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Designing user interfaces using: Simple views

Designing user interfaces using: Simple views. Views. Basic views TextView EditText Button ImageButton CheckBox ToggleButton RadioButton RadioGroup Spinner. Pickers TimePicker DatePicker Normally added to DialogFragment Lists ListView ListActivity ListFragment. View definition.

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Designing user interfaces using: Simple views

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  1. Designing user interfaces using: Simple views Designing user interfaces using: Simple views

  2. Views • Basic views • TextView • EditText • Button • ImageButton • CheckBox • ToggleButton • RadioButton • RadioGroup • Spinner • Pickers • TimePicker • DatePicker • Normally added to DialogFragment • Lists • ListView • ListActivity • ListFragment Designing user interfaces using: Simple views

  3. View definition • Views a usually defined in an XML file • Declarative • Example: res/layout/main.xml • Always in the folder res/layout • Each activity typically has one (or more) layout XML files. • Views can be defined in the Activity • Programmatically • This is not the usual way • Useful if you want a dynamic number of Views • Example: Quiz game where each question has a different number of possible answers • More on this later … Designing user interfaces using: Simple views

  4. Writing the view definition XML file • The layout XML file can be written in two ways • Pure XML • Graphical drag-and-drop GUI builder • The two ways can mixed Designing user interfaces using: Simple views

  5. View configuration • Some configuration can be done in the layout XML file • Width, height, etc. • Some configuration must be done in the Activity Java class • Programming event handlers • OnSomethingClicked(View …) etc. • Loading data into advanced views like lists Designing user interfaces using: Simple views

  6. Event handlers:Android vs. Windows forms Android Windows event handlers, etc. Every GUI component can have any number of event handlers of a certain type Usually 0 or 1, though Syntax Obj.event += eventHandler Observer design pattern Event handlers listen for changes in the GUI component Adding / removing listeners at runtime • Every GUI component has ONE event handler of a certain type • Strategy design pattern • GUI component calls the event handler to handle the event • Changing strategy at runtime Designing user interfaces using: Simple views

  7. Registering events for a view • Buttons etc. Can register event handlers • btn.setOnClickListener(btnListener); • Often using anonymous inner classes btn.setOnClickListener(new OnClickListener() { public void onClick(View v) { // do something } }); • Examples: ClickEventHandling project Android user interfaces using layouts

  8. Listening for User Interface notifications • When you press a key the view in focus will try to handle the event • Example: EditText handles left + right arrows, but not up + down arrows • Unhandled events are passed to the Activity • public booleanonKey(…) • Returned boolean value • True: The event handling has finished • False: The event handling has not finished • Example: ClickEventHandling Android user interfaces using layouts

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