Source Code of MainAcivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button save = (Button) findViewById(R.id.save);
    Button display = (Button) findViewById(R.id.display);
    final EditText et1 = (EditText) findViewById(R.id.txtname);

    save.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            try {
                FileOutputStream fileout=openFileOutput("mytextfile.txt", MODE_PRIVATE);
                OutputStreamWriter outputWriter=new OutputStreamWriter(fileout);
                outputWriter.write(et1.getText().toString());
                outputWriter.close();

                //display file saved message
                Toast.makeText(getBaseContext(), "File is saved successfully!",
                        Toast.LENGTH_SHORT).show();

            } catch (Exception e) {
                e.printStackTrace();
            }




        }
    });
    display.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            try {
                FileInputStream fileIn=openFileInput("mytextfile.txt");
                InputStreamReader InputRead= new InputStreamReader(fileIn);

                char[] inputBuffer= new char[200];
                String s="";
                int charRead;

                while ((charRead=InputRead.read(inputBuffer))>0) {
                    // char to string conversion
                    String readstring=String.copyValueOf(inputBuffer,0,charRead);
                    s +=readstring;
                }
                InputRead.close();
                if(s.equals("")) {
                    Toast.makeText(getBaseContext(), "Content is not available in the file",
                            Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(getBaseContext(), "Contents in the file\n" + s,
                            Toast.LENGTH_SHORT).show();
                }


            } catch (Exception e) {
                e.printStackTrace();
            }




        }
    });
}

Source Code of activity_main.xml

<?xml version="1.0" encoding="utf-8"?>


<ScrollView xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_height="match_parent" android:layout_width="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".MainActivity">

        <TextView
            android:id="@+id/textView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Enter Username"
            android:textAlignment="center"
            android:textAppearance="@style/TextAppearance.AppCompat.Body2"
            android:layout_marginTop="20dp"
            android:textSize="25sp"
            android:textColor="@android:color/holo_blue_light" />

        <EditText
            android:id="@+id/txtname"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="20"
            android:hint="Enter Name"
            android:layout_marginLeft="40dp"
            android:layout_marginRight="40dp"
            android:layout_marginTop="10dp"
            android:inputType="textPersonName"
            />

        <Button
            android:id="@+id/save"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="40dp"
            android:layout_marginTop="40dp"
            android:layout_marginRight="40dp"
            android:layout_marginBottom="10dp"
            android:background="@color/colorAccent"
            android:text="SAVE"
            android:textColor="@android:color/white"
            android:textSize="25sp" />
        <Button
            android:id="@+id/display"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="40dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="40dp"
            android:layout_marginBottom="70dp"
            android:background="@color/colorAccent"
            android:text="DISPLAY"
            android:textColor="@android:color/white"
            android:textSize="25sp" />
        <TextView
            android:id="@+id/textView1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Developed By : w3techblog.com"
            android:textAlignment="center"
            android:textAppearance="@style/TextAppearance.AppCompat.Body2"
            android:layout_marginTop="20dp"
            android:textSize="25sp"
            android:textColor="@android:color/holo_blue_light" />
    </LinearLayout>
</ScrollView>

​

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