core/java/android/util/DebugUtils.java

/*
 * Copyright (C) 2007 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.util;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

/**
 * <p>Various utilities for debugging and logging.</p>
 */
public class DebugUtils {
    /** @hide */ public DebugUtils() {}

    /**
     * <p>Filters objects against the <code>ANDROID_OBJECT_FILTER</code>
     * environment variable. This environment variable can filter objects
     * based on their class name and attribute values.</p>
     *
     * <p>Here is the syntax for <code>ANDROID_OBJECT_FILTER</code>:</p>
     *
     * <p><code>ClassName@attribute1=value1@attribute2=value2...</code></p>
     *
     * <p>Examples:</p>
     * <ul>
     * <li>Select TextView instances: <code>TextView</code></li>
     * <li>Select TextView instances of text "Loading" and bottom offset of 22:
     * <code>TextView@text=Loading.*@bottom=22</code></li>
     * </ul>
     *
     * <p>The class name and the values are regular expressions.</p>
     *
     * <p>This class is useful for debugging and logging purpose:</p>
     * <pre>
     * if (DEBUG) {
     *   if (DebugUtils.isObjectSelected(childView) && LOGV_ENABLED) {
     *     Log.v(TAG, "Object " + childView + " logged!");
     *   }
     * }
     * </pre>
     *
     * <p><strong>NOTE</strong>: This method is very expensive as it relies
     * heavily on regular expressions and reflection. Calls to this method
     * should always be stripped out of the release binaries and avoided
     * as much as possible in debug mode.</p>
     *
     * @param object any object to match against the ANDROID_OBJECT_FILTER
     *        environement variable
     * @return true if object is selected by the ANDROID_OBJECT_FILTER
     *         environment variable, false otherwise
     */
    public static boolean isObjectSelected(Object object) {
        boolean match = false;
        String s = System.getenv("ANDROID_OBJECT_FILTER");
        if (s != null && s.length() > 0) {
            String[] selectors = s.split("@");
            // first selector == class name
            if (object.getClass().getSimpleName().matches(selectors[0])) {
                // check potential attributes
                for (int i = 1; i < selectors.length; i++) {
                    String[] pair = selectors[i].split("=");
                    Class<?> klass = object.getClass();
                    try {
                        Method declaredMethod = null;
                        Class<?> parent = klass;
                        do {
                            declaredMethod = parent.getDeclaredMethod("get" +
                                    pair[0].substring(0, 1).toUpperCase() +
                                    pair[0].substring(1),
                                    (Class[]) null);
                        } while ((parent = klass.getSuperclass()) != null &&
                                declaredMethod == null);

                        if (declaredMethod != null) {
                            Object value = declaredMethod
                                    .invoke(object, (Object[])null);
                            match |= (value != null ?
                                    value.toString() : "null").matches(pair[1]);
                        }
                    } catch (NoSuchMethodException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    } catch (InvocationTargetException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return match;
    }

    /** @hide */
    public static void buildShortClassTag(Object cls, StringBuilder out) {
        if (cls == null) {
            out.append("null");
        } else {
            String simpleName = cls.getClass().getSimpleName();
            if (simpleName == null || simpleName.isEmpty()) {
                simpleName = cls.getClass().getName();
                int end = simpleName.lastIndexOf('.');
                if (end > 0) {
                    simpleName = simpleName.substring(end+1);
                }
            }
            out.append(simpleName);
            out.append('{');
            out.append(Integer.toHexString(System.identityHashCode(cls)));
        }
    }

}