Java tutorial
/* * 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 android.annotation.UnsupportedAppUsage; import android.os.Build; import java.io.PrintWriter; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.Locale; /** * <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(Locale.ROOT) + 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 */ @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) 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))); } } /** @hide */ public static void printSizeValue(PrintWriter pw, long number) { float result = number; String suffix = ""; if (result > 900) { suffix = "KB"; result = result / 1024; } if (result > 900) { suffix = "MB"; result = result / 1024; } if (result > 900) { suffix = "GB"; result = result / 1024; } if (result > 900) { suffix = "TB"; result = result / 1024; } if (result > 900) { suffix = "PB"; result = result / 1024; } String value; if (result < 1) { value = String.format("%.2f", result); } else if (result < 10) { value = String.format("%.1f", result); } else if (result < 100) { value = String.format("%.0f", result); } else { value = String.format("%.0f", result); } pw.print(value); pw.print(suffix); } /** @hide */ public static String sizeValueToString(long number, StringBuilder outBuilder) { if (outBuilder == null) { outBuilder = new StringBuilder(32); } float result = number; String suffix = ""; if (result > 900) { suffix = "KB"; result = result / 1024; } if (result > 900) { suffix = "MB"; result = result / 1024; } if (result > 900) { suffix = "GB"; result = result / 1024; } if (result > 900) { suffix = "TB"; result = result / 1024; } if (result > 900) { suffix = "PB"; result = result / 1024; } String value; if (result < 1) { value = String.format("%.2f", result); } else if (result < 10) { value = String.format("%.1f", result); } else if (result < 100) { value = String.format("%.0f", result); } else { value = String.format("%.0f", result); } outBuilder.append(value); outBuilder.append(suffix); return outBuilder.toString(); } /** * Use prefixed constants (static final values) on given class to turn value * into human-readable string. * * @hide */ public static String valueToString(Class<?> clazz, String prefix, int value) { for (Field field : clazz.getDeclaredFields()) { final int modifiers = field.getModifiers(); if (Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers) && field.getType().equals(int.class) && field.getName().startsWith(prefix)) { try { if (value == field.getInt(null)) { return constNameWithoutPrefix(prefix, field); } } catch (IllegalAccessException ignored) { } } } return Integer.toString(value); } /** * Use prefixed constants (static final values) on given class to turn flags * into human-readable string. * * @hide */ public static String flagsToString(Class<?> clazz, String prefix, int flags) { final StringBuilder res = new StringBuilder(); boolean flagsWasZero = flags == 0; for (Field field : clazz.getDeclaredFields()) { final int modifiers = field.getModifiers(); if (Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers) && field.getType().equals(int.class) && field.getName().startsWith(prefix)) { try { final int value = field.getInt(null); if (value == 0 && flagsWasZero) { return constNameWithoutPrefix(prefix, field); } if ((flags & value) != 0) { flags &= ~value; res.append(constNameWithoutPrefix(prefix, field)).append('|'); } } catch (IllegalAccessException ignored) { } } } if (flags != 0 || res.length() == 0) { res.append(Integer.toHexString(flags)); } else { res.deleteCharAt(res.length() - 1); } return res.toString(); } private static String constNameWithoutPrefix(String prefix, Field field) { return field.getName().substring(prefix.length()); } }