Mobile Application Development
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The document outlines key concepts in Android event handling, focusing on event listeners and handlers, which are crucial for user interactions with UI components. It details specific methods such as OnClickListener, OnLongClickListener, and OnFocusChangeListener, explaining how each is triggered by user actions. Additionally, it briefly discusses the ListView as a means to display items in a vertically scrolling format.
Mobile Application Development
- 1. MOBILE APPLICATION DEVELOPMENT LECTURE – 05 By: AbuBakar Ubaid
- 2. EVENT HANDLING By: AbuBakar Ubaid
- 3. Android - Event Handling • Event Listeners − An event listener is an interface in the View class that contains a single callback method.These methods will be called by the Android framework when the View to which the listener has been registered is triggered by user interaction with the item in the UI. • Event Listeners Registration − Event Registration is the process by which an Event Handler gets registered with an Event Listener so that the handler is called when the Event Listener fires the event. • Event Handlers − When an event happens and we have registered an event listener for the event, the event listener calls the Event Handlers, which is the method that actually handles the event. 3
- 4. OnClickListener() and onClick() //---Button view--- Button btnOpen = (Button) findViewById(R.id.btnOpen); btnOpen.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { DisplayToast(“You have clicked the Open button”); } }); 4
- 5. Event Handler Event Listener & Description onClick() OnClickListener() This is called when the user either clicks or touches or focuses upon any widget like button, text, image etc. You will use onClick() event handler to handle such event. onLongClick() OnLongClickListener() This is called when the user either clicks or touches or focuses upon any widget like button, text, image etc. for one or more seconds. You will use onLongClick() event handler to handle such event. onFocusChange() OnFocusChangeListener() This is called when the widget looses its focus ie. user goes away from the view item. You will use onFocusChange() event handler to handle such event. onKey() OnFocusChangeListener() This is called when the user is focused on the item and presses or releases a hardware key on the device. You will use onKey() event handler to handle such event. 5
- 6. 6 Event Handler Event Listener & Description onTouch() OnTouchListener() This is called when the user presses the key, releases the key, or any movement gesture on the screen. You will use onTouch() event handler to handle such event. onMenuItemClick() OnMenuItemClickListener() This is called when the user selects a menu item. You will use onMenuItemClick() event handler to handle such event. onCreateContextMenu() onCreateContextMenuItemListener() This is called when the context menu is being built(as the result of a sustained "long click)
- 7. LIST VIEW By: AbuBakar Ubaid
- 8. ListView View • The ListView displays a list of items in a vertically scrolling list. 8
- 9. THANK YOU LECTURE – 05 “Event Handling & List View” By: AbuBakar Ubaid