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Added in API level 1

Log

public final class Log
extends Object

java.lang.Object
   ↳ android.util.Log


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, Throwable tr)

Send a DEBUG log message and log the exception.

static int d(String tag, String msg)

Send a DEBUG log message.

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, Throwable tr)

Send a INFO log message and log the exception.

static int i(String tag, String msg)

Send an INFO log message.

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, String msg)

What a Terrible Failure: Report a condition that should never happen.

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, Throwable tr)

What a Terrible Failure: Report an exception that should never happen.

Inherited methods

From class java.lang.Object

Constants

ASSERT

Added in API level 1
int ASSERT

Priority constant for the println method.

Constant Value: 7 (0x00000007)

DEBUG

Added in API level 1
int DEBUG

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

Constant Value: 3 (0x00000003)

ERROR

Added in API level 1
int ERROR

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

Constant Value: 6 (0x00000006)

INFO

Added in API level 1
int INFO

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

Constant Value: 4 (0x00000004)

VERBOSE

Added in API level 1
int VERBOSE

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

Constant Value: 2 (0x00000002)

WARN

Added in API level 1
int WARN

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

Constant Value: 5 (0x00000005)

Public methods

d

Added in API level 1
int d (String tag, 
                String msg, 
                Throwable tr)

Send a DEBUG log message and log the exception.

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

d

Added in API level 1
int d (String tag, 
                String msg)

Send a DEBUG log message.

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

e

Added in API level 1
int e (String tag, 
                String msg)

Send an ERROR log message.

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

e

Added in API level 1
int e (String tag, 
                String msg, 
                Throwable tr)

Send a ERROR log message and log the exception.

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

getStackTraceString

Added in API level 1
String getStackTraceString (Throwable tr)

Handy function to get a loggable stack trace from a Throwable

Parameters
tr Throwable: An exception to log
Returns
String

i

Added in API level 1
int i (String tag, 
                String msg, 
                Throwable tr)

Send a INFO log message and log the exception.

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

i

Added in API level 1
int i (String tag, 
                String msg)

Send an INFO log message.

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

isLoggable

Added in API level 1
boolean isLoggable (String tag, 
                int level)

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

println

Added in API level 1
int println (int priority, 
                String tag, 
                String msg)

Low-level logging call.

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

v

Added in API level 1
int v (String tag, 
                String msg)

Send a VERBOSE log message.

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

v

Added in API level 1
int v (String tag, 
                String msg, 
                Throwable tr)

Send a VERBOSE log message and log the exception.

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

w

Added in API level 1
int w (String tag, 
                Throwable tr)

Parameters
tag String
tr Throwable
Returns
int

w

Added in API level 1
int w (String tag, 
                String msg, 
                Throwable tr)

Send a WARN log message and log the exception.

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

w

Added in API level 1
int w (String tag, 
                String msg)

Send a WARN log message.

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

wtf

Added in API level 8
int wtf (String tag, 
                String msg)

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 String: Used to identify the source of a log message.
msg String: The message you would like logged.
Returns
int

wtf

Added in API level 8
int wtf (String tag, 
                Throwable tr)

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

Parameters
tag String: Used to identify the source of a log message.
tr Throwable: An exception to log.
Returns
int

wtf

Added in API level 8
int wtf (String tag, 
                String msg, 
                Throwable tr)

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

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