Archivado en 10 junio 2019

Creating and Using Fragments CodePath Android Cliffnotes

10 junio, 2019

A fragment is always rooted in an activity and the fragment lifecycle is subject to the host activity’s lifecycle. In this step we open MainActivity and add the code for initiate the Button. After that we perform setOnClickListener on Button so whenever a user click on Button a message is displayed on the screen with the help of Toast.

  • After tapping a radio button, change the orientation of your device or emulator from portrait to landscape.
  • Although activities and fragments may look similar and interchangeable at first, in reality, they are very different.
  • The first argument passed to add() is the layout resource for the ViewGroup in which the Fragment should be placed.
  • FragmentManager – the class for interacting with a fragment inside of an activity.
  • Select the hardcoded text warning, click the Fix button and assign the string to a resource named change_text.

The second fragment will consist solely of a TextView object, also contained within a RelativeLayout view. Prior to fragment introduction, we had a limitation because we can show only a single activity on the screen at one given point in time. So we were not able to divide device screen and control different parts separately. But with the introduction of fragment we got more flexibility and removed the limitation of having a single activity on the screen at a time.


For example, using the same list across different data sources within an app. While performing Fragment Transaction we can add a Fragment into back stack that’s managed by the Activity. Back stack allow us to reverse a Fragment transaction on pressing Back button of device. For Example if we replace a Fragment and add it in back stack then on pressing the Back button on device it display the previous Fragment. 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. For the layout file, specify the type of layout, followed by the name of the layout, using a snake case syntax.

These functions include onCreate, onStart, onResume, onPause, onStop, and onDestroy. The callback methods are called depending on the fragment’s state. However, before creating this transaction, the code checks to see if the Fragment is displayed . If the Fragment is not displayed, there’s nothing to remove. In addition to the add() transaction, the code calls addToBackStack in order to add the transaction to a back stack of Fragment transactions. It allows the user to return to the previous Fragment state by pressing the Back button.

android studio fragment

I am easily able to see how the basics work and now I can implement this into my application. In this step we show the Android Manifest file in which do nothing because we need only one Activitty i.e MainActivity which is already defined in it. In our project we create two Fragment’s but we don’t need to define the Fragment’s in manifest because Fragment is a part of an Activity.

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The navigation controller allows us to access all the fragments and relationships defined in the navigation.xml file. The modification above allows us to access the views we declared in the fragment_question.xml file. We are focusing on the two buttons since they will help navigate to the other fragments. The Fragment class uses callback methods that are similar to Activity callback methods. For example, onCreateView() provides a LayoutInflater to inflate the Fragment UI from the layout resource fragment_simple. It will often be the case that we will want to know what is happening inside a fragment being displayed by an activity.

To proceed select «New Blank Fragment.» You will see a screen like the one below prompting you to generate a layout XML as well as some basic factory methods and callbacks. Since this application is intended to work on earlier versions of Android, it will also be necessary to make use of the appropriate Android support library. To properly manage the lifecycle of our fragment we need the third parameter for the inflater to be false. We don’t want the view automatically attached to the root container, we want the FragmentTransaction in Main Activity to take care of attaching the fragment. Before the introduction of fragments we could only show one Activity on the screen at time.

android studio fragment

You can combine multiple fragments in a single activity to build a multi-pane UI. You cannot replace a fragment defined statically in the layout file via a FragmentTransaction. You can only replace fragments that you added dynamically. A fragment is a reusable class implementing a portion of an activity. Fragments must be embedded in activities; they cannot run independently of activities. By using Fragments we can comprise multiple Fragments in a single Activity.

Implementation of the OnSeekBarChangeListener interface requires that the onProgressChanged(), onStartTrackingTouch() and onStopTrackingTouch() methods be implemented. Also declared is a variable in which to store a reference to the EditText object. The application created in this chapter will consist of a single activity and two fragments. The user interface for the first fragment will contain a toolbar of sorts consisting of an EditText view, a SeekBar and a Button, all contained within a RelativeLayout view.


And if the button 2 is selected, we will just call FragmentTwo class. To correctly create and set up an Activity, you need to create a new Kotlin class, which extends the AppCompactActivity class. Instead, the activity can be considered Digital Health: The Art of UX Design for Patient-Facing Health Apps Expert Interview like the container under which all other UI components will be placed. ( //the fragment is initialized and bound to the nav host activity. Similarly, draw an arrow from the correctFragment and wrongFragment to the questionFragment.

android studio fragment

We can combine multiple Fragments in Single Activity to build a multi panel UI and reuse a Fragment in multiple Activities. We always need to embed Fragment in an activity and the fragment lifecycle is directly affected by the host activity’s lifecycle. Now our program is running, you will see default this fragment 1 is selected here.

3 Edit the Fragment’s layout

These files contain only the onCreateView() method to inflate the UI of the fragment and returns the root of the fragment layout. If the fragment does not have any UI, it will return null. Each fragment has its own life cycle methods that is affected by activity life cycle because fragments are embedded in activity. Android fragment lifecycle is affected by activity lifecycle because fragments are included in activity. Android fragments have their own life cycle very similar to an android activity.

As you can see, you can refer to your TextView by using the bound layout reference. For the layout class, specify the name of the layout, followed by the type of layout, using a camel case syntax. With the introduction of the Android Jetpack, the old way of referencing views has been updated.

To add a Fragment statically to an Activity so that it is displayed for the entire lifecycle of the Activity, declare the Fragment inside the layout file for the Activity using the tag. You can specify layout attributes for the Fragment as if it were a View. Now that the basic structure of the two fragments has been implemented, they are ready to be embedded in the application’s main activity. The next step is to create the user interface for the first fragment that will be used within our activity. The lifecycle of android fragment is like the activity lifecycle. OnCreateView() The system calls this callback when it’s time for the fragment to draw its user interface for the first time.

Here we will design the basic simple UI by using TextView and Button in both xml’s. The base class for all activities using compatibility based Fragment features. Fragments has its own layout and its own behaviour with its own life cycle callbacks.