Android App Interface programming

Most Android UI components are placed in the Android.widget,android.view package and its sub-packages, so the UI components inherit the view class, and the view represents a blank rectangular area.

Android all UI components are built on the view and viewgroup basis; The view class is the base class for all UI components, and ViewGroup is an abstract class that usually uses its subclasses as a container;

View class

The view class is the base class for all visual controls, and mainly provides methods for control and event handling, such as Textview,button,checkbox.

View class Common Properties and corresponding method description:

Android:background

Setbackgroundresource (int)

Set background

Android:clickable

Setclickable (Boolean)

Sets whether view responds to click events

Android:visibility

setvisibiltiy (int)

Control the visibility of a view

Android:focusable

Setfocusable (Boolean)

Controls whether the view can get focus

Android:id

SetId (int)

To set the identifier for the view, you can get the ID by using the Findviewbyid method

Android:longclickable

Setlongclickable (Boolean)

Sets whether the view responds to long click events

Android:soundeffecteabled

Setsoundeffectsenable (Boolean)

Sets whether the view triggers the click and other events to play sound effects

Android:saveenable

Setsaveenabled (Boolean)

Whether the view freezes when the state is saved

Android:nextfocusdown

Setnextfocusdownid (int)

Defines the view that gets the focus down

Android:nextfocusleft

Android:nextfocusright

Android:nextfocusup

View that defines the focus for different operational directions

Any subclass that inherits view has properties and methods as above;

The ViewGroup class is a subclass of the view class, but can act as a container for other controls, and the ViewGroup child controls can be either normal view or viewgroup;

About the relationship between view and ViewGroup

View is a base class, ViewGroup is a subclass of view;

View represents a block of space that can be drawn by a user interface component;

Each view occupies a rectangular area on the screen, where the view is responsible for image rendering and event handling;

The view class is the parent of the Gizmo widgets and ViewGroup; ViewGroup is the base class of layout;

Linear layout

Provides a model for horizontal or vertical control of controls;

Android:orientation

setorientation (int) Sets the orientation of the linear layout;

Android:gravity

setgrabity (int) Sets the layout of elements within a linear layout;

Table layout

The Tablelayout class manages controls in the form of rows and classes, each of which behaves as a TableRow object, or a view object that spans all classes of that row when it is a view object;

In a table layout, the width of a column is specified by the widest cell in the column, and the width of the table is specified by the parent container;

In Tablelayout, you can set the following 3 properties for a column;

shrinkable If a column is marked as shrinkable, the width of the column can be shrunk so that the table adapts to the size of its parent container;

stretchable if a column is stretchable by the flag bit, the width of the column can be stretched to fill the free space in the table.

Collapsed, the column will be hidden;

Tablelyout inherits the LinearLayout class, and the properties and methods that are unique to the Tablelyout class are as follows:

Setcolumncollapsed (Int,boolean)

Column number starting with 0, setting the column number specified as collapsed

Similarly, shrinkable,stretchable can be set;

Relativelayout

In relative layout, the position of the child control is relative to the sibling control or the parent container;

Property name	Property Description
Android:layout_centerhorizontal	The current control is in the horizontal middle position of the parent control
Android:layout_centervertical	The current control is in the vertical middle position of the parent control
Android:layout_centerinparent	The current control is in the central location of the parent control
Android:layout_alignparentbottom	Aligns the bottom of the current control with the bottom of the parent control
Android:layout_alignparentleft	Aligns the left side of the current control with the left side of the parent control
Android:layout_alignparentright	Aligns the right side of the current control to the right side of the parent control
Android:layout_alignparenttop	Aligns the top of the current control with the top of the parent control
Android:layout_alignwithparentifmissing	Referencing a parent control when the reference control does not exist or is not visible

Next, look at the property values for the other control IDs, as shown in table 3-6.

Table 3-6 Properties and descriptions for values in relative layouts for other control IDs

Property name	Property Description
Android:layout_torightof	Causes the current control to be positioned to the right of the given ID control
Android:layout_toleftof	Causes the current control to be positioned to the left of the given ID control
Android:layout_above	Causes the current control to be positioned above the given ID control
Android:layout_below	Causes the current control to be located below the given ID control
Android:layout_aligntop	Aligns the top bounds of the current control with the top boundary of the given ID control
Android:layout_alignbottom	Aligns the bottom boundary of the current control with the bottom boundary of the given ID control
Android:layout_alignleft	Aligns the left bounds of the current control with the left edge of the given ID control
Android:layout_alignright	Aligns the right boundary of the current control with the right border of the given ID control

Finally, the attributes and descriptions of the attribute values in pixels are described, as shown in table 3-7.

Table 3-7 Properties and descriptions of pixels in relative layout

Property name	Property Description
Android:layout_marginleft	Leave white on the left side of the current control
Android:layout_marginright	Left white on the right side of the current control
Android:layout_margintop	White left over the current control
Android:layout_marginbottom	Leave white below the current control

Framelayout class

Frame layout

Framelayout frame layout Creates an area on the screen where multiple child controls can be added, but all child controls are aligned to the upper-left corner of the screen, and the size of the frame layout is determined by the largest child control in the control, if the child controls are the same size, Only the topmost child controls can be seen at the same time;

The properties and methods that framelayout inherit from Viewgroup,framelayout are as follows:

Android:foreground

Setforeground (drawable)

Set the content to draw on all child controls

Android:foregroundgravity

setforegroundgraviety (int)

Sets the gravity property that paints content on all child controls

In Framelayout, the child controls are drawn through the stack, so the added child controls are drawn on top;

Absolutelayout class

The so-called absolute layout, refers to all the controls placed on the screen control position is specified by coordinates;

Android App Interface programming