Package android.util

Class Log

java.lang.Object

android.util.Log

public final class Log
extends Object

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Log.TerribleFailureHandler	Interface to handle terrible failures from wtf(java.lang.String, java.lang.String).

Field Summary

Fields

Modifier and Type	Field	Description
static int	ASSERT	Priority constant for the println method.
static int	DEBUG	Priority constant for the println method; use Log.d.
static int	ERROR	Priority constant for the println method; use Log.e.
static int	INFO	Priority constant for the println method; use Log.i.
static int	LOG_ID_CRASH
static int	LOG_ID_EVENTS
static int	LOG_ID_MAIN
static int	LOG_ID_RADIO
static int	LOG_ID_SYSTEM
static int	VERBOSE	Priority constant for the println method; use Log.v.
static int	WARN	Priority constant for the println method; use Log.w.

Method Summary

Modifier and Type	Method	Description
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	println_native(int bufID, int priority, String tag, String msg)
static Log.TerribleFailureHandler	setWtfHandler(Log.TerribleFailureHandler handler)	Sets the terrible failure handler, for testing.
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, String msg)	Send a WARN log message.
static int	w(String tag, String msg, Throwable tr)	Send a WARN log message and log the exception.
static int	w(String tag, Throwable tr)
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.
static int	wtf(String tag, Throwable tr)	What a Terrible Failure: Report an exception that should never happen.
static int	wtfStack(String tag, String msg)	Like wtf(String, String), but also writes to the log the full call stack.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

VERBOSE

public static final int VERBOSE

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

See Also:

Constant Field Values

DEBUG

public static final int DEBUG

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

See Also:

Constant Field Values

INFO

public static final int INFO

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

See Also:

Constant Field Values

WARN

public static final int WARN

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

See Also:

Constant Field Values

ERROR

public static final int ERROR

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

See Also:

Constant Field Values

ASSERT

public static final int ASSERT

Priority constant for the println method.

See Also:

Constant Field Values

LOG_ID_MAIN

public static final int LOG_ID_MAIN

See Also:

Constant Field Values

LOG_ID_RADIO

public static final int LOG_ID_RADIO

See Also:

Constant Field Values

LOG_ID_EVENTS

public static final int LOG_ID_EVENTS

See Also:

Constant Field Values

LOG_ID_SYSTEM

public static final int LOG_ID_SYSTEM

See Also:

Constant Field Values

LOG_ID_CRASH

public static final int LOG_ID_CRASH

See Also:

Constant Field Values

Method Detail

v

public static int v(String tag,
                    String msg)

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.

v

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

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

d

public static int d(String tag,
                    String msg)

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.

d

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

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

i

public static int i(String tag,
                    String msg)

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.

i

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

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

w

public static int w(String tag,
                    String msg)

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.

w

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

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

isLoggable

public 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. 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.

w

public static int w(String tag,
                    Throwable tr)

e

public static int e(String tag,
                    String msg)

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.

e

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

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

wtf

public static 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 android.os.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.

wtfStack

public static int wtfStack(String tag,
                           String msg)

Like wtf(String, String), but also writes to the log the full call stack.

wtf

public static 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 - Used to identify the source of a log message.

tr - An exception to log.

wtf

public static 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 - Used to identify the source of a log message.

msg - The message you would like logged.

tr - An exception to log. May be null.

setWtfHandler

public static Log.TerribleFailureHandler setWtfHandler(Log.TerribleFailureHandler handler)

Sets the terrible failure handler, for testing.

Returns:

the old handler

getStackTraceString

public static String getStackTraceString(Throwable tr)

Handy function to get a loggable stack trace from a Throwable

Parameters:

tr - An exception to log

println

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

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.

println_native

public static int println_native(int bufID,
                                 int priority,
                                 String tag,
                                 String msg)