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58 Cards in this Set

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what 3 steps event-wise happen when a button is clicked in android?

1. button clicked

2. android system receives the event

3. only the LISTENER is interested in reacting to the event

e.g. when the doorbell rings, everyone hears it, but only the person interested runs to the door

what are the 4 steps to implement button click?

1. tell android system we're interested in listening to button click

- implement onClickListener

2. retrieve button from xml into java code

- findViewById

3. tell java we're listening to button being clicked

- button.setOnClickListener(this);

4. what should happen when button is clicked

- in the onClick method

what is a view? what's an example?

object that occupies a rectangular area on screen is responsible for handling events

e.g. button, text

what is a view group? what are its different types of structures?

occupies rectangular area on screen, is invisible and holds other views in a certain structure (vertically, horizontally, grid)

what is the root view? in the root view, what should the width and height be set to?

the top-level ViewGroup that holds all the other ViewGroups/Views

width/height should be match parent to fill up all available space

when you assign a layout_weight to 1, what does it do to the other elements that have layout_weight of 0?

the ones with 0 take up only the space it NEEDS, and heavier one will take up the rest of the space

what's the difference between layout_gravity and gravity?

layout_gravity controls the place where the VIEW is situated in the layout (inside the parent)

gravity controls where the CONTENT of the view (inside) should appear inside the view -> e.g. how the text is aligned in the component

for layout_gravity:

horizontal layout will not change the ___

vertical layout will not change the ___

horizontal layout will not change the column

vertical layout will not change the row

when does gravity attribute doesn't really work, in terms of its width and height?

when width/height is wrap_content

what are 2 advantages of a listview?

- can display large amounts of data

- manages data for displays on devices of various sizes

what are the 3 concepts of ListView?

1. large amount of data (data source e.g. array, database)

2. class to manage the data (ListAdapter)

3. class to manage the appearance (ListView)

what does ListAdapter do?

takes item from data source and create a view out of it

e.g. text view, image and a text view

what does the adapter in android do? what are examples of adapters?

- responsible for managing the data

- adapter accesses the data and displays it in a view

different types of adapters

- array adapter

- cursor adapter (database)

- base adapter (custom data

what are intents? what do they allow?

asynchronous messages

allow android components to request functionality from other components of the android system, AND other activities in the app

what's another function of intents other than its main?

can also be used to single system that a certain event has occured

how can other components register to an event, to know if a certain event has occurred?

intent filter

what are 3 examples of components that intents can communicate with, and send data, and receive responses?



broadcast receiver

how to send an intent to the system to start aNOTHER activity? 2 lines of code

Intent i = new Intent(this, ActivityTwo.class);


ActivityTwo.class is its FULL java name

what are the two types of intents?

explicit intent = defining the component which should be called by android system, using java class identifier

implicit intent = specify action which should be performed and can start ANY component that can handle the intended action

-> action is a filter

why would you use an implicit intent? give an example

in the app, if you want to send an email, specify the ACTION and leave it up to the system that can do that functionality

another example: google maps

how to send data with explicit intents? code

i.putExtra("key", value);

what's the line of code to start an implicit intent?

Intent i = new Intent(Intent.ACTION_VIEW);

what's a typical thing that's registered to Intent.ACTION_VIEW?

web browser

what happens after the android system searches for the components that are registered for an action, when you do implicit intents?

if only one component found, it's started directly

if there's several components, user will get selection dialog

when you send an intent to the android system, what do you need to specify?

which type of component the intent should be sent

for example activity or service

what intent is used when you send a user to another app?

implicit intents

how to verify there is an app to receive your intent?


what does queryIntentActivities() return? when should you do this check?

list of activities capable of handling the intent

if list is not empty, intent can be safely used

check when activity first starts

which method to retrieve result data from the started activity?

startActivityforResult(i, REQUEST_CODE) which is an intent method

what does REQUEST_CODE do? why is it important?

identifies the intent

important if you're making an intent for more than one activity

how to return data to the initial activity that made an intent for you?

in void finish()

setResult(RESULT_OK, data);

data parameter is the bundle of data that you putExtra() things into

what is result code?


what are 3 categories of sensors? give examples

motion sensors

e.g. accerometer, gravity sensor, rotational sensor

environmental sensors

e.g. air temperature sensors, pressure, light

position sensors

e.g. physical position, orientation

what are virtual sensors? what's an example

they are calculated

result of calculation from other sensors

rotation sensor is an example

what are 5 guidelines when accessing hardware

1. no assumption that hardware exist

2. always check and verify optional features

3. exception handling and errors

4. return value checking

5. hardware features are device resources, so:

- acquire late, release early

- don't drain battery by misusing hardware resources

what does the SensorManager class do?

create an instance of the sensor service

what does the Sensor class do? what does it provide?

create an instance of a specific sensor

methods that let you determine sensor's capabilities

what does the SensorEvent class do? what does an sensor event object incude?

system uses this class to create sensor event object which provides info about a sensor event

what does an sensor event object include? 4 things

raw sensor data

type of sensor that generated event

accuracy of data

timestamp for event

what sensorEventListener interface do?

use this interface to create two callback methods that receive notifications (sensor events) when sensor values change

what are 2 sensor related tasks?

identifying sensors and sensor capabilities

- disable app features that use sensors that are not present on device

- identify all sensors of a given type and choose one with optimum performance for app

monitor sensor events

- acquiring sensor data (event_ every time sensor detects change

- gets the things from sensor event object

what are the 4 steps when working with sensors?

1. see what sensors are available on device

2. determine sensor's capabilities (e.g. max range, power requirements, etc.)

3. acquire raw sensor data and define minimum rate where you acquire data

4. register and unregister sensor event listeners that monitor sensor changes

when we identify sensors and capabilities, how do we do that in the code? 2 steps

get instance of sensormanager

private SensorManager mSensorManager;

mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

get list of all sensors on the devices

List deviceSensors = mSensorManager.getSensorList(Sensor.TYPE_ALL);

how to check for a certain sensor in code?

after getting system service:

if(mSensoranager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD) != null) {

// we have one


what are the two methods from SensorEventListener interface?



what do you have to put in manifest to use services like power service, vibration service, etc.?


when do you need to set layout_width to be 0? what about layout_height to 0?

when you use layout_weight in a view inside a horizontal linearlayout, set layout_width to 0

when you use layout_weight in a view inside a vertical linearlayout, set layout_height to 0

in horizontal linearlayouts, ___ and ___ directions work for layout_gravity

in vertical linearlayouts, ___ and ___ directions work for layout_gravity

horizontal = top and bottom / row

vertical = right and left / column

what does an adapter look like in code?

ArrayAdapter adapter = new ArrayAdapter(this, androidlayoutthing, datasource);

what interface do you have to implement when you want to use listviews?


what method comes with the OnItemClickListener interface, what are the parameters, and what do you do with it?

onItemClick(AdapterView<?>parent, View view, int position, long id);

1 = listview parent

2 = view that was clicked (textview)

3 = row of view that was clicked, starting from 0

4 = id of data

what method is called (in activity1) when activity2 sends back its results to activity1?

onActivityResult(int requestCode, int resultCode, Intent data);

1 = requestCode identifies which activity, it was passed to startActivityForResult()


3 = result data

in activity2, how do you send results back to activity1? what is the method and what is the actual method where you set the result?

public void finish(){

Intent data = new Intent(); data.putExtra("returnKey1", ”This is the result");

// Activity finished ok, return the datasetResult(RESULT_OK, data);



what does the power service give us? how does that help us?

gives us information about the power of the system

helps us because it's crucial to use battery wisely

with services such as power, wifi, telephony etc, what is the line of code to use them?

SomethingManager manager = (SomethingManager) getSystemService(Context.SOMETHING_SERVICE);

what does the alarm service do?

Fires an Intent in the future

what does connectivity service do? what 2 things does it check?

check device network state

checks WIFI, GRPS and connection changes

what can wifi service do? 3 things

- lists all the configured wifi connections

- scan for wifi network

- check/edit wi-fi connection