Android View Hierarchy

A block of the screen which is responsible for the UI of the application is called a View. An android app UI consists of views and ViewGroups. View refers to android.view.View class of android, with the help of this class all the other GUI elements are drawn. It is responsible for drawing and event handling in android applications. Below are some common views available in Android.

TextView

TextView refers to the widget which displays some text on the screen based on the layout, size, color, etc set for that particular TextView. It optionally allows us to modify or edit itself as well.

Below is the XML code for it.

XML

<!--  XML code of textView -->
<TextView
  android:id="@+id/text_view_id"
  android:layout_height="wrap_content"
  android:layout_width="wrap_content"
  android:text="@string/hello" />

ImageView

ImageView class is used to display any kind of image resource in the android application either it can be android.graphics.Bitmap or android.graphics.drawable.Drawable (it is a general abstraction for anything that can be drawn in Android). ImageView class or android.widget.ImageView inherits the android.view.View class which is the subclass of Kotlin. AnyClass.Application of ImageView is also in applying tints to an image in order to reuse a drawable resource and create overlays on background images. Moreover, ImageView is also used to control the size and movement of an image.

Below is the XML code for it.

XML

<!--  XML code of ImageView -->
<ImageView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:src="@drawable/my_image"
  android:contentDescription="@string/my_image_description"/>

Button

In Android applications, a Button is a user interface that is used to perform some action when clicked or tapped. It is a very common widget in Android and developers often use it. 

Below is the XML code for it.

XML

<!-- XML code for Button -->
<Button
  android:id="@+id/button_id"
  android:layout_height="wrap_content"
  android:layout_width="wrap_content"
  android:text="@string/self_destruct" />

EditText

EditText is one of the basic UI widgets, which is used to take input from the user. The EditText is derived or is the extension of the TextView in Android. 

Below is the XML code for it.

XML

<!--  XML code of Edittext -->
<EditText
  android:id="@+id/plain_text_input"
  android:layout_height="wrap_content"
  android:layout_width="match_parent"
  android:inputType="text"/>

Syntax for a View

<ViewName
  Attribute1=Value1
  Attribute2=Value2
  Attribute3=Value3
  .
  .
  AttributeK=ValueK
/>

Views Example in Android

For more views visit this link.

View Hierarchy in Android

In this hierarchy, Views of Android are creating a Hierarchy of views and ViewGroups in the UI part of the android application. Basically nested Views make view hierarchy in android. The outer view becomes the parent of the inner view and the inner view is its child. It makes a tree-like structure. Below is a Hierarchy of views in Android for better understanding :