David Tseng | 663744c | 2011-06-06 13:24:22 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2010 Google Inc. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 5 | * use this file except in compliance with the License. You may obtain a copy of |
| 6 | * 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, WITHOUT |
| 12 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 13 | * License for the specific language governing permissions and limitations under |
| 14 | * the License. |
| 15 | */ |
| 16 | package com.android.accessibility; |
| 17 | |
| 18 | import org.xml.sax.Attributes; |
| 19 | import org.xml.sax.Locator; |
| 20 | import org.xml.sax.helpers.DefaultHandler; |
| 21 | |
| 22 | import java.io.File; |
| 23 | import java.net.MalformedURLException; |
| 24 | import java.net.URL; |
| 25 | import java.net.URLClassLoader; |
| 26 | import java.util.ArrayList; |
| 27 | import java.util.HashSet; |
| 28 | import java.util.List; |
| 29 | import java.util.Set; |
| 30 | import java.util.logging.Logger; |
| 31 | |
| 32 | /** |
| 33 | * An object that handles Android xml layout files in conjunction with an |
| 34 | * XMLParser for the purpose of testing for accessibility based on the following |
| 35 | * rule: |
| 36 | * <p> |
| 37 | * If the Element tag is ImageView (or a subclass of ImageView), then the tag |
| 38 | * must contain a contentDescription attribute. |
| 39 | * <p> |
| 40 | * This class also has logic to ascertain the subclasses of ImageView and thus |
| 41 | * requires the path to an Android sdk jar. The subclasses are saved for |
| 42 | * application of the above rule when a new XML document tag needs processing. |
| 43 | * |
| 44 | * @author dtseng@google.com (David Tseng) |
| 45 | */ |
| 46 | public class AccessibilityValidationContentHandler extends DefaultHandler { |
| 47 | /** Used to obtain line information within the XML file. */ |
| 48 | private Locator mLocator; |
| 49 | /** The location of the file we are handling. */ |
| 50 | private final String mPath; |
| 51 | /** The total number of errors within the current file. */ |
| 52 | private int mValidationErrors = 0; |
| 53 | |
| 54 | /** |
| 55 | * Element tags we have seen before and determined not to be |
| 56 | * subclasses of ImageView. |
| 57 | */ |
| 58 | private final Set<String> mExclusionList = new HashSet<String>(); |
| 59 | |
| 60 | /** The path to the Android sdk jar file. */ |
| 61 | private final File mAndroidSdkPath; |
| 62 | |
| 63 | /** |
| 64 | * The ImageView class stored for easy comparison while handling content. It |
| 65 | * gets initialized in the {@link AccessibilityValidationHandler} |
| 66 | * constructor if not already done so. |
| 67 | */ |
| 68 | private static Class<?> sImageViewElement; |
| 69 | |
| 70 | /** |
| 71 | * A class loader properly initialized and reusable across files. It gets |
| 72 | * initialized in the {@link AccessibilityValidationHandler} constructor if |
| 73 | * not already done so. |
| 74 | */ |
| 75 | private static ClassLoader sValidationClassLoader; |
| 76 | |
| 77 | /** Attributes we test existence for (for example, contentDescription). */ |
| 78 | private static final HashSet<String> sExpectedAttributes = |
| 79 | new HashSet<String>(); |
| 80 | |
| 81 | /** The object that handles our logging. */ |
| 82 | private static final Logger sLogger = Logger.getLogger("android.accessibility"); |
| 83 | |
| 84 | /** |
| 85 | * Construct an AccessibilityValidationContentHandler object with the file |
| 86 | * on which validation occurs and a path to the Android sdk jar. Then, |
| 87 | * initialize the class members if not previously done so. |
| 88 | * |
| 89 | * @throws IllegalArgumentException |
| 90 | * when given an invalid Android sdk path or when unable to |
| 91 | * locate {@link ImageView} class. |
| 92 | */ |
| 93 | public AccessibilityValidationContentHandler(String fullyQualifiedPath, |
| 94 | File androidSdkPath) throws IllegalArgumentException { |
| 95 | mPath = fullyQualifiedPath; |
| 96 | mAndroidSdkPath = androidSdkPath; |
| 97 | |
| 98 | initializeAccessibilityValidationContentHandler(); |
| 99 | } |
| 100 | |
| 101 | /** |
| 102 | * Used to log line numbers of errors in {@link #startElement}. |
| 103 | */ |
| 104 | @Override |
| 105 | public void setDocumentLocator(Locator locator) { |
| 106 | mLocator = locator; |
| 107 | } |
| 108 | |
| 109 | /** |
| 110 | * For each subclass of ImageView, test for existence of the specified |
| 111 | * attributes. |
| 112 | */ |
| 113 | @Override |
| 114 | public void startElement(String uri, String localName, String qName, |
| 115 | Attributes atts) { |
| 116 | Class<?> potentialClass; |
| 117 | String classPath = "android.widget." + localName; |
| 118 | try { |
| 119 | potentialClass = sValidationClassLoader.loadClass(classPath); |
| 120 | } catch (ClassNotFoundException cnfException) { |
| 121 | return; // do nothing as the class doesn't exist. |
| 122 | } |
| 123 | |
| 124 | // if we already determined this class path isn't a subclass of |
| 125 | // ImageView, skip it. |
| 126 | // Otherwise, check to see if it is a subclass. |
| 127 | if (mExclusionList.contains(classPath)) { |
| 128 | return; |
| 129 | } else if (!sImageViewElement.isAssignableFrom(potentialClass)) { |
| 130 | mExclusionList.add(classPath); |
| 131 | return; |
| 132 | } |
| 133 | |
| 134 | boolean hasAttribute = false; |
| 135 | StringBuilder extendedOutput = new StringBuilder(); |
| 136 | for (int i = 0; i < atts.getLength(); i++) { |
| 137 | String currentAttribute = atts.getLocalName(i).toLowerCase(); |
| 138 | if (sExpectedAttributes.contains(currentAttribute)) { |
| 139 | hasAttribute = true; |
| 140 | break; |
| 141 | } else if (currentAttribute.equals("id")) { |
| 142 | extendedOutput.append("|id=" + currentAttribute); |
| 143 | } else if (currentAttribute.equals("src")) { |
| 144 | extendedOutput.append("|src=" + atts.getValue(i)); |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | if (!hasAttribute) { |
| 149 | if (getValidationErrors() == 0) { |
| 150 | sLogger.info(mPath); |
| 151 | } |
| 152 | sLogger.info(String.format("ln: %s. Error in %s%s tag.", |
| 153 | mLocator.getLineNumber(), localName, extendedOutput)); |
| 154 | mValidationErrors++; |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * Returns the total number of errors encountered in this file. |
| 160 | */ |
| 161 | public int getValidationErrors() { |
| 162 | return mValidationErrors; |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * Set the class loader and ImageView class objects that will be used during |
| 167 | * the startElement validation logic. The class loader encompasses the class |
| 168 | * paths provided. |
| 169 | * |
| 170 | * @throws ClassNotFoundException |
| 171 | * when the ImageView Class object could not be found within the |
| 172 | * provided class loader. |
| 173 | */ |
| 174 | public static void setClassLoaderAndBaseClass(URL[] urlSearchPaths) |
| 175 | throws ClassNotFoundException { |
| 176 | sValidationClassLoader = new URLClassLoader(urlSearchPaths); |
| 177 | sImageViewElement = |
| 178 | sValidationClassLoader.loadClass("android.widget.ImageView"); |
| 179 | } |
| 180 | |
| 181 | /** |
| 182 | * Adds an attribute that will be tested for existence in |
| 183 | * {@link #startElement}. The search will always be case-insensitive. |
| 184 | */ |
| 185 | private static void addExpectedAttribute(String attribute) { |
| 186 | sExpectedAttributes.add(attribute.toLowerCase()); |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * Initializes the class loader and {@link ImageView} Class objects. |
| 191 | * |
| 192 | * @throws IllegalArgumentException |
| 193 | * when either an invalid path is provided or ImageView cannot |
| 194 | * be found in the classpaths. |
| 195 | */ |
| 196 | private void initializeAccessibilityValidationContentHandler() |
| 197 | throws IllegalArgumentException { |
| 198 | if (sValidationClassLoader != null && sImageViewElement != null) { |
| 199 | return; // These objects are already initialized. |
| 200 | } |
| 201 | try { |
| 202 | setClassLoaderAndBaseClass(new URL[] { mAndroidSdkPath.toURL() }); |
| 203 | } catch (MalformedURLException mUException) { |
| 204 | throw new IllegalArgumentException("invalid android sdk path", |
| 205 | mUException); |
| 206 | } catch (ClassNotFoundException cnfException) { |
| 207 | throw new IllegalArgumentException( |
| 208 | "Unable to find ImageView class.", cnfException); |
| 209 | } |
| 210 | |
| 211 | // Add all of the expected attributes. |
| 212 | addExpectedAttribute("contentDescription"); |
| 213 | } |
| 214 | } |