LOG类：
public final class
Log
extends Object
java.lang.Object
android.util.Log
Constants
int
ASSERT
Priority constant for the println method.
int
DEBUG
Priority constant for the println method; use Log.d. 输出DEBUG故障日志信息
int
ERROR
Priority constant for the println method; use Log.e. 输出ERROR错误日志信息
int
INFO
Priority constant for the println method; use Log.i. 输出INFO程序日志信息
int
VERBOSE
Priority constant for the println method; use Log.v. 输出VERBOSE冗余日志信息
intWARN Priority constant for the println method; use Log.w. 输出WARN警告日志信息
/** Copyright (C) 2006 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 com.android.internal.os.RuntimeInit;import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.UnknownHostException;/*** API for sending log output.** <p>Generally, use the Log.v() Log.d() Log.i() Log.w() and Log.e()* methods.** <p>The order in terms of verbosity, from least to most is* ERROR, WARN, INFO, DEBUG, VERBOSE. Verbose should never be compiled* into an application except during development. Debug logs are compiled* in but stripped at runtime. Error, warning and info logs are always kept.** <p><b>Tip:</b> A good convention is to declare a <code>TAG</code> constant* in your class:** <pre>private static final String TAG = "MyActivity";</pre>** and use that in subsequent calls to the log methods.* </p>** <p><b>Tip:</b> Don't forget that when you make a call like* <pre>Log.v(TAG, "index=" + i);</pre>* that when you're building the string to pass into Log.d, the compiler uses a* StringBuilder and at least three allocations occur: the StringBuilder* itself, the buffer, and the String object. Realistically, there is also* another buffer allocation and copy, and even more pressure on the gc.* That means that if your log message is filtered out, you might be doing* significant work and incurring significant overhead.*/
public final class Log {/*** Priority constant for the println method; use Log.v.*/public static final int VERBOSE = 2;/*** Priority constant for the println method; use Log.d.*/public static final int DEBUG = 3;/*** Priority constant for the println method; use Log.i.*/public static final int INFO = 4;/*** Priority constant for the println method; use Log.w.*/public static final int WARN = 5;/*** Priority constant for the println method; use Log.e.*/public static final int ERROR = 6;/*** Priority constant for the println method.*/public static final int ASSERT = 7;/*** Exception class used to capture a stack trace in {@link #wtf()}.*/private static class TerribleFailure extends Exception {TerribleFailure(String msg, Throwable cause) { super(msg, cause); }}/*** Interface to handle terrible failures from {@link #wtf()}.** @hide*/public interface TerribleFailureHandler {void onTerribleFailure(String tag, TerribleFailure what);}private static TerribleFailureHandler sWtfHandler = new TerribleFailureHandler() {public void onTerribleFailure(String tag, TerribleFailure what) {RuntimeInit.wtf(tag, what);}};private Log() {}/*** Send a {@link #VERBOSE} log message.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.*/public static int v(String tag, String msg) {return println_native(LOG_ID_MAIN, VERBOSE, tag, msg);}/*** Send a {@link #VERBOSE} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @param tr An exception to log*/public static int v(String tag, String msg, Throwable tr) {return println_native(LOG_ID_MAIN, VERBOSE, tag, msg + '\n' + getStackTraceString(tr));}/*** Send a {@link #DEBUG} log message.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.*/public static int d(String tag, String msg) {return println_native(LOG_ID_MAIN, DEBUG, tag, msg);}/*** Send a {@link #DEBUG} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @param tr An exception to log*/public static int d(String tag, String msg, Throwable tr) {return println_native(LOG_ID_MAIN, DEBUG, tag, msg + '\n' + getStackTraceString(tr));}/*** Send an {@link #INFO} log message.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.*/public static int i(String tag, String msg) {return println_native(LOG_ID_MAIN, INFO, tag, msg);}/*** Send a {@link #INFO} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @param tr An exception to log*/public static int i(String tag, String msg, Throwable tr) {return println_native(LOG_ID_MAIN, INFO, tag, msg + '\n' + getStackTraceString(tr));}/*** Send a {@link #WARN} log message.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.*/public static int w(String tag, String msg) {return println_native(LOG_ID_MAIN, WARN, tag, msg);}/*** Send a {@link #WARN} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @param tr An exception to log*/public static int w(String tag, String msg, Throwable tr) {return println_native(LOG_ID_MAIN, WARN, tag, msg + '\n' + getStackTraceString(tr));}/*** Checks to see whether or not a log for the specified tag is loggable at the specified level.** The default level of any tag is set to INFO. This means that any level above and including* INFO will be logged. Before you make any calls to a logging method you should check to see* if your tag should be logged. You can change the default level by setting a system property:* 'setprop log.tag.<YOUR_LOG_TAG> <LEVEL>'* Where level is either VERBOSE, DEBUG, INFO, WARN, ERROR, ASSERT, or SUPPRESS. SUPPRESS will* turn off all logging for your tag. You can also create a local.prop file that with the* following in it:* 'log.tag.<YOUR_LOG_TAG>=<LEVEL>'* and place that in /data/local.prop.** @param tag The tag to check.* @param level The level to check.* @return Whether or not that this is allowed to be logged.* @throws IllegalArgumentException is thrown if the tag.length() > 23.*/public static native boolean isLoggable(String tag, int level);/** Send a {@link #WARN} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param tr An exception to log*/public static int w(String tag, Throwable tr) {return println_native(LOG_ID_MAIN, WARN, tag, getStackTraceString(tr));}/*** Send an {@link #ERROR} log message.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.*/public static int e(String tag, String msg) {return println_native(LOG_ID_MAIN, ERROR, tag, msg);}/*** Send a {@link #ERROR} log message and log the exception.* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @param tr An exception to log*/public static int e(String tag, String msg, Throwable tr) {return println_native(LOG_ID_MAIN, ERROR, tag, msg + '\n' + getStackTraceString(tr));}/*** What a Terrible Failure: Report a condition that should never happen.* The error will always be logged at level ASSERT with the call stack.* Depending on system configuration, a report may be added to the* {@link android.os.DropBoxManager} and/or the process may be terminated* immediately with an error dialog.* @param tag Used to identify the source of a log message.* @param msg The message you would like logged.*/public static int wtf(String tag, String msg) {return wtf(tag, msg, null);}/*** What a Terrible Failure: Report an exception that should never happen.* Similar to {@link #wtf(String, String)}, with an exception to log.* @param tag Used to identify the source of a log message.* @param tr An exception to log.*/public static int wtf(String tag, Throwable tr) {return wtf(tag, tr.getMessage(), tr);}/*** What a Terrible Failure: Report an exception that should never happen.* Similar to {@link #wtf(String, Throwable)}, with a message as well.* @param tag Used to identify the source of a log message.* @param msg The message you would like logged.* @param tr An exception to log. May be null.*/public static int wtf(String tag, String msg, Throwable tr) {TerribleFailure what = new TerribleFailure(msg, tr);int bytes = println_native(LOG_ID_MAIN, ASSERT, tag, msg + '\n' + getStackTraceString(tr));sWtfHandler.onTerribleFailure(tag, what);return bytes;}/*** Sets the terrible failure handler, for testing.** @return the old handler** @hide*/public static TerribleFailureHandler setWtfHandler(TerribleFailureHandler handler) {if (handler == null) {throw new NullPointerException("handler == null");}TerribleFailureHandler oldHandler = sWtfHandler;sWtfHandler = handler;return oldHandler;}/*** Handy function to get a loggable stack trace from a Throwable* @param tr An exception to log*/public static String getStackTraceString(Throwable tr) {if (tr == null) {return "";}// This is to reduce the amount of log spew that apps do in the non-error// condition of the network being unavailable.Throwable t = tr;while (t != null) {if (t instanceof UnknownHostException) {return "";}t = t.getCause();}StringWriter sw = new StringWriter();PrintWriter pw = new PrintWriter(sw);tr.printStackTrace(pw);return sw.toString();}/*** Low-level logging call.* @param priority The priority/type of this log message* @param tag Used to identify the source of a log message. It usually identifies* the class or activity where the log call occurs.* @param msg The message you would like logged.* @return The number of bytes written.*/public static int println(int priority, String tag, String msg) {return println_native(LOG_ID_MAIN, priority, tag, msg);}/** @hide */ public static final int LOG_ID_MAIN = 0;/** @hide */ public static final int LOG_ID_RADIO = 1;/** @hide */ public static final int LOG_ID_EVENTS = 2;/** @hide */ public static final int LOG_ID_SYSTEM = 3;/** @hide */ public static native int println_native(int bufID,int priority, String tag, String msg);
}
