StudentsDb1 Example

Goal:

Create an SQLite database, insert one row into it. Then retrieve the row from the database and display the fields on a textfield.

Directions:

Create an Android Studio project with name StudentsDb1 and package it372.studentsdb1.
Leave the layout and TextView widget containing "Hello, World." as is.
Set the id of this TextView widget to txt_output.

Create this StudentsDBHelper class derived from SQLiteOpenHelper:

package it372.smiths.studentsdb1;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class StudentsDBHelper bextends SQLiteOpenHelper {
    private static final String DB_NAME = "students.db";
    private static final int DB_VERSION = 1;

    public StudentsDBHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table students(" +
            "name text, grade integer, gender text);");
        insertStudent(db, "Alice", 6, "female");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db,
        int oldVersion, int newVersion) {
        // Body to be added later.
    }

    private static void insertStudent(SQLiteDatabase db,
        String name, int grade, String gender) {

        ContentValues studentValues = new ContentValues( );
        studentValues.put("name", name);
        studentValues.put("grade", grade);
        studentValues.put("gender", gender);
        db.insert("students", null, studentValues);
    }
}

Add this Java code to the onCreate method of the MainActivity.java class:

TextView txtOutput = findViewById(R.id.txt_output);
SQLiteOpenHelper dbh = new StudentsDBHelper(this);
try {
    SQLiteDatabase db = dbh.getReadableDatabase();
    Cursor cursor = db.query("students", 
        new String[ ] {"name", "grade", "gender"},
        null, null, null, null, null) ;
    if (cursor.moveToLast()) {
        String name = cursor.getString(0);
        int grade = cursor.getInt(1);
        String gender = cursor.getString(2);
        String output = String.format("%s %d %s",
            name, grade, gender);
           
       // This statement writes to the Logcat window.     
       // Log.i("111", output);
                
       // This statement writes to the Run window.
       // System.out.println(output);
       
       // Display output in txt_output TextView widget.
       txtOutput.setText(output);
   }
}
        
catch(SQLiteException e) {
    Toast toast = Toast.makeText(this, 
        "Database not created.",
        Toast.LENGTH_LONG);
}

Run the app to test it.
Locate the database using the Device File Explorer:
View >> Tool Windows >> Device File Explorer
Find the students.db database:
```
/data/data/it372/ssmiths/studentsdb1/databases/students.db
```

Here are the source code files:
activity_main.xml MainActivity.java StudentsDBHelper.java