Android views and view groups

Difference Between View and ViewGroup in Android

In Android Layout is used to describe the user interface for an app or activity, and it stores the UI elements that will be visible to the user. An android app’s user interface is made up of a series of View and ViewGroup elements. In most cases, android apps will have one or more operations, each of which is a single screen of the app. Multiple UI components will be present in the operations, and those UI components will be instances of the View and ViewGroup subclasses. Generally, the android apps will contain one or more activities and each activity is one screen of the app. The activities will contain multiple UI components and those UI components are the instances of View and ViewGroup subclasses. In Android apps, the two very central classes are the Android View class and ViewGroup class. One or more tasks can be found in an Android app. A screen in an Android operation is identical to the windows in a desktop application. GUI components may be used in an operation. View or ViewGroup subclasses are used to build the GUI elements.

View is a basic building block of UI (User Interface) in android. A view is a small rectangular box that responds to user inputs. Eg: EditText, Button, CheckBox, etc. ViewGroup is an invisible container of other views (child views) and other ViewGroup. Eg: LinearLayout is a ViewGroup that can contain other views in it. ViewGroup is a special kind of view that is extended from View as its base class. ViewGroup is the base class for layouts. As the name states View is singular and the group of Views is the ViewGroup. In simple terms, a view is a user interface feature that we interact with when we use an app, such as a button, editing text and images, and so on. Android.view has a child class called View. Observe While the View group is the container that houses all of these views as well as many other ViewGroup such as linear or Frame Layout. For example, if we design and use the LinearLayout as the root feature, our main layout would be the LinearLayout. Within it, we can add another view category (i.e. another LinearLayout) and several other views such as buttons or TextViews.

View

The View class is the base class or we can say that it is the superclass for all the GUI components in android. For example, the EditText class is used to accept the input from users in android apps, which is a subclass of View, and another example of the TextView class which is used to display text labels in Android apps is also a subclass of View.

Or the other definition,

View refer to the android.view.View class, which is the base class of all UI classes. android.view.View class is the root of the UI class hierarchy. So from an object point of view, all UI objects are View objects. Following are some of the common View subclasses that will be used in android applications.

• TextView
• EditText
• ImageView
• RadioButton
• Button
• ImageButton
• CheckBox
• DatePicker
• Spinner
• ProgressBar and etc.

These are some of the view subclass available in android.

ViewGroup

The ViewGroup class is a subclass of the View class. And also it will act as a base class for layouts and layouts parameters. The ViewGroup will provide an invisible container to hold other Views or ViewGroups and to define the layout properties. For example, Linear Layout is the ViewGroup that contains UI controls like Button, TextView, etc., and other layouts also. ViewGroup Refer to the android.view.ViewGroup class, which is the base class of some special UI classes that can contain other View objects as children. Since ViewGroup objects are also View objects, multiple ViewGroup objects and View objects can be organized into an object tree to build a complex UI structure. Following are the commonly used ViewGroup subclasses used in android applications.

• FrameLayout
• WebView
• ListView
• GridView
• LinearLayout
• RelativeLayout
• TableLayout and many more.

The ViewGroup subclasses listed above group View instances together and takes care of their layout. For instance, the LinearLayout will render the components after each other either horizontally or vertically.

Difference Table

View	ViewGroup
View is a simple rectangle box that responds to the user’s actions.	ViewGroup is the invisible container. It holds View and ViewGroup
View is the SuperClass of All component like TextView, EditText, ListView, etc	ViewGroup is a collection of Views(TextView, EditText, ListView, etc..), somewhat like a container.
A View object is a component of the user interface (UI) like a button or a text box, and it’s also called a widget.	A ViewGroup object is a layout, that is, a container of other ViewGroup objects (layouts) and View objects (widgets)
Examples are EditText, Button, CheckBox, etc.	For example, LinearLayout is the ViewGroup that contains Button(View), and other Layouts also.
View refers to the android.view.View class	ViewGroup refers to the android.view.ViewGroup class
android.view.View which is the base class of all UI classes.	ViewGroup is the base class for Layouts.

So, these all are the basic key difference between the View class and Viewgroup class in Android.

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Android From Scratch: Understanding Views And View Groups

Aside from a handful of edge cases, every application that you build has some form of user interface. On Android, this is accomplished through the use of View and ViewGroup objects. In this article, you learn about some of the more commonly used View components available for displaying content and you are introduced to how they are used.

Do you find it easier to learn with video? Why not check out our course:

1. Views

View objects are used specifically for drawing content onto the screen of an Android device. While you can instantiate a View in your Java code, the easiest way to use them is through an XML layout file. An example of this can be seen when you create an simple «Hello World» application in Android Studio. The layout file is the one named activity_main.xml, looking something like this.

The above example shows a type of View that will be displayed on the screen. The layout_width and layout_height attributes state that View should only take up as much room on the screen as needed to display the text «Hello World!». The id attribute is how that View can be referenced in your Java code like this:

While you can set attributes for a View in XML, you can also change attributes in your Java code, such as changing the text of the above TextView .

The above code updates the text of the TextView to «This is a changed View». This is what that looks like when you run the app.

Now that you know how to work with basic View objects, let’s go over some of the different types that are available to you in the Android SDK.

Display Views

TextView

This is the View we used in the above example. The main job of the TextView is to display text on the screen of an Android app. While this may seem like a simple task, the TextView class contains complex logic that allows it to display marked up text, hyperlinks, phone numbers, emails, and other useful functionality.

ImageView

As the name implies, the ImageView is designed specifically to display images on the screen. This can be used for displaying resources stored in the app or for displaying images that are downloaded from the internet.

Input and Controls

Some View objects are used for more than just displaying content to users. Sometimes you need to receive some sort of input to control your applications. Luckily, Android provides several View subclasses specifically for this purpose.

Button

The Button class is one of the most basic controls available in an app. It listens for clicks from the user and calls a method in your code so that you can respond appropriately.

Switch and CheckBox

The Switch and CheckBox classes have an active and inactive state that can be toggled between. This is useful for changing settings in an app. Compatible versions with Material Design are available through the AppCompat support library.

EditText

This View subclass is an extension of the TextView class and allows users to update the contained text via a keyboard input.

Adapter Based Views

While each of the above View examples are single items, sometimes you want to display a collection of items. These View classes require the use of an Adapter to handle displaying the proper user interface per item in a collection.

ListView

The ListView class is used for displaying a collection of items in a linear, single-column, scrollable View . Each individual item can be selected for displaying more details or performing an action related to that item.

Similar to the ListView class, the GridView class takes an Adapter and displays items in multiple columns on the screen.

The final collection View class you learn about in this tutorial is the Spinner class. It accepts an Adapter and displays items in a dropdown menu when the Spinner is clicked so that an item can be selected by the user.

2. View Groups

A ViewGroup is an invisible object used to contain other View and ViewGroup objects in order to organize and control the layout of a screen. ViewGroup objects are used for creating a hierarchy of View objects (see below) so that you can create more complex layouts. That said, the more simple you can keep a layout, the more performant it is.

ViewGroup objects can be instantiated in the same way as standard View items in XML or in Java code.

While all ViewGroup classes perform a similar task, each ViewGroup subclass exists for a specific purpose. Let’s take a look at some of them.

The LinearLayout exists to display items in a stacked order, either horizontally or vertically. Linear layouts can also be used to assign weights to child View items so that the items are spaced on the screen in a ratio to each other.

This ViewGroup subclass allows you to display items on the screen relative to each other, providing more flexibility and freedom over how your layout appears compared to the LinearLayout .

Designed for displaying a single child View at a time, the FrameLayout draws items in a stack and provides a simple way to display an item across various screen sizes.

An extension of the FrameLayout , the ScrollView class handles scrolling its child objects on the screen.

Used for managing multiple views while only displaying one at a time, the ViewPager class accepts an Adapter and allows users to swipe left and right in order to see all available View items.

The RecyclerView class is a ViewGroup subclass that is related to the ListView and GridView classes and that has been made available by Google through the RecyclerView support library for older versions of Android. The RecyclerView class requires the use of the view holder design pattern for efficient item recycling and it supports the use of a LayoutManager , a decorator, and an item animator in order to make this component incredibly flexible at the cost of simplicity.

Recently added to the design support library, the CoordinatorLayout class uses a Behavior object to determine how child View items should be laid out and moved as the user interacts with your app.

3. Custom Views

While there is a wide variety of View and ViewGroup classes for you to use within your apps, you sometimes want to create something new to fit your needs. In this case, you can create a new Java class that extends either View or ViewGroup , depending on what you need. The act of creating a new custom View subclass is beyond the scope of this article, but you can find more information in this Envato Tuts+ tutorial.

Conclusion

In this tutorial, you have learned about one of the most basic components of Android, layouts and views. Given how fundamental these components are to Android, you will continuously learn new things about them as you continue to work with the Android platform and you will find new ways to do amazing things using them in your projects.

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Android View and ViewGroup with Examples

In android, Layout is used to define the user interface for an app or activity and it will hold the UI elements that will appear to the user.

The user interface in an android app is made with a collection of View and ViewGroup objects. Generally, the android apps will contain one or more activities and each activity is a one screen of app. The activities will contain a multiple UI components and those UI components are the instances of View and ViewGroup subclasses.

The user interface in an android app is made with a collection of View and ViewGroup objects. Generally, the android apps will contain one or more activities and each activity is a one screen of the app. The activities will contain multiple UI components and those UI components are the instances of View and ViewGroup subclasses.

Android View

The View is a base class for all UI components in android. For example, the EditText class is used to accept the input from users in android apps, which is a subclass of View .

Following are the some of common View subclasses that will be used in android applications.

Like these we have many View subclasses available in android.

Android ViewGroup

The ViewGroup is a subclass of View and it will act as a base class for layouts and layouts parameters. The ViewGroup will provide an invisible containers to hold other Views or ViewGroups and to define the layout properties.

For example, Linear Layout is the ViewGroup that contains a UI controls like button, textview, etc. and other layouts also.

Following are the commonly used ViewGroup subclasses in android applications.

Both View and ViewGroup subclasses together will play a key role to create a layouts in android applications.

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