In Android, the user interface is defined in a layout. A layout can be declared in XML or created dynamically in code. (It's recommended to declare the layout in XML rather than in code to keep the presentation layer separate from the implementation layer.) A layout can define an individual ListItem, a fragment, or even the entire activity. Layout files are stored in the /res/layout folder and referenced in code with the following identifier: R.layout.<filename_without_extension>.

Android provides a useful variety of Layout classes that contain and organize individual elements of an activity (such as buttons, checkboxes, and other Views). The ViewGroup object is a container object that serves as the base class for Android's family of Layout classes. The Views placed in a layout form a hierarchy, with the topmost layout being the parent.

Android...

When using the Android Studio wizard to create a new project, it automatically creates the res/layout/activity_main.xml file (as shown in the following screenshot). It then inflates the XML file in the onCreate() callback with setContentView(R.layout.activity_main):

For this recipe, we will create two slightly different layouts and switch between them with a button.

Create a new project in Android Studio and call it InflateLayout. Once the project is created, expand the res/layout folder so we can edit the activity_main.xml file. Use the default Phone & Tablet settings on the Target Android devices and select Empty Activity on the Add...

As mentioned in the Introduction section, RelativeLayout allows Views to be position-relative to each other and the parent. RelativeLayout is particularly useful for reducing the number of nested layouts, which is very important for reducing memory and processing requirements.

Create a new project and call it RelativeLayout. Android Studio defaults to using a ConstraintLayout , which we will replace with a RelativeLayout for this example. Use the default Phone & Tablet settings on the Target Android devices and select Empty Activity on the Add an Activity to Mobile dialog.

Another common layout option is LinearLayout, which arranges the child Views in a single column or single row, depending on the orientation specified. The default orientation (if not specified) is vertical, which aligns the Views in a single column.

LinearLayout has a key feature not offered in RelativeLayout—the weight attribute. We can specify a layout_weight parameter when defining a View to allow the View to dynamically size based on the available space. Options include having a View fill all the remaining space (if a View has a higher weight), having multiple Views fit within the given space (if all have the same weight), or spacing the Views proportionally by their weight.

We will create LinearLayout with three EditText Views to demonstrate how the weight attribute can be used. For this example, we will use three EditText Views-one to enter...

When you need to create a table in your UI, Android provides two convenient layout options: TableLayout (along with TableRow) and GridLayout (added in API 14). Both layout options can create similar-looking tables, but each using a different approach. With TableLayout, rows and columns are added dynamically as you build the table. With GridLayout, row and column sizes are defined in the layout definition.

Neither layout is better, it's just a matter of using the best layout for your needs. We'll create a 3 x 3 grid using each layout to give a comparison, as you could easily find yourself using both layouts, even within the same application.

To stay...

As the name implies, ListView is designed for displaying lists of information.  If you have prior experience on Android, you’ve probably come across the ListView and possibly GridView controls before. If not while coding, most likely you’ve used it as an app, as it’s one of the most commonly used controls available. For most applications and users, the old ListView was probably sufficient and didn’t pose any problems. As an example, most users could probably see their list of emails in their inbox without any problems.  But for some, they might have so many emails in their inbox that when scrolling through their list, their device would stutter (slight pauses when scrolling). Unfortunately, ListView has many such performance problems.

The most significant performance issue with ListView is caused by creating...

In Android development, it's generally the preferred practice to define the UI with XML and the application code in Java, keeping the user interface code separate from the application code. There are times where it is much easier or more efficient, to alter (or even build) the UI from the Java code. Fortunately, this is easily supported in Android.

In this recipe, we will obtain a reference to the LayoutParams object to change the margin during runtime.

Here, we will set up a simple layout with XML and use a LinearLayout.LayoutParams object to change the margins of a View during runtime.  Create a new project using with an Empty Activity called RuntimeProperties...