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Questions and Answers
What method in Android is called when a View is touched?
What method in Android is called when a View is touched?
- onTouch()
- onLongClick()
- onClick()
- onTouchEvent() (correct)
Which listener is used to detect click style events in Android?
Which listener is used to detect click style events in Android?
- onLongClickListener
- onClicklistener
- onTouchListener
- onClickListener (correct)
What is the purpose of the onLongClickListener in Android?
What is the purpose of the onLongClickListener in Android?
- To handle short click events
- To detect long touches on a View (correct)
- To handle multiple touch events
- To manage asynchronous tasks
How can a callback method for capturing click events be set for a Button in Android XML?
How can a callback method for capturing click events be set for a Button in Android XML?
Which interface in Android contains a single callback method for event handling?
Which interface in Android contains a single callback method for event handling?
What information is passed as arguments to a callback method?
What information is passed as arguments to a callback method?
What does a callback method returning true indicate?
What does a callback method returning true indicate?
In Android, what happens if a callback method returns false?
In Android, what happens if a callback method returns false?
Which callback method is called when a new key event occurs?
Which callback method is called when a new key event occurs?
What type of event triggers the callback method onTrackballEvent
?
What type of event triggers the callback method onTrackballEvent
?
What callback method is used to detect any form of contact with the touch screen, including individual or multiple touches and gesture motions?
What callback method is used to detect any form of contact with the touch screen, including individual or multiple touches and gesture motions?
Which event listener is triggered when a key on a device is pressed while a view has focus?
Which event listener is triggered when a key on a device is pressed while a view has focus?
What does the onFocusChangeListener detect in Android event handling?
What does the onFocusChangeListener detect in Android event handling?
Which callback method is used to listen for the creation of a context menu as the result of a long click?
Which callback method is used to listen for the creation of a context menu as the result of a long click?
In Android, what does the onLongClick() callback method receive as an argument?
In Android, what does the onLongClick() callback method receive as an argument?
What Android control type is used for a drop-down list that allows users to select one value from a set?
What Android control type is used for a drop-down list that allows users to select one value from a set?
Which Android control type is an on/off switch that can be toggled by the user?
Which Android control type is an on/off switch that can be toggled by the user?
For creating custom components in Android, what is the basic approach mentioned in the text?
For creating custom components in Android, what is the basic approach mentioned in the text?
Which Android control type is used for cases where only one option can be selected in a group, unlike checkboxes?
Which Android control type is used for cases where only one option can be selected in a group, unlike checkboxes?
What is the purpose of a Button control in Android?
What is the purpose of a Button control in Android?
What method allows a parent View to indicate that it should not intercept touch events?
What method allows a parent View to indicate that it should not intercept touch events?
Which method allows Activity to intercept all touch events before they are dispatched to the window?
Which method allows Activity to intercept all touch events before they are dispatched to the window?
What type of state is the appearance of the user interface before being committed to the app’s data model?
What type of state is the appearance of the user interface before being committed to the app’s data model?
In which method can an activity handle a configuration change without restarting?
In which method can an activity handle a configuration change without restarting?
Which method allows a ViewGroup to watch events as they are dispatched to child Views?
Which method allows a ViewGroup to watch events as they are dispatched to child Views?
What is the purpose of an event listener in Android?
What is the purpose of an event listener in Android?
How are events stored in the Android framework?
How are events stored in the Android framework?
What is the role of a callback method in Android event handling?
What is the role of a callback method in Android event handling?
Which class in Android contains event listener interfaces?
Which class in Android contains event listener interfaces?
Why is it necessary for a view to register an event listener in Android?
Why is it necessary for a view to register an event listener in Android?
What is the benefit of using ConstraintLayout in Android?
What is the benefit of using ConstraintLayout in Android?
Which tool in Android Studio is tightly integrated with ConstraintLayout?
Which tool in Android Studio is tightly integrated with ConstraintLayout?
In a dynamic layout scenario, what is used to populate the layout with views at runtime?
In a dynamic layout scenario, what is used to populate the layout with views at runtime?
What role does an Adapter play in Android layouts backed by it?
What role does an Adapter play in Android layouts backed by it?
Which components are considered input controls in Android apps?
Which components are considered input controls in Android apps?
How is an input control usually added to an Android XML layout?
How is an input control usually added to an Android XML layout?
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Study Notes
Touch Events
onTouchEvent()
is the method called when a View is touched.OnClickListener
is used to detect click-style events.onLongClickListener
detects long presses.- A callback method for click events can be set in XML for a Button using
android:onClick
attribute.
Event Handling Interfaces and Callbacks
View.OnClickListener
interface contains a single callback method for event handling.- Callback methods receive arguments such as View.
- Returning
true
from a callback method indicates that the event has been handled. - If a callback method returns
false
, the event is passed to the next listener in the chain.
Key Events and Touchscreen Interactions
onKeyDown
andonKeyUp
are called when a new key event occurs.onTrackballEvent
is triggered by a trackball event.onTouchEvent
detects all forms of touch screen contact, including single and multiple touches and gestures.
Focus and Context Menu Events
onFocusChangeListener
detects focus changes for a View.onCreateContextMenu
is called when a long click creates a context menu.onLongClick()
receives aView
argument.
Android Controls
Spinner
is a drop-down list for selecting one value.Switch
is an on/off toggle.- Creating custom components often involves extending
View
class. RadioGroup
is used for groups where only one option can be selected.Button
triggers an action when clicked.
ViewGroup Events and State Management
requestDisallowInterceptTouchEvent
allows a parent View to prevent intercepting touch events.dispatchTouchEvent
lets an Activity intercept all touch events before they reach the window.- The appearance of the user interface before being committed to the data model is called the
transient state
. onConfigurationChanged
handles configuration changes without restarting the activity.onInterceptTouchEvent
allows a ViewGroup to observe touch events dispatched to child views.
Event Listener Fundamentals
- Event listeners respond to specific events in Android apps.
- Events are stored in the Android framework using a
MessageQueue
. - A callback method is executed in response to a specific event.
View
class contains event listener interfaces.- Views must register event listeners to receive event notifications.
Layout and Adapter
ConstraintLayout
is a highly efficient layout system in Android.- The
Layout Editor
in Android Studio is designed for ConstraintLayout. - Dynamic layouts can be populated with views at runtime using
LayoutInflater
. - An
Adapter
manages the interaction between the layout and the underlying data source.
Input Controls
- Input controls, like buttons and text fields, allow user interaction.
- They are typically added to a layout using
android:layout_
attributes in the XML file.
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