Android Activity Lifecycle Ch 3

Front 1

Three possible states of an activity in its lifecycle

Back 1

running, paused, stopped

Front 2

Methods that handle transitions and notify Activity of changes in its state

Back 2

onCreate(Bundle savedInstanceState)

onStart()

onResume()

onPause()

onStop()

onDestroy()

Front 3

Do you ever call onCreate or any Activity lifecycle methods yourself?

Back 3

No. You override them, and then Android will call them at the appropriate times

Front 4

What class sends log messages to a shared system-level log? What method will we use most often to log messages?

Back 4

android.util.Log

public static int d(String tag, String msg)

//d stands for "debug" --> refers to level of the log message

Front 5

public static int d(String tag, String msg);

describe the tag parameter and msg parameter (what they do, how to use them)

Back 5

TAG: TAG constant with classname as its value. Add private static final String TAG = "ClassName" to java file for class, and then override transition methods to add to log with a message

Front 6

Launching an app does what to an activity?

Back 6

creates, starts, and resumes

Front 7

Pressing the back button does what to an activity?

Back 7

pauses, stops, destroys

(tells Android you're exiting and not coming back)

Front 8

Pressing the home button does what to an activity?

Back 8

pauses, stops but tries not to destroy

(tells Android you're leaving but might come back. If the system needs more memory, it will be destroyed)

Front 9

Pressing the recent button after leaving does what to an activity?

Back 9

resumes and starts but does not create (as long as it wasn't destroyed)

Front 10

What states does the app transition through when you rotate a device?

Back 10

all of them. the old activity is paused, stopped, and destroyed, and a new one is created, started, and resumed

Front 11

device configuration

Back 11

set of characteristics that describes the current state of an individual device. includes screen orientation, screen density, screen size, keyboard type, dock mode, language, etc.

Front 12

What do applications typically do to match different device configurations?

Back 12

provide alternate resources. app will choose the appropriate resource. some resources can change at runtime (orientation) while others cannot (screen density)

Front 13

How do you create a landscape layout and a regular layout so that the app can choose based on orientation?

Back 13

create a new layout folder for orientation. copy the original xml file into the new layout folder, making sure it has the same name so it can be referenced with the same id, and make any necessary changes

Front 14

the -land suffix is an example of a

Back 14

configuration qualifier

Front 15

frame layout and gravity

Back 15

frame layout is the simplest layout. child views are arranged according to their gravity

Front 16

What does android do to activities whenever a runtime configuration change occurs?

Back 16

destroys the current activity and creates a new one

Front 17

How can you save data across a runtime configuration change?

Back 17

1. Add a constant in the activity class that will be the key for the key-value pair in the bundle

2. Override onSaveInstanceState(Bundle) to write the value along with its key

3. in onCreate(Bundle), check whether savedInstanceState is null. If not, then get the saved value

Front 18

What types can you save to and restore from a bundle?

Back 18

primitives

objects that implement serializable

Front 19

What happens when your activity is stashed?

Back 19

The activity was in the paused or stopped state. It no longer exists because Android needed more memory, but the activity record was saved in the OS

Front 20

When are activity records discarded?

Back 20

When the user presses the "back" button, on reboot, when it hasn't been used for a long time

Front 21

If you are overriding onSaveInstanceState(Bundle), how do you test on an emulator that the activity is being saved and restored as expected?

Back 21

Use the back button, or go to Settings > check "Don't keep activities"

Front 22

Five different log levels, each of which has a different priority

Back 22

error: Log.e

warning: Log.w

info: Log.i

debug: Log.d

verbose: Log.v

Front 23

What does this code do?

try {

question = mAnswerKey[mCurrentIndex];

} catch (ArrayIndexOutOfBoundsException ex) {

Log.e(TAG, "Index was out of bounds", ex);

}

Back 23

Logs a message at "error" log level, along with an exception stack trace