Basics of learning Android from 0 (3)-layout manager of view Components

Basics of learning Android from 0 (3)-layout manager of view Components
Android layout managerAndroid ActivityThe component binds the display interface for the activity through setContentView (xml resId, however, in order to better manage the various controls in the user interface of the Android Application (a series of components such as button text box editing and box image), Android provides us with a layout manager. By using the layout manager, the graphic interface of Android is unrelated to the java code, so that the code is separated from the layout, thus reducing the amount of code, the Code only requires some interface component control and some data processing, which is a bit similar to the MVC (modle view control) Structure in java. The layout manager in android plays the role of View, java code plays the role of control, and data storage in android plays the role of modle. After introducing what the layout manager is, next we will introduce the layout manager categories, including: LinearLayout relative layout (RelativeLayout) grid layout (GridLayout) frameLayout (AbsoluteLayout) describes the functions of various layout managers.LinearLayout)First, go to the official documentation to see the introduction of the official documentation (you must read the official documentation). The following official means: arrange its sub-layout in a single column or line. You can call setorientation () to set the direction of the row. You can also specify the arrangement mode. You can set LinearLayout. layoutparams to specify all the sub-elements in the arrangement. Call setgravity () or specify the child weight to fill the layout of the remaining space. The default direction is horizontal. Another important thing is that the components in LinearLayout are arranged in a direction that exceeds the screen width, and the more components are not displayed. Let's take a look at the XML attributes and related methods of LinearLayout, as shown in the following table: the official document will introduce the attributes of the official document in detail: This attribute is set to false, the layout manager is blocked from alignment with its child elements. This is especially useful when its sub-elements use different weights. The default value is true. It must be a Boolean value, which is true or false. When the vertical layout is set, the split between the two buttons sets the alignment of components in the layout manager, this attribute supports top, bottom, left, right, center_vertical, fill_vertical, numeric, fill_horizontal, center, fill, clip_vertical, and clip_horizontal attributes. You can also specify multiple combinations. For example: left | center_vertical indicates that it appears on the left of the screen and is vertically centered. When this attribute is set to true, all child elements with weight have the minimum size of the Maximum child element. You can set the arrangement of components in the layout manager to either horizontal or vertical, vertical by default; in the XML of LinearLayout, for example: android: weightSu M = "5" indicates that the LinearLayout is divided into five areas in total. Then, the controls in LinearLayout use android: layout_wetght = "1 ", this indicates it occupies 1/5 of the layout. After introducing the above LinearLayout attributes, we will use the following examples to demonstrate the use of these attributes: Through the above examples, you can just understand the effects of the attributes of LinearLayout. 2. The relative layout (RelativeLayout) introduces the method through the official Linearlayout document. You can go to the Android official website to view the method and follow the steps above to learn other components. The following layout managers will not be explained in the above way, but will be introduced to you in a brief and clear way. The position of the child components inside the relative layout container is always determined by the sibling component and parent container. Therefore, this layout method is called relative layout, for example: if the position of component B is determined by the position of component A, you must first define component B and determine the position of component B before defining component. Description of XML attributes and related methods of RelativeLayout

XML attributes	Java method	Description
Android: gravity	SetGravity (int)	Sets the alignment of child components in the layout container.
Android: ignoreGravity	SetIgnoreGravity (int)	Set which component does not accept gravity attribute impact

To control the distribution of child components in the layout container, Relative also provides an internal class: RelativeLayout. layoutParams, which provides a large number of XML attributes to control the layout distribution of child components in the Relative layout container. Its xml attributes are shown in the following table:

The values below can only be true or false.

Android: layout_centerHorizontal	Determines whether the child widget is horizontally centered in the layout container.
Android: layout_centerVertical	Determines whether the child widget is in the vertical center of the layout container.
Android: layout_centerInparent	Determines whether the child widget is located in the center of the layout container.
Android: layout_alignParentBottom	Determines whether the child widget is aligned at the bottom of the layout container.
Android: layout_alignParentLeft	Determines whether the child widget is aligned to the left of the layout container.
Android: layout_alignParentRight	Determines whether the child widget is aligned to the right of the layout container.
Android: layout_alignParentTop	Determines whether the child widget is aligned at the top of the layout container.

The following attribute values can only be the id values of other UI components.

Android: layout_toRightOf	Control the sub-component to the right of the id component
Android: layout_toLeftOf	Control the sub-component to the left of the id component
Android: layout_abve	Control the sub-component to be located above the id component given
Android: layout_below	Control the sub-component to be located below the given id component
Android: layout_alignTop	Controls the child widget to be located at the upper boundary alignment of the given id widget.
Android: layout_alignBottom	Controls the sub-component to be located at the bottom boundary alignment of the given id component.
Android: layout_alignLeft	Controls that the child widget is located at the left boundary alignment of the id widget.
Android: layout_alignRight	Controls that the child widget is located at the right boundary alignment of the id widget.

 

The following uses a snowflake effect to show the specific effect of Relative.

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3. Grid layout (GridLayout)  The grid layout is a new layout manager launched after Android4.0. As the name suggests, the grid layout divides the entire container into rows X columns grids, each of which has one component, in addition, you can set how many columns A component spans and how many lines a component spans. The xml attributes and related methods of gridlayout are as follows: 

Xml attributes	Related Methods	Description
Andorid: alignmentMode	SetAlignmentMode (int)	Sets the alignment mode used by the layout manager.
Android: columnCount	SetColumnCount (int)	Set the number of columns in the grid.
Android: columnOrderPreserved	SetColumnOrderPreserved (boolean)	Set whether the empty container of the grid retains column numbers.
Android: rowCount	SetRowCount (int)	Set the number of rows in the grid.
Android: rowOrderPreserved	SetRowOrderPreserved (boolean)	Set whether the Grid container retains row numbers.
Androi: useDefaultMargins	Setdefamarmargins (boolean)	Sets whether the layout manager uses the default margins.

To control the distribution of child components in the GridLayout layout container, GridLayout also provides an internal class: GridLayouut. params, which provides a large number of XML attributes to control the layout distribution of neutron components in the GridLayout layout container. XML Attribute of GridLayout. LayoutParams

Xml attributes	Related Methods	Description
Android: layout_column		Set the column number of the Child widget in GridLayout.
Android: layout_columSpan		Sets the number of columns that the child widget spans horizontally in GridLayout.
Android: layout_gravity	SetGravity (int)	Sets the method in which the sub-component occupies the space of the grid.
Android: layout_row		Set the row number of the Child widget in GridLayout.
Android: layout_rowSpan		Sets the number of lines that the child widget spans vertically in GridLayout.

The following uses a calculator as an example to describe how to use GridLayout:

4. frame layout creates a blank area for each component that is added to the frame layout (FramLayout). It is called a frame, and each sub-component occupies one frame, however, these components are automatically aligned according to the grivaty attribute. In fact, it can be understood as a heap of playing cards. One Card is stacked together, and the above card is placed on the following card. Common attributes and related methods of FrameLayout

Xml attributes	Related Methods	Description
Android: foreground	SetForeground (Drawable)	Set the foreground image of the frame layout container
Android: foregroundGravity	SetForegroundGravity (int)	Define the gravity attribute for creating foreground images

 <framelayout android:layout_height="match_parent" android:layout_width="match_parent" xmlns:android="http://schemas.android.com/apk/res/android">    
     
      
   
  
 </framelayout>

As follows: 5. Absolute layout (AbsoluteLayout)  Absolute layout: You can directly set the component's position by setting the X and Y coordinates of the component. However, the layout manager does not manage the position and size of the Child component, which is completely set by developers. However, it is not recommended to use absolute layout to control the size of sub-components, because the differences between mobile phones running Android on the market differ by, and their screen sizes and resolutions are quite different, with absolute layout, it is impossible to achieve the same effect on various screens. Therefore, the AbsoluteLayout manager is no longer suitable for use in projects.