User Interface & Navigation | Android Developers

 

android ui elements list

Android Common UI elements All user interface elements in an Android app are built using View and ViewGroup objects. A View is an object that draws something on the screen that the user Author: Sandeep. Dec 20,  · Also, remember that in the world of android almost every brand and every carrier change things a little bit to make it "better". This means that many UI elements may look different or have different colors in many devices. Also remember that different android versions (, , , ) also have some differences. Android ListView is a view which groups several items and display them in vertical scrollable list. The list items are automatically inserted to the list using an Adapter that pulls content from a source such as an array or database.. List View. An adapter actually bridges between UI components and the data source that fill data into UI Component.


user interface - Is there a graphical overview of all Android GUI element? - Stack Overflow


A layout defines the structure for a user interface in your app, such as in an activity. All elements in the layout are built using a hierarchy of View and ViewGroup objects. A View usually draws something the user can see and interact with. Whereas a ViewGroup is an invisible container that defines the layout structure for Android ui elements list and other ViewGroup objects, as shown in figure 1. Figure 1. Illustration of a view hierarchy, which defines a UI layout.

The View objects are usually called "widgets" and can be one of many subclasses, such as Button or TextView, android ui elements list. The ViewGroup objects are usually called "layouts" can be one of many types that provide a different layout structure, such as LinearLayout or ConstraintLayout, android ui elements list. Declaring your UI in XML allows you to separate the presentation of your app from the code that controls its behavior.

Using XML files also makes it easy to provide different layouts for different screen sizes and orientations discussed further in Supporting Different Screen Sizes. The Android framework gives you the flexibility to use either or both of these methods to build your app's UI, android ui elements list. For example, you can declare your app's default layouts in XML, android ui elements list, and then modify the layout at runtime.

Tip: To debug your layout at runtime, use the Layout Inspector tool. Each layout file must contain exactly one root element, which must be a View or ViewGroup object. Once you've defined the root element, you can add additional layout objects or widgets as child elements to gradually build a View hierarchy that defines your layout. After you've declared your layout in XML, save the file with the. More information about the syntax for a layout XML file is available in the Layout Resources document.

When you compile your app, each XML layout file is compiled into a View resource. You should load the layout resource from your app code, in your Activity. Do so by calling setContentViewpassing it the reference to your layout resource in the form of: R. The onCreate callback method in your Activity is called by the Android framework when your Activity is launched see android ui elements list discussion android ui elements list lifecycles, in the Activities document.

Some attributes are specific to a View object for example, android ui elements list, TextView supports the textSize attributebut these attributes are also inherited by any View objects that may extend this class. Some are common to all View objects, because they are inherited from the root View class like the id attribute.

And, other attributes are considered "layout parameters," which are attributes that describe certain layout orientations of the View object, as defined by that object's parent ViewGroup object, android ui elements list.

Any View object may have an integer ID associated with it, to uniquely identify the View within the tree. When the app is compiled, this ID is referenced as an integer, but the ID is typically assigned in the layout XML file as a string, in the id attribute.

This is an XML attribute common to all View objects defined by the View class and you will use it very often. The at-symbol at the beginning of the string indicates that the XML parser should parse and expand the rest of the ID string and identify it as an ID resource. There are a number of other ID resources that are offered by the Android framework. When referencing an Android resource ID, you do not need the plus-symbol, but must add the android package namespace, like so:.

With the android package namespace in place, android ui elements list, we're now referencing an ID from the android. R resources class, rather than the local resources class. Defining IDs for view objects is important when creating a RelativeLayout. In a relative layout, sibling views can define their layout relative to another sibling view, which is referenced by the unique ID. An ID need not be unique throughout the entire tree, but it should be unique within the part of the tree you are searching android ui elements list may often be the entire tree, so it's best to be completely unique when possible.

Every ViewGroup class implements a nested class that extends ViewGroup, android ui elements list. This subclass contains property types that define the size and position for each child view, as appropriate android ui elements list the view group, android ui elements list.

As you can see in figure 2, android ui elements list, the parent view group defines layout parameters for each child android ui elements list including the child view group. Figure 2. Visualization of a view hierarchy with layout parameters associated with each view. Note that every LayoutParams subclass has its own syntax for setting values.

Each child element must define LayoutParams that are appropriate for its parent, though it may also define different LayoutParams for its own children. Many LayoutParams also include optional margins and borders. You can specify width and height with exact measurements, though you probably won't want to do this often.

More often, you will use one of these constants to set the width or android ui elements list. In general, specifying a layout width and height using absolute units such as pixels is not recommended. The accepted measurement types are defined in the Available Resources document. The geometry of a view is that of a rectangle.

A view has a location, expressed as a pair of left and top coordinates, and two dimensions, expressed as a width and a height. The unit for location and dimensions is the pixel. It is possible to retrieve the location of a view by invoking the methods getLeft and getTop.

The former returns the left, or X, coordinate of the rectangle representing the view. The latter returns the top, or Y, coordinate of the rectangle representing the view. These android ui elements list both return the location of the view relative to its parent. For instance, when getLeft returns 20, that means the view is located 20 pixels to the right of android ui elements list left edge of its direct parent. In addition, several convenience methods are offered to avoid unnecessary computations, namely getRight and getBottom.

These methods return the coordinates of the right and bottom edges of the rectangle representing the view. The size of a view is expressed with a width and a height.

A view actually possesses two pairs of width and height values. The first pair is known as measured width and measured height. These dimensions define how big a view wants to be within its parent. The measured dimensions can be obtained by calling getMeasuredWidth and getMeasuredHeight. The second pair is simply known as width and heightor sometimes drawing width and drawing height.

These dimensions define the actual size of the view on screen, at drawing time and after layout. These values may, but do not have to, android ui elements list, be different from the measured width and height. The width and height can be obtained by calling getWidth and getHeight.

To measure its dimensions, a view takes into account its padding. The padding is expressed in pixels for the left, top, right and bottom parts of the view. Padding can be used to offset the content of the view by a specific number of pixels. For instance, a left padding of 2 will push the view's content by 2 pixels to the right android ui elements list the left edge.

Even though a view can define a padding, it does not provide any support for margins. However, view groups provide such a support. Refer to ViewGroup and ViewGroup. MarginLayoutParams for further information, android ui elements list. For more information about dimensions, see Dimension Values. Each subclass of the ViewGroup class provides a unique way to display the views you nest within it, android ui elements list.

Below are some of the more common layout types that are built into the Android platform. Note: Although you can nest one or more layouts within another layout to achieve your UI design, you should strive to keep your layout hierarchy as shallow as possible. Your layout draws faster if it has fewer nested layouts a wide view hierarchy is better than a deep view hierarchy.

A layout that organizes its children into a single horizontal or vertical row. It creates a scrollbar if the length of the window exceeds the length of the screen. Enables you to specify the location of child objects relative to each other child A to the left of child B or to the parent aligned to the top of the parent, android ui elements list. When the content for your layout is dynamic or not pre-determined, you can use a layout that subclasses AdapterView to populate the layout with views at runtime.

A subclass of the AdapterView class uses an Adapter to bind data to its layout. The Adapter behaves as a middleman between the data source and the AdapterView layout—the Adapter retrieves the data from a source such as an array or a database query and converts each entry into a view that can be added into the AdapterView layout.

You can populate an AdapterView such as ListView or GridView by binding the AdapterView instance to an Adapterandroid ui elements list, which retrieves data from an external source and creates a View that represents each data entry. Android provides several subclasses of Adapter that are useful for retrieving different kinds of data and building views for an AdapterView.

The two most common adapters are:. For example, if you have an array of strings you want to display in a ListViewinitialize a new ArrayAdapter using a constructor to specify the layout for each string and the string array:. Then simply call setAdapter on your ListView :. To customize the appearance of each item you can override the toString method for the objects in your array.

Or, to create a view for each item that's something other than a TextView for example, if you want an ImageView for each array itemextend the ArrayAdapter class and override getView to return android ui elements list type of view you want for each item. When you instantiate the SimpleCursorAdapterpass the layout to use for each result, the Cursor containing the results, and these two arrays:. The SimpleCursorAdapter then creates a view for each row in the Cursor using the provided layout by inserting each fromColumns item into the corresponding toViews view.

If, during the course of your app's life, you change the underlying data that is read by your adapter, you should call notifyDataSetChanged. This will notify the attached view that the data has been changed and it should refresh itself. You can respond to click events on each item in an AdapterView by implementing the AdapterView. OnItemClickListener interface.

For example:.

 

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android ui elements list

 

Dec 20,  · Also, remember that in the world of android almost every brand and every carrier change things a little bit to make it "better". This means that many UI elements may look different or have different colors in many devices. Also remember that different android versions (, , , ) also have some differences. Android provides a wide variety of controls you can use in your UI, such as buttons, text fields, seek bars, check box, zoom buttons, toggle buttons, and many more. UI Elements A View is an object that draws something on the screen that the user can interact with and a ViewGroup is an object that holds other View (and ViewGroup) objects in order to define the layout of the user interface. Declare UI elements in XML. Android provides a straightforward XML vocabulary that corresponds to the View classes and subclasses, such as those for widgets and layouts. You can also use Android Studio's Layout Editor to build your XML layout using a drag-and-drop interface. Instantiate layout elements at runtime. Your app can create View and ViewGroup objects (and manipulate their properties) .