When you use the android.util.Log class to send log messages, you control not only the content of a message but also a level that specifies how important the message is. Android supports five log levels, shown in Table 3.2. Each level has a corresponding function in the Log class. Sending output to the log is as simple as calling the corresponding Log function.
Table 3.2 Log levels and functions
| Log level | Function | Used for |
|---|---|---|
|
ERROR |
Log.e(…) |
errors |
|
WARNING |
Log.w(…) |
warnings |
|
INFO |
Log.i(…) |
informational messages |
|
DEBUG |
Log.d(…) |
debug output (may be filtered out) |
|
VERBOSE |
Log.v(…) |
development only |
In addition, each of the logging functions has two signatures: one that takes a TAG string and a message string, and a second that takes those two arguments plus an instance of Throwable, which makes it easy to log information about a particular exception that your application might throw. Listing 3.5 shows some sample log function signatures.
Listing 3.5 Different ways of logging in Android
// Log a message at DEBUG log level
Log.d(TAG, "Current question index: $currentIndex")
try {
val question = questionBank[currentIndex]
} catch (ex: ArrayIndexOutOfBoundsException) {
// Log a message at ERROR log level, along with an exception stack trace
Log.e(TAG, "Index was out of bounds", ex)
}