) {
        if (url != null) {
            mEventHandler.postMessage(
                    Message.obtain(null, EventHandler.RELEASE_ICON, url));
        }
    }

    /**
     * Get the global instance of WebIconDatabase.
     * @return A single instance of WebIconDatabase. It will be the same
     *         instance for the current process each time this method is
     *         called.
     */
    public static WebIconDatabase getInstance() {
        // XXX: Must be created in the UI thread.
        if (sIconDatabase == null) {
            sIconDatabase = new WebIconDatabase();
        }
        return sIconDatabase;
    }

    /**
     * Create the internal handler and transfer all pending messages.
     * XXX: Called by WebCore thread only!
     */
    /*package*/ void createHandler() {
        mEventHandler.createHandler();
    }

    /**
     * Private constructor to avoid anyone else creating an instance.
     */
    private WebIconDatabase() {}

    // Native functions
    private static native void nativeOpen(String path);
    private static native void nativeClose();
    private static native void nativeRemoveAllIcons();
    private static native Bitmap nativeIconForPageUrl(String url);
    private static native void nativeRetainIconForPageUrl(String url);
    private static native void nativeReleaseIconForPageUrl(String url);
}