Preloader.java revision f27b710afe310d5df6ae3fac9c88b23ac78cbfe6 
1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16package com.android.browser;
17
18import android.content.Context;
19import android.os.Handler;
20import android.os.Looper;
21import android.util.Log;
22import android.webkit.WebView;
23
24import java.util.Map;
25
26/**
27 * Singleton class for handling preload requests.
28 */
29public class Preloader {
30
31    private final static String LOGTAG = "browser.preloader";
32    private final static boolean LOGD_ENABLED = com.android.browser.Browser.LOGD_ENABLED;
33
34    private static final int PRERENDER_TIMEOUT_MILLIS = 30 * 1000; // 30s
35
36    private static Preloader sInstance;
37
38    private final Context mContext;
39    private final Handler mHandler;
40    private final BrowserWebViewFactory mFactory;
41    private volatile PreloaderSession mSession;
42
43    public static void initialize(Context context) {
44        sInstance = new Preloader(context);
45    }
46
47    public static Preloader getInstance() {
48        return sInstance;
49    }
50
51    private Preloader(Context context) {
52        mContext = context;
53        mHandler = new Handler(Looper.getMainLooper());
54        mSession = null;
55        mFactory = new BrowserWebViewFactory(context);
56
57    }
58
59    private PreloaderSession getSession(String id) {
60        if (mSession == null) {
61            if (LOGD_ENABLED) Log.d(LOGTAG, "Create new preload session " + id);
62            mSession = new PreloaderSession(id);
63            WebViewTimersControl.getInstance().onPrerenderStart(
64                    mSession.getWebView());
65            return mSession;
66        } else if (mSession.mId.equals(id)) {
67            if (LOGD_ENABLED) Log.d(LOGTAG, "Returning existing preload session " + id);
68            return mSession;
69        }
70
71        if (LOGD_ENABLED) Log.d(LOGTAG, "Existing session in progress : " + mSession.mId +
72                " returning null.");
73        return null;
74    }
75
76    private PreloaderSession takeSession(String id) {
77        PreloaderSession s = null;
78        if (mSession != null && mSession.mId.equals(id)) {
79            s = mSession;
80            mSession = null;
81        }
82
83        if (s != null) {
84            s.cancelTimeout();
85        }
86
87        WebViewTimersControl.getInstance().onPrerenderDone(s == null ? null : s.getWebView());
88        return s;
89    }
90
91    public void handlePreloadRequest(String id, String url, Map<String, String> headers,
92            String searchBoxQuery) {
93        PreloaderSession s = getSession(id);
94        if (s == null) {
95            if (LOGD_ENABLED) Log.d(LOGTAG, "Discarding preload request, existing"
96                    + " session in progress");
97            return;
98        }
99
100        s.touch(); // reset timer
101        PreloadedTabControl tab = s.getTabControl();
102        if (searchBoxQuery != null) {
103            tab.loadUrlIfChanged(url, headers);
104            tab.setQuery(searchBoxQuery);
105        } else {
106            tab.loadUrl(url, headers);
107        }
108    }
109
110    public void discardPreload(String id) {
111        PreloaderSession s = takeSession(id);
112        if (s != null) {
113            if (LOGD_ENABLED) Log.d(LOGTAG, "Discard preload session " + id);
114            PreloadedTabControl t = s.getTabControl();
115            t.destroy();
116        } else {
117            if (LOGD_ENABLED) Log.d(LOGTAG, "Ignored discard request " + id);
118        }
119    }
120
121    /**
122     * Return a preloaded tab, and remove it from the preloader. This is used when the
123     * view is about to be displayed.
124     */
125    public PreloadedTabControl getPreloadedTab(String id) {
126        PreloaderSession s = takeSession(id);
127        if (LOGD_ENABLED) Log.d(LOGTAG, "Showing preload session " + id + "=" + s);
128        return s == null ? null : s.getTabControl();
129    }
130
131    private class PreloaderSession {
132        private final String mId;
133        private final PreloadedTabControl mTabControl;
134
135        private final Runnable mTimeoutTask = new Runnable(){
136            @Override
137            public void run() {
138                if (LOGD_ENABLED) Log.d(LOGTAG, "Preload session timeout " + mId);
139                discardPreload(mId);
140            }};
141
142        public PreloaderSession(String id) {
143            mId = id;
144            mTabControl = new PreloadedTabControl(
145                    new Tab(new PreloadController(mContext), mFactory.createWebView(false)));
146            touch();
147        }
148
149        public void cancelTimeout() {
150            mHandler.removeCallbacks(mTimeoutTask);
151        }
152
153        public void touch() {
154            cancelTimeout();
155            mHandler.postDelayed(mTimeoutTask, PRERENDER_TIMEOUT_MILLIS);
156        }
157
158        public PreloadedTabControl getTabControl() {
159            return mTabControl;
160        }
161
162        public WebView getWebView() {
163            Tab t = mTabControl.getTab();
164            return t == null? null : t.getWebView();
165        }
166
167    }
168
169}
170