Fragments | Android Developers

 

android getting started with fragments

To create a fragment, extend the Fragment class, then override key lifecycle methods to insert your app logic, similar to the way you would with an Activity class. One difference when creating a Fragment is that you must use the onCreateView() callback to define the layout. Get started with Android fragments by William J. Francis In Software Engineer, in Mobility on March 14, , AM PST After purchasing and using a Sony Tablet S, William J. Francis is. Mar 01,  · In FlashCardPager, most of the work will be done by a Fragment in one of its lifecycle methods. This guide does not cover the basics of fragments – if you are not yet familiar with fragments in baqiushi.cfd, see Fragments to help you get started with fragments. Start an App Project Create a new Android project called FlashCardPager.


Get started with Android fragments - TechRepublic


As the name would suggest, fragments are not independent entities, but are tied to a single activity. In many ways, they have functionality similar to activities. You have a lot to do, so you might employ a few minions to run around and do your laundry and taxes in exchange for lodging and food, android getting started with fragments.

However, if you use them well, they can provide:. When the user selects a breed, the app displays information about it. This tutorial utilizes an Android RecyclerView. Use the Download Materials button at the top or bottom of this tutorial to download and extract the Starter Project. Check out the project El Dogo app.

The MainActivity will host all of your wee fragments and DogListFragment contains code to display a list of dog breeds content so that you can focus on fragments. Build and run the project. For instance, an event happens when the fragment becomes visible and active, or when the fragment becomes unused and is removed. You can also add code and behaviors to callbacks for these events as you would for an activity. In Android, when using fragments, there are two alternative fragment implementations you can use.

One type is the fragment that is provided by the platform version. A platform version corresponds to the version of Android that a user is running. For example, android getting started with fragments, a device running Android 6. The second type is a support library fragment. When you include a support library, it is added to your project in the same manner as any third-party library. Using the support library has two benefits when developing applications android getting started with fragments multiple versions of Android.

First, it ensures that you have consistency in your code and functionality across different devices and platform versions. This means that bugs and fixes will be more consistent across different versions of Android using these libraries.

Second, when they add new features to the latest version of Android, the Android team will often back-port these features via the support library in order for developers to use on older versions of Android.

Android has deprecated platform fragments in Android 9. So you should always go with the v4 support library when using fragments. Eventually, El Dogo will show a list of dogs breeds on launch and tapping on any of the items will display details about that particular breed.

This XML file lays out the dog detail display. It also displays one of the drawable resources and the associated String resources. Locate the DogDetailsFragment. This class will be responsible for displaying details for a selected breed. Activities use setContentView to specify the XML file that defines their layouts, but fragments create their view hierarchy in onCreateView.

Here you called LayoutInflater. The third parameter of inflate specifies whether the inflated fragment should be added to the container. You should always set this to false when inflating a view for a fragment: The FragmentManager will take care of adding the fragment to the container. Each activity has a FragmentManager that manages its fragments. It also provides an interface for you to access, android getting started with fragments, add and remove those fragments.

First, because you did not define any constructors, the compiler automatically generates an empty, default constructor that takes no arguments. This is all that you should have for a fragment: no other constructors. Second, you probably know that Android may destroy and later re-create an activity and all its associated fragments when the app goes into the background.

When the activity comes back, its Android getting started with fragments starts re-creating fragments by using the empty default constructor. If it cannot find one, you get an exception. For this reason, it is best practice to never specify any non-empty constructors. In fact, the easiest thing to do is to specify none as you did here. What if you need to pass information or data to a Fragment? This is also sometimes called Adding a Fragment Statically. By including this in the XML, android getting started with fragments, the FragmentManager knows to add this fragment to the activity automatically.

Embrace the Zen of deleting code! Open DogListFragment. You can see that the DogListFragment has no explicit constructors and a newInstance. The list code in DogListFragment depends on some resources. You have to ensure that the fragment has a valid reference to a Context for accessing those resources. The GridLayoutManager helps in positioning items in the breed list, android getting started with fragments.

The other import is for standard fragment overrides. Inside of DogListFragment. Because the code is in onAttachyou can rest assured that the fragment has a valid Context. Next open MainActivity. You ask your new friend, FragmentManagerto add it. When an activity saves, all of its active fragments are also saved. FragmentManager helped achieve this awesomeness through FragmentTransactionswhich are basically fragment operations such as add and remove. The problem with that is that if you change the value of name for programmeryou would need to do a subsequent setText to the TextView in order to update the item.

Imagine having a tool where you could bind a variable from your fragments and activities to your view and allow for changes to the variable to automatically update in the View. That is what data binding does for you. Your data class contains data that you want to use in your fragment and display in your view. The data field contains variables consisting of name and type options which specify the type and name of the variable being bound.

For example, the following would set a text field to the value held by the name field of the dogModel variable. You android getting started with fragments see this in the TextView with the ID name :. Now that you have your view set up, you need to access your view and bind the variables to it. This is where the data binding magic comes in! Whenever a android getting started with fragments has a data field, the framework automatically generates a binding object.

It creates the name of the object by converting the snake case name of the view into camel case and adding binding to the name. You can then inflate the view via the inflater method on the binding object and set properties via standard property access mechanisms.

MVVM consists of three components:. To start, open DogListFragment. This defines a listener interface for the activity to listen to the fragment. The activity will implement this interface and the fragment will invoke the onDogSelected when the user selects an item, passing the selection to the activity. In onAttachadd the following directly below super.

This initializes the listener reference. Wait until onAttach to ensure that the fragment android getting started with fragments attached itself. Then verify that the activity implements the OnDogSelected interface via is. If it does, set the activity as the listener for DogListFragment. This adds a View. OnClickListener to each dog breed so that it invokes the callback on the listener, the activity, to pass along the selection. Open MainActivity.

Add the following import below the existing imports so that you can use toasts:. The error is gone! Android getting started with fragments and run, android getting started with fragments. Once the app launches, click one of the dog breed. You should see a android getting started with fragments message naming the clicked item:. This is almost the same as the layout was before except with data binding added.

The text for name and description is bound to the variables of the same name in the DogModel object. A binding adapter allows you to perform actions on an element which are not supported by default data binding. In your case, you are storing a resource integer for the image to display, but data binding does not provide a default way to display an image from an ID. To fix that, you have a BindingAdapter that takes a reference to the object from which it was invoked, along with a parameter.

It uses that to call setImageResource on the imageView that displays the image of the dog. Now that your view is set up, replace newInstance in DogDetailsFragment with the code shown below:. A fragment can take initialization parameters through its arguments, android getting started with fragments, which you access via the arguments property.

The arguments are actually a Bundle that stores them as key-value pairs, like the Bundle in Activity. As you learned earlier, when a fragment is re-created, the default empty constructor is used— no parameters for you. Because the fragment can recall initial parameters from its persisted arguments, you can utilize them in the re-creation. The above code also stores information about the selected breed in the DogDetailsFragment arguments.

 

Android Fragments Tutorial: An Introduction with Kotlin | baqiushi.cf

 

android getting started with fragments

 

To create a fragment, extend the Fragment class, then override key lifecycle methods to insert your app logic, similar to the way you would with an Activity class. One difference when creating a Fragment is that you must use the onCreateView() callback to define the layout. Get started with Android fragments by William J. Francis In Software Engineer, in Mobility on March 14, , AM PST After purchasing and using a Sony Tablet S, William J. Francis is. Mar 01,  · In FlashCardPager, most of the work will be done by a Fragment in one of its lifecycle methods. This guide does not cover the basics of fragments – if you are not yet familiar with fragments in baqiushi.cfd, see Fragments to help you get started with fragments. Start an App Project Create a new Android project called FlashCardPager.