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Android APIs
public final class

Log

extends Object
java.lang.Object
   ↳ android.util.Log

Class Overview

API for sending log output.

Generally, use the Log.v() Log.d() Log.i() Log.w() and Log.e() methods.

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.

Tip: A good convention is to declare a TAG constant in your class: 

        private static final String TAG = "MyActivity";
and use that in subsequent calls to the log methods.

Tip: Don't forget that when you make a call like 

        Log.v(TAG, "index=" + i);
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.

Summary

Constants
int ASSERT Priority constant for the println method.
int DEBUG Priority constant for the println method; use Log.d.
int ERROR Priority constant for the println method; use Log.e.
int INFO Priority constant for the println method; use Log.i.
int VERBOSE Priority constant for the println method; use Log.v.
int WARN Priority constant for the println method; use Log.w.
Public Methods
static int d ( String tag, String msg)
Send a DEBUG log message.
static int d ( String tag, String msg, Throwable tr)
Send a DEBUG log message and log the exception.
static int e ( String tag, String msg)
Send an ERROR log message.
static int e ( String tag, String msg, Throwable tr)
Send a ERROR log message and log the exception.
static String getStackTraceString ( Throwable tr)
Handy function to get a loggable stack trace from a Throwable
static int i ( String tag, String msg)
Send an INFO log message.
static int i ( String tag, String msg, Throwable tr)
Send a INFO log message and log the exception.
static boolean isLoggable ( String tag, int level)
Checks to see whether or not a log for the specified tag is loggable at the specified level.
static int println (int priority, String tag, String msg)
Low-level logging call.
static int v ( String tag, String msg)
Send a VERBOSE log message.
static int v ( String tag, String msg, Throwable tr)
Send a VERBOSE log message and log the exception.
static int w ( String tag, Throwable tr)
static int w ( String tag, String msg, Throwable tr)
Send a WARN log message and log the exception.
static int w ( String tag, String msg)
Send a WARN log message.
static int wtf ( String tag, Throwable tr)
What a Terrible Failure: Report an exception that should never happen.
static int wtf ( String tag, String msg)
What a Terrible Failure: Report a condition that should never happen.
static int wtf ( String tag, String msg, Throwable tr)
What a Terrible Failure: Report an exception that should never happen.
[Expand]
Inherited Methods
From class java.lang.Object

Constants

public static final int ASSERT

Added in API level 1

Priority constant for the println method.

Constant Value: 7 (0x00000007)

public static final int DEBUG

Added in API level 1

Priority constant for the println method; use Log.d.

Constant Value: 3 (0x00000003)

public static final int ERROR

Added in API level 1

Priority constant for the println method; use Log.e.

Constant Value: 6 (0x00000006)

public static final int INFO

Added in API level 1

Priority constant for the println method; use Log.i.

Constant Value: 4 (0x00000004)

public static final int VERBOSE

Added in API level 1

Priority constant for the println method; use Log.v.

Constant Value: 2 (0x00000002)

public static final int WARN

Added in API level 1

Priority constant for the println method; use Log.w.

Constant Value: 5 (0x00000005)

Public Methods

public static int d ( String tag, String msg)

Added in API level 1

Send a DEBUG log message.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.

public static int d ( String tag, String msg, Throwable tr)

Added in API level 1

Send a DEBUG log message and log the exception.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
tr An exception to log

public static int e ( String tag, String msg)

Added in API level 1

Send an ERROR log message.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.

public static int e ( String tag, String msg, Throwable tr)

Added in API level 1

Send a ERROR log message and log the exception.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
tr An exception to log

public static String getStackTraceString ( Throwable tr)

Added in API level 1

Handy function to get a loggable stack trace from a Throwable

Parameters
tr An exception to log

public static int i ( String tag, String msg)

Added in API level 1

Send an INFO log message.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.

public static int i ( String tag, String msg, Throwable tr)

Added in API level 1

Send a INFO log message and log the exception.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
tr An exception to log

public static boolean isLoggable ( String tag, int level)

Added in API level 1

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.

Parameters
tag The tag to check.
level The level to check.
Returns
  • Whether or not that this is allowed to be logged.
Throws
IllegalArgumentException is thrown if the tag.length() > 23.

public static int println (int priority, String tag, String msg)

Added in API level 1

Low-level logging call.

Parameters
priority The priority/type of this log message
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
Returns
  • The number of bytes written.

public static int v ( String tag, String msg)

Added in API level 1

Send a VERBOSE log message.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.

public static int v ( String tag, String msg, Throwable tr)

Added in API level 1

Send a VERBOSE log message and log the exception.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
tr An exception to log

public static int w ( String tag, Throwable tr)

Added in API level 1

public static int w ( String tag, String msg, Throwable tr)

Added in API level 1

Send a WARN log message and log the exception.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.
tr An exception to log

public static int w ( String tag, String msg)

Added in API level 1

Send a WARN log message.

Parameters
tag Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
msg The message you would like logged.

public static int wtf ( String tag, Throwable tr)

Added in API level 8

What a Terrible Failure: Report an exception that should never happen. Similar to wtf(String, String) , with an exception to log.

Parameters
tag Used to identify the source of a log message.
tr An exception to log.

public static int wtf ( String tag, String msg)

Added in API level 8

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 DropBoxManager and/or the process may be terminated immediately with an error dialog.

Parameters
tag Used to identify the source of a log message.
msg The message you would like logged.

public static int wtf ( String tag, String msg, Throwable tr)

Added in API level 8

What a Terrible Failure: Report an exception that should never happen. Similar to wtf(String, Throwable) , with a message as well.

Parameters
tag Used to identify the source of a log message.
msg The message you would like logged.
tr An exception to log. May be null.