Practical NO.26 : Perform Async Task using SQLite.
• activity_main.xml
<RelativeLayout android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/ android:layout_below="@id/button_add"
apk/res/android" android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"
xmlns:tools="http://schemas.android.com/to android:text="Show Data"/>
ols" <Button
android:layout_width="match_parent" android:id="@+id/button_reset_db"
android:layout_height="match_parent" android:layout_width="wrap_content"
tools:context=".MainActivity"> android:layout_height="wrap_content"
<EditText
android:id="@+id/editText" android:layout_below="@id/button_show_d
android:layout_width="match_parent" ata"
android:layout_height="wrap_content" android:layout_centerHorizontal="true"
android:hint="Enter data" android:layout_marginTop="16dp"
android:layout_margin="16dp"/> android:text="Reset DB"/>
<Button <ListView
android:id="@+id/button_add" android:id="@+id/listView"
android:layout_width="wrap_content" android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_height="match_parent"
android:layout_below="@id/editText"
android:layout_centerHorizontal="true" android:layout_below="@id/button_reset_db
android:layout_marginTop="16dp" "
android:text="Add Data"/> android:layout_marginTop="16dp"/>
<Button </RelativeLayout>
android:id="@+id/button_show_data"
android:layout_width="wrap_content"
• MainActivity.java
package com.example.twentysix; private Button buttonAdd,
buttonShowData, buttonResetDB;
import android.os.AsyncTask; private ListView listView;
import android.os.Bundle; private DatabaseHelper databaseHelper;
import android.view.View; private DataAdapter dataAdapter;
import android.widget.Button; private ArrayList<String> dataList;
import android.widget.EditText;
import android.widget.ListView; @Override
import android.widget.Toast; protected void onCreate(Bundle
savedInstanceState) {
import super.onCreate(savedInstanceState);
androidx.appcompat.app.AppCompatActivity; setContentView(R.layout.activity_main);
import java.util.ArrayList; editText = findViewById(R.id.editText);
buttonAdd =
public class MainActivity extends findViewById(R.id.button_add);
AppCompatActivity { buttonShowData =
private EditText editText; findViewById(R.id.button_show_data);
buttonResetDB =
findViewById(R.id.button_reset_db); doInBackground(String... params) {
listView = findViewById(R.id.listView); return
databaseHelper.insertData(params[0]);
databaseHelper = new }
DatabaseHelper(this);
dataList = new ArrayList<>(); @Override
dataAdapter = new DataAdapter(this, protected void onPostExecute(Boolean
dataList); result) {
listView.setAdapter(dataAdapter); if (result) {
Toast.makeText(MainActivity.this,
// Add Data Button "Data inserted successfully",
buttonAdd.setOnClickListener(new Toast.LENGTH_SHORT).show();
View.OnClickListener() { editText.setText("");
@Override } else {
public void onClick(View v) { Toast.makeText(MainActivity.this,
String data = "Failed to insert data",
editText.getText().toString().trim(); Toast.LENGTH_SHORT).show();
}
if (!data.isEmpty()) { }
new }
InsertDataTask().execute(data);
} else { // Fetch Data Task
private class FetchDataTask extends
Toast.makeText(MainActivity.this, "Please AsyncTask<Void, Void, ArrayList<String>>
enter data", Toast.LENGTH_SHORT).show(); {
} @Override
} protected ArrayList<String>
}); doInBackground(Void... voids) {
return databaseHelper.getAllData();
// Show Data Button }
buttonShowData.setOnClickListener(new @Override
View.OnClickListener() { protected void
@Override onPostExecute(ArrayList<String> result) {
public void onClick(View v) { if (result != null && !result.isEmpty())
new FetchDataTask().execute(); {
} dataList.clear();
}); dataList.addAll(result);
// Reset DB Button dataAdapter.notifyDataSetChanged();
buttonResetDB.setOnClickListener(new } else {
View.OnClickListener() { Toast.makeText(MainActivity.this,
@Override "No data found",
public void onClick(View v) { Toast.LENGTH_SHORT).show();
new }
ResetDatabaseTask().execute(); }
} }
});
} // Reset Database Task
private class ResetDatabaseTask extends
// Insert Data Task AsyncTask<Void, Void, Boolean> {
private class InsertDataTask extends @Override
AsyncTask<String, Void, Boolean> { protected Boolean
@Override doInBackground(Void... voids) {
protected Boolean return databaseHelper.resetDatabase();
} } else {
Toast.makeText(MainActivity.this,
@Override "Failed to reset database",
protected void onPostExecute(Boolean Toast.LENGTH_SHORT).show();
result) { }
if (result) { }
Toast.makeText(MainActivity.this, }
"Database reset successfully", }
Toast.LENGTH_SHORT).show();
dataList.clear();
dataAdapter.notifyDataSetChanged();
• DatabaseHelper.java
package com.example.twentysix; context) {
super(context, DATABASE_NAME,
import android.content.ContentValues; null, DATABASE_VERSION);
import android.content.Context; }
import android.database.Cursor;
import @Override
android.database.sqlite.SQLiteDatabase; public void onCreate(SQLiteDatabase
import db) {
android.database.sqlite.SQLiteOpenHelp
er; db.execSQL(CREATE_TABLE_QUERY)
;
import java.util.ArrayList; }
public class DatabaseHelper extends @Override
SQLiteOpenHelper { public void
onUpgrade(SQLiteDatabase db, int
private static final String oldVersion, int newVersion) {
DATABASE_NAME = "my_database"; db.execSQL("DROP TABLE IF
private static final int EXISTS " + TABLE_NAME);
DATABASE_VERSION = 1; onCreate(db);
}
private static final String
TABLE_NAME = "my_table"; public boolean insertData(String data)
private static final String {
COLUMN_ID = "id"; SQLiteDatabase db =
private static final String this.getWritableDatabase();
COLUMN_DATA = "data"; ContentValues values = new
ContentValues();
private static final String values.put(COLUMN_DATA, data);
CREATE_TABLE_QUERY = long result =
"CREATE TABLE " + db.insert(TABLE_NAME, null, values);
TABLE_NAME + " (" + return result != -1;
COLUMN_ID + " }
INTEGER PRIMARY KEY
AUTOINCREMENT," + public ArrayList<String> getAllData()
COLUMN_DATA + " {
TEXT)"; ArrayList<String> dataList = new
ArrayList<>();
public DatabaseHelper(Context SQLiteDatabase db =
this.getReadableDatabase(); return dataList;
Cursor cursor = }
db.rawQuery("SELECT * FROM " +
TABLE_NAME, null); public boolean resetDatabase() {
SQLiteDatabase db =
if (cursor.moveToFirst()) { this.getWritableDatabase();
do { db.execSQL("DELETE FROM " +
String data = TABLE_NAME);
cursor.getString(1); // Get data from db.execSQL("VACUUM"); //
column 1 Optional to optimize DB size
dataList.add(data); return true;
} while (cursor.moveToNext()); }
} }
cursor.close();
• DataAdapter.java
package com.example.twentysix;
@Override
import android.content.Context; public View getView(int position, View
import android.view.LayoutInflater; convertView, ViewGroup parent) {
import android.view.View; String data = getItem(position);
import android.view.ViewGroup;
import android.widget.ArrayAdapter; if (convertView == null) {
import android.widget.TextView; convertView =
LayoutInflater.from(getContext()).inflate(R.layout.list_
item, parent, false);
import java.util.ArrayList;
}
public class DataAdapter extends
TextView textView =
ArrayAdapter<String> {
convertView.findViewById(R.id.textViewItem);
public DataAdapter(Context context,
textView.setText(data);
ArrayList<String> dataList) {
return convertView;
super(context, 0, dataList);
}
}
}
• List_item.xml
<TextView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/textViewItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="16dp"
android:textSize="16sp"
android:textColor="#000000"/>
Output:
