Added in API level 1

Log

---

Kotlin |Java

class Log

kotlin.Any
↳	android.util.Log

API for sending log output.

Generally, you should use the #v, #d, #i, #w, and #e methods to write logs. You can then view the logs in logcat.

The order in terms of verbosity, from least to most is ERROR, WARN, INFO, DEBUG, VERBOSE.

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.

When calling the log methods that take a Throwable parameter, if any of the throwables in the cause chain is an UnknownHostException, then the stack trace is not logged.

Note: The return value from the logging functions in this class may vary between Android releases due to changes in the logging implementation. For the methods that return an integer, a positive value may be considered as a successful invocation.

Summary

Constants
static Int	ASSERT Priority constant for the println method.
static Int	DEBUG Priority constant for the println method; use Log.
static Int	ERROR Priority constant for the println method; use Log.
static Int	INFO Priority constant for the println method; use Log.
static Int	VERBOSE Priority constant for the println method; use Log.
static Int	WARN Priority constant for the println method; use Log.

Public methods
static Int	d(tag: String?, msg: String) Send a DEBUG log message.
static Int	d(tag: String?, msg: String?, tr: Throwable?) Send a DEBUG log message and log the exception.
static Int	e(tag: String?, msg: String) Send an ERROR log message.
static Int	e(tag: String?, msg: String?, tr: Throwable?) Send a ERROR log message and log the exception.
static String	getStackTraceString(tr: Throwable?) Handy function to get a loggable stack trace from a Throwable
static Int	i(tag: String?, msg: String) Send an INFO log message.
static Int	i(tag: String?, msg: String?, tr: Throwable?) Send a INFO log message and log the exception.
static Boolean	isLoggable(tag: String?, level: Int) Checks to see whether or not a log for the specified tag is loggable at the specified level.
static Int	println(priority: Int, tag: String?, msg: String) Low-level logging call.
static Int	v(tag: String?, msg: String) Send a VERBOSE log message.
static Int	v(tag: String?, msg: String?, tr: Throwable?) Send a VERBOSE log message and log the exception.
static Int	w(tag: String?, msg: String) Send a WARN log message.
static Int	w(tag: String?, msg: String?, tr: Throwable?) Send a WARN log message and log the exception.
static Int	w(tag: String?, tr: Throwable?) Send a WARN log message and log the exception.
static Int	wtf(tag: String?, msg: String?) What a Terrible Failure: Report a condition that should never happen.
static Int	wtf(tag: String?, tr: Throwable) What a Terrible Failure: Report an exception that should never happen.
static Int	wtf(tag: String?, msg: String?, tr: Throwable?) What a Terrible Failure: Report an exception that should never happen.

Constants

ASSERT

Added in API level 1

static val ASSERT: Int

Priority constant for the println method.

Value: 7

DEBUG

Added in API level 1

static val DEBUG: Int

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

Value: 3

ERROR

Added in API level 1

static val ERROR: Int

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

Value: 6

INFO

Added in API level 1

static val INFO: Int

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

Value: 4

VERBOSE

Added in API level 1

static val VERBOSE: Int

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

Value: 2

WARN

Added in API level 1

static val WARN: Int

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

Value: 5

Public methods

d

Added in API level 1

static fun d(
    tag: String?, 
    msg: String
): Int

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. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

d

Added in API level 1

static fun d(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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. This value may be null.
msg	String?: The message you would like logged. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

e

Added in API level 1

static fun e(
    tag: String?, 
    msg: String
): Int

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. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

e

Added in API level 1

static fun e(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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. This value may be null.
msg	String?: The message you would like logged. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

getStackTraceString

Added in API level 1

static fun getStackTraceString(tr: Throwable?): String

Handy function to get a loggable stack trace from a Throwable

If any of the throwables in the cause chain is an UnknownHostException, this returns an empty string.

Parameters
tr	Throwable?: An exception to log. This value may be null.

Return
String	This value cannot be null.

i

Added in API level 1

static fun i(
    tag: String?, 
    msg: String
): Int

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. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

i

Added in API level 1

static fun i(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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. This value may be null.
msg	String?: The message you would like logged. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

isLoggable

Added in API level 1

static fun isLoggable(
    tag: String?, 
    level: Int
): Boolean

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, or ASSERT. 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. This value may be null.
level	Int: The level to check. Value is android.util.Log#ASSERT, android.util.Log#ERROR, android.util.Log#WARN, android.util.Log#INFO, android.util.Log#DEBUG, or android.util.Log#VERBOSE

Return
Boolean	Whether or not that this is allowed to be logged.

Exceptions
java.lang.IllegalArgumentException	is thrown if the tag.length() > 23 for Nougat (7.0) and prior releases (API <= 25), there is no tag limit of concern after this API level.

println

Added in API level 1

static fun println(
    priority: Int, 
    tag: String?, 
    msg: String
): Int

Low-level logging call.

Parameters
priority	Int: The priority/type of this log message Value is android.util.Log#ASSERT, android.util.Log#ERROR, android.util.Log#WARN, android.util.Log#INFO, android.util.Log#DEBUG, or android.util.Log#VERBOSE
tag	String?: Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

v

Added in API level 1

static fun v(
    tag: String?, 
    msg: String
): Int

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. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

v

Added in API level 1

static fun v(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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. This value may be null.
msg	String?: The message you would like logged. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

w

Added in API level 1

static fun w(
    tag: String?, 
    msg: String
): Int

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. This value may be null.
msg	String: The message you would like logged. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

w

Added in API level 1

static fun w(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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. This value may be null.
msg	String?: The message you would like logged. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

w

Added in API level 1

static fun w(
    tag: String?, 
    tr: Throwable?
): Int

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. This value may be null.
tr	Throwable?: An exception to log. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

wtf

Added in API level 8

static fun wtf(
    tag: String?, 
    msg: String?
): Int

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 android.os.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. This value may be null.
msg	String?: The message you would like logged. This value may be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

wtf

Added in API level 8

static fun wtf(
    tag: String?, 
    tr: Throwable
): Int

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

Parameters
tag	String?: Used to identify the source of a log message. This value may be null.
tr	Throwable: An exception to log. This value cannot be null.

Return
Int	A positive value if the message was loggable (see isLoggable).

wtf

Added in API level 8

static fun wtf(
    tag: String?, 
    msg: String?, 
    tr: Throwable?
): Int

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

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

Return
Int	A positive value if the message was loggable (see isLoggable).