DebugUtils.java revision a2ea747faaf5fcd437afbaaf4085cfc29e7c16b8 
1/*
2 * Copyright (C) 2007 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
17package android.util;
18
19import java.lang.reflect.Method;
20import java.lang.reflect.InvocationTargetException;
21
22/**
23 * <p>Various utilities for debugging and logging.</p>
24 */
25public class DebugUtils {
26    /**
27     * <p>Filters objects against the <code>ANDROID_OBJECT_FILTER</code>
28     * environment variable. This environment variable can filter objects
29     * based on their class name and attribute values.</p>
30     *
31     * <p>Here is the syntax for <code>ANDROID_OBJECT_FILTER</code>:</p>
32     *
33     * <p><code>ClassName@attribute1=value1@attribute2=value2...</code></p>
34     *
35     * <p>Examples:</p>
36     * <ul>
37     * <li>Select TextView instances: <code>TextView</code></li>
38     * <li>Select TextView instances of text "Loading" and bottom offset of 22:
39     * <code>TextView@text=Loading.*@bottom=22</code></li>
40     * </ul>
41     *
42     * <p>The class name and the values are regular expressions.</p>
43     *
44     * <p>This class is useful for debugging and logging purpose:</p>
45     * <pre>
46     * if (DEBUG) {
47     *   if (DebugUtils.isObjectSelected(childView) && LOGV_ENABLED) {
48     *     Log.v(TAG, "Object " + childView + " logged!");
49     *   }
50     * }
51     * </pre>
52     *
53     * <p><strong>NOTE</strong>: This method is very expensive as it relies
54     * heavily on regular expressions and reflection. Calls to this method
55     * should always be stripped out of the release binaries and avoided
56     * as much as possible in debug mode.</p>
57     *
58     * @param object any object to match against the ANDROID_OBJECT_FILTER
59     *        environement variable
60     * @return true if object is selected by the ANDROID_OBJECT_FILTER
61     *         environment variable, false otherwise
62     */
63    public static boolean isObjectSelected(Object object) {
64        boolean match = false;
65        String s = System.getenv("ANDROID_OBJECT_FILTER");
66        if (s != null && s.length() > 0) {
67            String[] selectors = s.split("@");
68            // first selector == class name
69            if (object.getClass().getSimpleName().matches(selectors[0])) {
70                // check potential attributes
71                for (int i = 1; i < selectors.length; i++) {
72                    String[] pair = selectors[i].split("=");
73                    Class<?> klass = object.getClass();
74                    try {
75                        Method declaredMethod = null;
76                        Class<?> parent = klass;
77                        do {
78                            declaredMethod = parent.getDeclaredMethod("get" +
79                                    pair[0].substring(0, 1).toUpperCase() +
80                                    pair[0].substring(1),
81                                    (Class[]) null);
82                        } while ((parent = klass.getSuperclass()) != null &&
83                                declaredMethod == null);
84
85                        if (declaredMethod != null) {
86                            Object value = declaredMethod
87                                    .invoke(object, (Object[])null);
88                            match |= (value != null ?
89                                    value.toString() : "null").matches(pair[1]);
90                        }
91                    } catch (NoSuchMethodException e) {
92                        e.printStackTrace();
93                    } catch (IllegalAccessException e) {
94                        e.printStackTrace();
95                    } catch (InvocationTargetException e) {
96                        e.printStackTrace();
97                    }
98                }
99            }
100        }
101        return match;
102    }
103
104    /** @hide */
105    public static void buildShortClassTag(Object cls, StringBuilder out) {
106        if (cls == null) {
107            out.append("null");
108        } else {
109            String simpleName = cls.getClass().getSimpleName();
110            if (simpleName == null || simpleName.isEmpty()) {
111                simpleName = cls.getClass().getName();
112                int end = simpleName.lastIndexOf('.');
113                if (end > 0) {
114                    simpleName = simpleName.substring(end+1);
115                }
116            }
117            out.append(simpleName);
118            out.append('{');
119            out.append(Integer.toHexString(System.identityHashCode(cls)));
120        }
121    }
122
123}
124