retrieve data from an existing database and display it in a textview in android with example

Android is an operating system that utilizes a SQLite database for managing data locally on mobile phones and other devices. SQLite is a widely-used database management system that is lightweight and easy to implement. Retrieving data from an existing database and displaying it in a TextView in Android is a common task for mobile app developers.

In this article, we will discuss how to retrieve data from an existing database and display it in a TextView in Android with an example.

Step 1: Create a new project in Android Studio

The first step is to create a new Android project in Android Studio. Open Android Studio and click on "Start a new Android Studio project". Follow the wizard to select the target devices, minimum SDK version, and other project settings.

Step 2: Add SQLite database to the project

Next, we need to add SQLite database to the project. Right-click on the project in the Project panel and select "New" -> "Folder" -> "Database". Give the new folder a name and click on "Finish".

Now, right-click on the newly created folder and select "New" -> "Database file". Give the database file a name and click on "Finish". The new database file will be added to the project.

Step 3: Create a database schema

The next step is to create a database schema. A database schema is a set of rules that define the structure and relationships of data in a database. In Android, we can create a schema using the SQLiteOpenHelper class.

Create a new class named "DatabaseHelper" and extend the SQLiteOpenHelper class. In the constructor, we need to pass the database name and version. Override the onCreate() and onUpgrade() methods to create and upgrade the database schemas respectively.

public class DatabaseHelper extends SQLiteOpenHelper {

private static final String DATABASE_NAME ="mydatabase.db";
private static final int DATABASE_VERSION = 1;

public DatabaseHelper(Context context) 
{
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) 
{
    db.execSQL("CREATE TABLE mytable (_id INTEGER PRIMARY KEY, name TEXT, age TEXT);");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
{
    db.execSQL("DROP TABLE IF EXISTS mytable");
    onCreate(db);
}

}

Step 4: Insert data into the database

Now we need to insert some data into the database. In the activity class, create an instance of the DatabaseHelper class and get the writable database. Then we can use the ContentValues class to insert data into the database.

public class MainActivity extends AppCompatActivity {

private MyAdapter mAdapter;

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

    mAdapter = new MyAdapter(this);

    ListView listView = findViewById(R.id.list_view);
    listView.setAdapter(mAdapter);

    DatabaseHelper dbHelper = new DatabaseHelper(this);
    SQLiteDatabase db = dbHelper.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put("name", "John");
    values.put("age", "25");
    db.insert("mytable", null, values);

    values = new ContentValues();
    values.put("name", "Mary");
    values.put("age", "30");
    db.insert("mytable", null, values);

    db.close();
}

}

Step 5: Retrieve data from the database

The next step is to retrieve data from the database. In the MyAdapter class, we can use the SQLiteDatabase.query() method to retrieve data from the database. We can specify the table name, columns to retrieve, selection, and sort order.

public class MyAdapter extends BaseAdapter
{
private final Context mContext;
private Cursor mCursor;

public MyAdapter(Context context) 
{
    mContext = context;

    DatabaseHelper dbHelper = new DatabaseHelper(context);
    SQLiteDatabase db = dbHelper.getReadableDatabase();

    String[] projection = { "_id", "name", "age" };
    mCursor = db.query("mytable", projection, null, null, null, null, null);
}

@Override
public int getCount() 
{
    return mCursor.getCount();
}

@Override
public Object getItem(int position) 
{
    mCursor.moveToPosition(position);

    String name = mCursor.getString(mCursor.getColumnIndex("name"));
    String age = mCursor.getString(mCursor.getColumnIndex("age"));

    return name + ", " + age;
}

@Override
public long getItemId(int position) 
{
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) 
{
    TextView textView = new TextView(mContext);
    textView.setText((String) getItem(position));
    return textView;
}

}

Step 6: Display the data in a TextView

Finally, we need to display the data in a TextView. In the activity class, we can create a TextView and set its text to the value retrieved from the database.

DatabaseHelper dbHelper = new DatabaseHelper(this);
SQLiteDatabase db = dbHelper.getReadableDatabase();

String[] projection = { "_id", "name", "age" };
Cursor cursor = db.query("mytable", projection, null, null, null, null, null);
cursor.moveToFirst();

TextView textView = findViewById(R.id.text_view);
textView.setText(cursor.getString(cursor.getColumnIndex("name")));

cursor.close();
db.close();

Conclusion

Retrieving data from an existing database and displaying it in a TextView in Android is a common task for mobile app developers. In this article, we have discussed how to retrieve data from an existing database and display it in a TextView in Android with an example. By using the SQLiteOpenHelper class, we can create database schemas and retrieve data from the database. We have used ContentValues class to insert data into the database and query() method to retrieve data. Finally, we have displayed the data in a TextView.

here are some additional details and tips on the topics we've covered:

Creating a New Android Project in Android Studio

  • When creating a new Android project in Android Studio, you will be presented with a few options and settings to configure. These include the project name, package name, target devices, minimum API level, and activity template. Make sure to choose these settings carefully, as they will determine the foundation of your app.

Adding SQLite Database to the Project

  • SQLite is included in the Android platform and is a popular choice for local data storage in Android apps. To add a SQLite database to your Android project, you can create a new folder in the project hierarchy and name it "database". Then, right-click on the "database" folder and choose "New" > "Database file". Enter a name for the database and click "Finish".

Creating a Database Schema

  • A database schema is the structure of a database, including tables, fields, and relationships. In Android, you can create a database schema using the SQLiteOpenHelper class. This class provides methods to create, upgrade, and manage a SQLite database. You can define the database schema in the onCreate() method and handle schema upgrades in the onUpgrade() method.

Inserting Data into the Database

  • After creating a database schema, you may want to insert some initial data into it. In Android, you can use the SQLiteDatabase.insert() method to insert data into a table. This method takes three parameters: the table name, a ContentValues object containing the data to insert, and an optional conflict resolution strategy.

Retrieving Data from the Database

  • To retrieve data from a SQLite database in Android, you can use the SQLiteDatabase.query() method. This method takes several parameters, including the table name, columns to retrieve, selection criteria, sorting order, and more. The method returns a Cursor object that you can iterate over to access the retrieved data.

Displaying Data in a TextView

  • Once you have retrieved data from a database in Android, you can display it in a TextView or other UI component. To display text in a TextView, you can call the setText() method of the TextView object and pass it a String value.

I hope these additional details are helpful!

Popular questions

  1. What is the purpose of SQLite database in Android?
    Answer: The SQLite database in Android is used for local data storage in mobile apps. It is a lightweight and easy-to-implement database management system that stores data in a structured manner.

  2. How do you add a SQLite database to an Android project?
    Answer: To add a SQLite database to an Android project, you can create a new folder called "database" within the project hierarchy and add a new database file to it. The database file extension is typically .db.

  3. How do you retrieve data from a SQLite database in Android?
    Answer: You can retrieve data from a SQLite database in Android using the SQLiteDatabase.query() method. This method takes several parameters, including the table name, columns to retrieve, selection criteria, sorting order, and more, and returns a Cursor object that you can iterate over to access the retrieved data.

  4. Can you explain what a database schema is in Android?
    Answer: A database schema in Android is the structure of a database, including tables, fields, and relationships. An Android app usually defines its database schema using the SQLiteOpenHelper class, which provides methods to create, upgrade, and manage a SQLite database.

  5. How do you display data retrieved from a database in a TextView in Android?
    Answer: To display data retrieved from a database in a TextView in Android, you can simply call the setText() method of the TextView object and pass it a String value. Alternatively, you can create a custom adapter class that extends BaseAdapter and handles the data retrieval and view creation for a ListView or other similar UI component.

Tag

Datafetching

As a senior DevOps Engineer, I possess extensive experience in cloud-native technologies. With my knowledge of the latest DevOps tools and technologies, I can assist your organization in growing and thriving. I am passionate about learning about modern technologies on a daily basis. My area of expertise includes, but is not limited to, Linux, Solaris, and Windows Servers, as well as Docker, K8s (AKS), Jenkins, Azure DevOps, AWS, Azure, Git, GitHub, Terraform, Ansible, Prometheus, Grafana, and Bash.

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