1 /* 2 * Copyright (C) 2006 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 */ 16 17 package android.webkit; 18 19 import java.io.Serializable; 20 import java.util.ArrayList; 21 22 /** 23 * This class contains the back/forward list for a WebView. 24 * WebView.copyBackForwardList() will return a copy of this class used to 25 * inspect the entries in the list. 26 */ 27 public class WebBackForwardList implements Cloneable, Serializable { 28 // Current position in the list. 29 private int mCurrentIndex; 30 // ArrayList of WebHistoryItems for maintaining our copy. 31 private ArrayList<WebHistoryItem> mArray; 32 // Flag to indicate that the list is invalid 33 private boolean mClearPending; 34 35 /** 36 * Construct a back/forward list used by clients of WebView. 37 */ WebBackForwardList()38 /*package*/ WebBackForwardList() { 39 mCurrentIndex = -1; 40 mArray = new ArrayList<WebHistoryItem>(); 41 } 42 43 /** 44 * Return the current history item. This method returns null if the list is 45 * empty. 46 * @return The current history item. 47 */ getCurrentItem()48 public synchronized WebHistoryItem getCurrentItem() { 49 return getItemAtIndex(mCurrentIndex); 50 } 51 52 /** 53 * Get the index of the current history item. This index can be used to 54 * directly index into the array list. 55 * @return The current index from 0...n or -1 if the list is empty. 56 */ getCurrentIndex()57 public synchronized int getCurrentIndex() { 58 return mCurrentIndex; 59 } 60 61 /** 62 * Get the history item at the given index. The index range is from 0...n 63 * where 0 is the first item and n is the last item. 64 * @param index The index to retrieve. 65 */ getItemAtIndex(int index)66 public synchronized WebHistoryItem getItemAtIndex(int index) { 67 if (index < 0 || index >= getSize()) { 68 return null; 69 } 70 return mArray.get(index); 71 } 72 73 /** 74 * Get the total size of the back/forward list. 75 * @return The size of the list. 76 */ getSize()77 public synchronized int getSize() { 78 return mArray.size(); 79 } 80 81 /** 82 * Mark the back/forward list as having a pending clear. This is used on the 83 * UI side to mark the list as being invalid during the clearHistory method. 84 */ setClearPending()85 /*package*/ synchronized void setClearPending() { 86 mClearPending = true; 87 } 88 89 /** 90 * Return the status of the clear flag. This is used on the UI side to 91 * determine if the list is valid for checking things like canGoBack. 92 */ getClearPending()93 /*package*/ synchronized boolean getClearPending() { 94 return mClearPending; 95 } 96 97 /** 98 * Add a new history item to the list. This will remove all items after the 99 * current item and append the new item to the end of the list. Called from 100 * the WebCore thread only. Synchronized because the UI thread may be 101 * reading the array or the current index. 102 * @param item A new history item. 103 */ addHistoryItem(WebHistoryItem item)104 /*package*/ synchronized void addHistoryItem(WebHistoryItem item) { 105 // Update the current position because we are going to add the new item 106 // in that slot. 107 ++mCurrentIndex; 108 // If the current position is not at the end, remove all history items 109 // after the current item. 110 final int size = mArray.size(); 111 final int newPos = mCurrentIndex; 112 if (newPos != size) { 113 for (int i = size - 1; i >= newPos; i--) { 114 final WebHistoryItem h = mArray.remove(i); 115 } 116 } 117 // Add the item to the list. 118 mArray.add(item); 119 } 120 121 /** 122 * Clear the back/forward list. Called from the WebCore thread. 123 */ close(int nativeFrame)124 /*package*/ synchronized void close(int nativeFrame) { 125 // Clear the array first because nativeClose will call addHistoryItem 126 // with the current item. 127 mArray.clear(); 128 mCurrentIndex = -1; 129 nativeClose(nativeFrame); 130 // Reset the clear flag 131 mClearPending = false; 132 } 133 134 /* Remove the item at the given index. Called by JNI only. */ removeHistoryItem(int index)135 private synchronized void removeHistoryItem(int index) { 136 // XXX: This is a special case. Since the callback is only triggered 137 // when removing the first item, we can assert that the index is 0. 138 // This lets us change the current index without having to query the 139 // native BackForwardList. 140 if (DebugFlags.WEB_BACK_FORWARD_LIST && (index != 0)) { 141 throw new AssertionError(); 142 } 143 final WebHistoryItem h = mArray.remove(index); 144 // XXX: If we ever add another callback for removing history items at 145 // any index, this will no longer be valid. 146 mCurrentIndex--; 147 } 148 149 /** 150 * Clone the entire object to be used in the UI thread by clients of 151 * WebView. This creates a copy that should never be modified by any of the 152 * webkit package classes. 153 */ clone()154 protected synchronized WebBackForwardList clone() { 155 WebBackForwardList l = new WebBackForwardList(); 156 if (mClearPending) { 157 // If a clear is pending, return a copy with only the current item. 158 l.addHistoryItem(getCurrentItem()); 159 return l; 160 } 161 l.mCurrentIndex = mCurrentIndex; 162 int size = getSize(); 163 l.mArray = new ArrayList<WebHistoryItem>(size); 164 for (int i = 0; i < size; i++) { 165 // Add a copy of each WebHistoryItem 166 l.mArray.add(mArray.get(i).clone()); 167 } 168 return l; 169 } 170 171 /** 172 * Set the new history index. 173 * @param newIndex The new history index. 174 */ setCurrentIndex(int newIndex)175 /*package*/ synchronized void setCurrentIndex(int newIndex) { 176 mCurrentIndex = newIndex; 177 } 178 179 /** 180 * Restore the history index. 181 */ restoreIndex(int nativeFrame, int index)182 /*package*/ static native synchronized void restoreIndex(int nativeFrame, 183 int index); 184 185 /* Close the native list. */ nativeClose(int nativeFrame)186 private static native void nativeClose(int nativeFrame); 187 } 188