{"id":75670,"date":"2020-02-08T14:23:32","date_gmt":"2020-02-08T08:53:32","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=75670"},"modified":"2021-08-25T13:55:47","modified_gmt":"2021-08-25T08:25:47","slug":"android-fragment","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/android-fragment\/","title":{"rendered":"Android Fragment Tutorial – A Comprehensive Guide for Beginners"},"content":{"rendered":"

Moving further in our series of Android tutorials, now, it’s the turn for Android fragment. In this tutorial, we will learn about the working of Android fragment, its types, lifecycle, methods, and an example. In addition to this, we will also understand the process of adding fragments to activities, communication between fragment and activity and adding fragments within a fragment.<\/p>\n

Let’s start with a basic understanding of fragments.<\/p>\n

What is Android Fragment?<\/h3>\n

Android Fragment is a Graphical User Interface component of Android. It resides within the Activities<\/a><\/strong><\/em> of an Android application. It represents a portion of UI that the user sees on the screen. Android Fragments cannot exist outside an activity. Another name for Fragment can be Sub-Activity<\/strong> as they are part of Activities.<\/p>\n

Fragments<\/strong> can be dynamically added and removed as per the requirements. Fragments improve the adaptability & user experience by making the UI flexible for all devices. All the Fragments contain their own Events.<\/p>\n

Fragments generally provide us with a more flexible and wide range of options to make our Application more interactive. It can make different types of tab displays like scrolling, fixed or swiping tab. It also makes customizable action bars.<\/p>\n

To understand how a fragment interacts with the Activity, consider the following:<\/p>\n

\"android<\/a><\/p>\n

Types of Android Fragments<\/h3>\n

1. Single Fragments<\/h4>\n

Single fragments show only a single view for the user on the screen. These are for handheld devices such as mobile phones.<\/p>\n

2. List Fragments<\/h4>\n

List fragments are those that have a special list view feature. In this, there\u2019s a list and the user can choose to see a Sub-Activity.<\/p>\n

3. Fragment Transactions<\/h4>\n

Fragment transactions are for the transition from one fragment to another. It supports switching between two fragments.<\/p>\n

How Fragment Interacts with Activity in Different Devices<\/h3>\n

\"android<\/a><\/p>\n

The above image depicts two devices; a Handset and a Tablet. Come we\u2019ll understand both their functions:<\/p>\n

In tablets, there is only one activity that is Activity 1. In Activity 1<\/strong>, there are two fragments, Fragment A<\/strong> and Fragment B<\/strong>. When we select an item from Fragment A, it gets open in Fragment B of the same activity.<\/p>\n

In the case of mobiles, there are two activities that are:<\/p>\n

Activity 1<\/strong> with Fragment A<\/strong> and Activity 2<\/strong> with Fragment B<\/strong>.<\/p>\n

When we select an item from Fragment A<\/strong>, it gets open in the Fragment B<\/strong> of Activity 2<\/strong>.<\/p>\n

Android Fragment Lifecycle<\/h2>\n

The lifecycle of Android fragments strongly depends on the activity lifecycle and is similar to it. The fragment lifecycle is shown below:<\/p>\n

\"android<\/a><\/p>\n

Methods of Android Fragment<\/h3>\n

Our fragment class needs to implement the following methods for the fragments to work properly. Let us see them one by one:<\/p>\n

1. onAttach<\/h4>\n

This method executes only once during the whole implementation that is when the fragment attaches to an Activity.<\/p>\n

2. onCreate(Bundle)<\/h4>\n

This method is to create a Fragment. This is an important phase of implementation and all the attributes and components need to be added in this method itself.<\/p>\n

3. onCreateView()<\/h4>\n

The system invokes this method when we need to create the user interface of the fragment. It is called when the UI first initializes and later when the fragment returns back from the back stack.<\/p>\n

4. onActivityCreated()<\/h4>\n

The system invokes this method when an activity is created. During this, we can even access the fragments\u2019 view using the methods findViewById()<\/strong>.<\/p>\n

5. onViewStateRestored()<\/h4>\n

It provides the fragments with the information that all the saved states of fragment view are restored.<\/p>\n

6. onStart()<\/h4>\n

The system invokes the onStart() method when the fragment is visible on the user\u2019s device. This method makes the fragments visible.<\/p>\n

7. onResume()<\/h4>\n

This method makes the fragment interactive, which is on the user\u2019s device.<\/p>\n

8. onPause()<\/h4>\n

It\u2019s invoked when the fragment is no longer interactive and the user is about to leave it.<\/p>\n

9. onStop()<\/h4>\n

The system calls this method when the fragment is no longer visible on the user\u2019s device.<\/p>\n

10. onDestroyView()<\/h4>\n

When a fragment is about to get destroyed, the system calls this method to destroy it. It allows the fragment to clean up all the resources.<\/p>\n

11. onDestroy()<\/h4>\n

This method is the final clean up of the fragment\u2019s lifecycle. It allows the fragment to clean up the fragment state.<\/p>\n

12. onDetach()<\/h4>\n

It is to detach the fragment from the activity. With the execution of this method, the fragment is no longer associated with the host Activity.<\/p>\n

Android Fragment Example<\/h3>\n

Given below is a proper example of Android Fragments and Activity:<\/p>\n

\"android<\/a><\/p>\n

The above picture shows the Fragments on the main activity of Gmail.<\/p>\n

When we click on one of the options there like primary, snoozed, sent, or some other, another Fragment opens. For example, when we click on Scheduled the following Activity comes up:<\/p>\n

\"android<\/a><\/p>\n

Adding Fragments with Activities<\/h3>\n

Embedding Fragments with Activities means adding the Fragments to the respective Activity Layout. To embed any Fragments first ensure that the Activity extends FragmentActivity<\/strong> or AppCompatActivity<\/strong>. Now, there are two ways for adding multiple Fragments in one Activity:<\/p>\n

1. Statically<\/h4>\n

To add the fragment statically, we need to mention it ourselves in the activity_main.xml<\/strong> file. For example:<\/strong><\/p>\n

<?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n<LinearLayout xmlns:android=\"http:\/\/schemas.android.com\/apk\/res\/android\"\r\n    android:layout_width=\"match_parent\"\r\n    android:layout_height=\"match_parent\"\r\n    android:orientation=\"vertical\" >\r\n\r\n    <fragment\r\n        android:name=\"com.DataFlair.android.MyFragment\"\r\n        android:id=\"@+id\/MyFragment\"\r\n        android:layout_width=\"match_parent\" \r\n        android:layout_height=\"match_parent\" \/>\r\n\r\n<\/LinearLayout><\/pre>\n
These fragments can\u2019t be replaced during the execution as they are static.<\/p>\n
2. Dynamically<\/h4>\n
This is another method for embedding Fragments with activities. In this, we embed our Fragment in Activities dynamically using FragmentManager<\/strong>. For example:<\/strong><\/p>\n
<?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n<LinearLayout xmlns:android=\"http:\/\/schemas.android.com\/apk\/res\/android\"\r\n    android:layout_width=\"match_parent\"\r\n    android:layout_height=\"match_parent\"\r\n    android:orientation=\"vertical\" >\r\n  <FrameLayout\r\n       android:id=\"@+id\/df_placeholder\"\r\n       android:layout_width=\"match_parent\"\r\n       android:layout_height=\"match_parent\">\r\n  <\/FrameLayout>\r\n<\/LinearLayout><\/pre>\n
Unlike Static Fragment, in this, we can add, remove or replace the Fragments at the runtime itself. We create FragmentTransaction<\/strong> for this.<\/p>\n
We\u2019ll create FragmentTransaction as follows:<\/p>\n
FragmentTransaction F_T =getSupportFragmentManager().beginTransaction();\r\nF_T.replace(R.id.df_placeholder, new DataFlairFragment());\r\nF_T.commit();<\/pre>\n
Finding Fragment Instance<\/h3>\n
We can look up for Fragment within an Activity layout. For this, we use any one of the following ways:<\/p>\n