INTRODUCTION AND BASICS OF Android NOTES.pptx
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ANDROID NOTES
INTRODUCTION AND BASICS OF Android NOTES.pptx
- 1. Android Layout is used to define the user interface that holds the UI controls or widgets that will appear on the screen of an android application or activity screen. Layouts in Android are used to define the way we want a screen to be shown. The Layout is the master plan or a blueprint of the printed/published work that lays out the order of its various graphic elements. Generally, every application is a combination of View and ViewGroup. As we know, an android application contains a large number of activities and we can say each activity is one page of the application. So, each activity contains multiple user interface components and those components are the instances of the View and ViewGroup. All the elements in a layout are built using a hierarchy of View and ViewGroup objects.
- 2. Views A `View` is the fundamental building block of any Android UI. It represents interactive elements like buttons, text fields, and images, serving as the user interface’s backbone. ViewGroups On the other hand, a `ViewGroup` is a specialized `View` that acts as a container for other views or view groups. It plays a pivotal role in organizing and arranging the layout of its child views.
- 3. Types of Android Layout Android Linear Layout: LinearLayout is a ViewGroup subclass, used to provide child View elements one by one either in a particular direction either horizontally or vertically based on the orientation property. Android Relative Layout: RelativeLayout is a ViewGroup subclass, used to specify the position of child View elements relative to each other like (A to the right of B) or relative to the parent (fix to the top of the parent). Android Constraint Layout: ConstraintLayout is a ViewGroup subclass, used to specify the position of layout constraints for every child View relative to other views present. A ConstraintLayout is similar to a RelativeLayout, but having more power. Android Frame Layout: FrameLayout is a ViewGroup subclass, used to specify the position of View elements it contains on the top of each other to display only a single View inside the FrameLayout.
- 4. Android Table Layout: TableLayout is a ViewGroup subclass, used to display the child View elements in rows and columns. Android Web View: WebView is a browser that is used to display the web pages in our activity layout. Android ListView: ListView is a ViewGroup, used to display scrollable lists of items in a single column. Android Grid View: GridView is a ViewGroup that is used to display a scrollable list of items in a grid view of rows and columns.
- 5. Different Attribute of the Layouts XML attributes Description android:id Used to specify the id of the view. android:layout_width Used to declare the width of View and ViewGroup elements in the layout. android:layout_height Used to declare the height of View and ViewGroup elements in the layout. android:layout_marginL eft Used to declare the extra space used on the left side of View and ViewGroup elements. android:layout_marginR ight Used to declare the extra space used on the right side of View and ViewGroup elements. android:layout_marginT op Used to declare the extra space used in the top side of View and ViewGroup elements. android:layout_marginB ottom Used to declare the extra space used in the bottom side of View and ViewGroup elements. android:layout_gravity Used to define how child Views are positioned in the layout.
- 6. LinearLayout is the most basic layout in android studio, that aligns all the children sequentially either in a horizontal manner or a vertical manner by specifying the android:orientation attribute. If one applies android:orientation=”vertical” then elements will be arranged one after another in a vertical manner and If you apply android:orientation=”horizontal” then elements will be arranged one after another in a horizontal manner. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity"> </LinearLayout>
- 7. LinearLayout- A LinearLayout aligns each of the child View in either a vertical or a horizontal line. A vertical layout has a column of Views, whereas in a horizontal layout there is a row of Views. It supports a weight attribute for each child View that can control the relative size of each child View within the available space.
- 8. Attributes Description android:layout_weight It is defined individually to the child’s views to specify how LinearLayout divides the remaining space amongst the views it contains android:weightSum Defines the total weight sum android:orientation How the elements should be arranged in the layout. It can be horizontal or vertical. android:gravity It specifies how an object should position its content on its X and Y axes. Possible values are – center_vertical, fill, center, bottom, end, etc. android:layout_gravity Sets the gravity of the View or Layout relative to its parent. Possible values are – center_vertical, fill, center, bottom, end, etc. android:baselineAligned This must be a boolean value, either “true” or “false” and prevents the layout from aligning its children’s baselines. android:id This gives a unique id to the layout.
- 9. How to arrange children views in a vertical manner <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity"> <!-- Add vertical in the android:orientation--> <!-- Add Button--> <Button android:layout_width="match_parent" android:layout_margin="10dp" android:layout_height="wrap_content"/>
- 10. <!-- Add Button--> <Button android:layout_width="match_parent" android:layout_margin="10dp" android:layout_height="wrap_content"/> <!-- Add Button--> <Button android:layout_width="match_parent" android:layout_margin="10dp" android:layout_height="wrap_content"/> </LinearLayout>
- 11. How to arrange children views in a horizontal manner <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" tools:context=".MainActivity"> <!-- Add horizontal in the android:orientation--> <!-- Add Button--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" />
- 12. <!-- Add Button--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" /> <!-- Add Button--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" /> </LinearLayout>
- 13. How to use layout_weight and weightSum <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" android:weightSum="3" tools:context=".MainActivity"> <!-- Add value in the android:weightSum--> <!-- Add horizontal in the android:orientation--> <!-- Add Button--> <!-- Add value in the android:layout_weight--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" android:layout_weight="1" />
- 14. <!-- Add Button--> <!-- Add value in the android:layout_weight--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" android:layout_weight="1" /> <!-- Add Button--> <!-- Add value in the android:layout_weight--> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" android:layout_weight="1" /> </LinearLayout>
- 15. 4. How to use gravity <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" android:weightSum="3" tools:context=".MainActivity"> <!-- Add value in the android:weightSum--> <!-- Add horizontal in the android:orientation--> <!-- Add Button--> <!-- Add value in the android:gravity --> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp"
- 16. android:layout_weight="1" android:gravity="bottom|center" android:text="GFG" /> <!-- Add Button--> <!-- Add value in the android:gravity --> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" android:layout_weight="1" android:gravity="center" android:text="GFG" /> <!-- Add Button--> <!-- Add value in the android:gravity --> <Button android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_margin="10dp" android:layout_weight="1" android:gravity="center|top" android:text="GFG" /> </LinearLayout>
- 17. How to use layout_gravity <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity"> <!-- Add vertical in the android:orientation--> <!-- Add Button--> <!-- Add value in the layout_gravity -->
- 18. <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_margin="10dp" /> <!-- Add Button--> <!-- Add value in the layout_gravity --> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="right" android:layout_margin="10dp" /> <!-- Add Button--> <!-- Add value in the layout_gravity --> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="left" android:layout_margin="10dp" /> </LinearLayout>