o7planning

Android Fragments Tutorial

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1- What is Android Fragment?

To design an interface, you can design fragments and put it together. In this example, I will guide you to work with the fragment.
And process event which interacts between 2 fragment.

2- Android Fragment Example

Create a Project named AndroidFragmentDemo
Prepare an image file, such as:
  • andrea.png
Copy and paste andrea.jpg file to mipmap folder of project
Android Studio will require you to choose imagine quality that will be created. Select mipmap-mdpi as this is the average image quality.
Next we create activity_top.xml file:
In Android Studio select:
  • File > New > Layout Resource file
Enter:
  • File name: activity_top.xml
  • Root element: androidx.constraintlayout.widget.ConstraintLayout
  • Directory name: layout
Similarly create activity_bottom.xml file.

Design Interface on activity_top.xml

activity_top.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/editText_firstName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="20dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText_lastName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="23dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText_firstName" />

    <Button
        android:id="@+id/button_apply"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="22dp"
        android:text="Apply"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText_lastName" />
</androidx.constraintlayout.widget.ConstraintLayout>

Design Interface on activity_bottom.xml

activity_bottom.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@mipmap/andrea">

    <TextView
        android:id="@+id/textView_fullName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:background="#EDE4E4"
        android:text="Full Name"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
If you are interested in the steps to design the interface of this application, see the appendix at the end of the article.
Each fragment will correspond to a Java class. This class is extended from Fragment class
Create 2 class: TopFragment and BottomFragment and edit its code.
TopFragment .java
package org.o7planning.androidfragmentdemo;

import android.content.Context;
import android.os.Bundle;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class TopFragment extends Fragment {

    private EditText editTextFirstName;
    private EditText editTextLastName;
    private Button buttonApply;

    private MainActivity mainActivity;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {


        // Read xml file and return View object.
        // inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot)
        View view = inflater.inflate(R.layout.activity_top, container, false);

        editTextFirstName = (EditText) view.findViewById(R.id.editText_firstName);
        editTextLastName = (EditText) view.findViewById(R.id.editText_lastName);

        buttonApply = (Button) view.findViewById(R.id.button_apply);

        buttonApply.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                applyText();
            }
        });

        return view;
    }

    // Called when a fragment is first attached to its context.
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        if (context instanceof MainActivity) {
            this.mainActivity = (MainActivity) context;
        }
    }


    private void applyText() {
        String firstName = this.editTextFirstName.getText().toString();
        String lastName = this.editTextLastName.getText().toString();

        this.mainActivity.showText(firstName, lastName);
    }
}
BottomFragment.java
package org.o7planning.androidfragmentdemo;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class BottomFragment extends Fragment {

    private TextView textViewFullName;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        // Read xml file and return View object.
        // inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot)
        View view = inflater.inflate(R.layout.activity_bottom, container, false);

        textViewFullName = (TextView) view.findViewById(R.id.textView_fullName);

        return view;
    }


    public void showText(String firstName, String lastName) {
        textViewFullName.setText(firstName + " " + lastName);
    }
}
Now, you need to arrange the fragment on the main interface of the Activity. Open activity_main.xml file 
Set ID for fragments.
  • fragment_top
  • fragment_bottom
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <fragment
        android:id="@+id/fragment_top"
        android:name="org.o7planning.androidfragmentdemo.TopFragment"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <fragment
        android:id="@+id/fragment_bottom"
        android:name="org.o7planning.androidfragmentdemo.BottomFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment_top" />
</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity.java
package org.o7planning.androidfragmentdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void showText(String topImageText, String bottomImageText) {
        BottomFragment bottomFragment
                = (BottomFragment) this.getSupportFragmentManager()
                .findFragmentById(R.id.fragment_bottom);
        bottomFragment.showText(topImageText, bottomImageText);
    }

}

 
Running Apps:

3- Appendix: Interface design - activity_top.xml

activity_top.xml

Set ID, Text for components on the interface:

4- Appendix: Interface design - activity_bottom.xml

activity_bottom.xml

Set ID, Text for components on the interface.

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