[Android] Lec02

Button(link)

android:clickable='bool' : set to false to disable the button

android:id="@+id/theID" : unique ID for use in Java code

android:onClick="function" : function to call in activity when clicked(must be public, void, and take a View arg)

android:text="text" : text to put in the button

TextView

android:id="@+id/theID" : unique ID for use in Java code

android:text="string" : text to display

ScrollView

<ScrollView> 스크롤 뷰에 포함할 것들 </ScrollView>

Sizing and Positioning

과거 : Absolute positioning - 프로그래머가 정확한 픽셀이나 크기를 지정해놓음, 기기마다 화면이 다르므로 적절한 방법은 아니었음.

ViewGroup(위젯 또는 view를 포함함) as layout (XML로 표현)

ViewGroup superclass represents containers of views

- layouts are dexcribed in XML and mirrored in Java code

- Android provides several pre-existing layout managers; you can define your own custome layouts if needed.

- layouts can be nested to achieve combinations of features.

In the Java code and XML:

- an Activity is a ViewGroup

- various Layout classes are also ViewGroups

- widgets can be added to ViewGroup, which will then manage that widgets position/size behavior.

XML

a language for decribing hierarchical text data.

- uses tags that consist of elements and attributes. Tags can be nested.

- Some tags are opened and closed; others self-close.

Changing layouts

: go to the Text view for your layout XML file.

: change open/close tags to new layout type, ex- LinearyLayout

: now go back to Design view and add widgets.

LinearLayout 

: lays out widgets/views in a single line

: orientation of horizontal or vertical

: items do not wrap if they reach edge of screen!

Gravity

: alignment direction that widgets are pulled.

: top, bottom, center

Widget box model

: content - size of widget itself

: padding 

- artificial increase to widget size outside of content

- extra space inside widget

- set padding to adjust all sides; paddingTop, Bottom, Left, Right for one side

- usually set to specific values like 10dp (some widgets have a default value ~16dp)

: border - outside padding, a line around edge of widget

: margin - invisible separation from neighboring widgets