Iat 381 Quiz 2

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

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

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

e.g. button, text

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

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

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

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

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

horizontal layout will not change the column

vertical layout will not change the row

when width/height is wrap_content

- can display large amounts of data

- manages data for displays on devices of various sizes

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)

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

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

- 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

asynchronous messages

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

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

intent filter

activity

service

broadcast receiver

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

startActivity(i);

ActivityTwo.class is its FULL java name

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

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

i.putExtra("key", value);

Intent i = new Intent(Intent.ACTION_VIEW);

web browser

if only one component found, it's started directly

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

which type of component the intent should be sent

for example activity or service

implicit intents

PackageManager.queryIntentActivities()

list of activities capable of handling the intent

if list is not empty, intent can be safely used

check when activity first starts

startActivityforResult(i, REQUEST_CODE) which is an intent method

identifies the intent

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

in void finish()

setResult(RESULT_OK, data);

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

RESULT_OK or RESULT_CANCELED

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

they are calculated

result of calculation from other sensors

rotation sensor is an example

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

create an instance of the sensor service

create an instance of a specific sensor

methods that let you determine sensor's capabilities

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

raw sensor data

type of sensor that generated event

accuracy of data

timestamp for event

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

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

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

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);

after getting system service:

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

// we have one

}

onAccuracyChanged()

onSensorChanged()

permissions

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

horizontal = top and bottom / row

vertical = right and left / column

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

AdapterView.OnItemClickListener();

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

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

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

2 = RESULT_OK or RESULT_CANCELED

3 = result data

public void finish(){

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

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

super.finish();

}

gives us information about the power of the system

helps us because it's crucial to use battery wisely

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

Fires an Intent in the future

check device network state

checks WIFI, GRPS and connection changes

- lists all the configured wifi connections

- scan for wifi network

- check/edit wi-fi connection