How to Delete a Value from SQLite Database in Android app

For Creating SQLite Database Click Here
For Inserting in SQLite Database Click Here
For Displaying from SQLite Database Click Here
For Updating in SQLite Database Click Here

In this, We Delete value from our SQLite Database.

For that, we need a Unique Id and on behalf of that Id, we will delete values from Database.

Then create a Delete Button in MainActivity.XML

MainActivity.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <LinearLayout 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:orientation="vertical"  
   tools:context=".MainActivity">  
 <EditText  
   android:layout_width="match_parent"  
   android:layout_height="wrap_content"  
   android:id="@+id/name"  
   android:hint="name"  
   />  
   <EditText  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:id="@+id/marks"  
     android:hint="marks"  
     />  
   <EditText  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:id="@+id/ids"  
     android:hint="id"  
     />  
   <Button  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Insert"  
     android:id="@+id/Button"/>  
   <Button  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Show"  
     android:id="@+id/show"/>  
   <Button  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Update"  
     android:id="@+id/Update"/>  

   <Button  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Delete"  
     android:id="@+id/delete"/>  
 </LinearLayout>  

Here, We add a new Delete Button to Delete a value from Database.

Then, We create a new Delete Method in our DatabaseHelper.class

DatabaseHelper.class

 package harpreet.studio.mysqlitedatabase;  
 import android.app.ActionBar;  
 import android.content.ContentValues;  
 import android.content.Context;  
 import android.database.Cursor;  
 import android.database.sqlite.SQLiteDatabase;  
 import android.database.sqlite.SQLiteOpenHelper;  
 import android.provider.ContactsContract;  
 import androidx.annotation.Nullable;  
 public class DatabaseHelper extends SQLiteOpenHelper {  
   public static final String Database_name = "Students.db";  
   public static final String Table_name = "Student_table";  
   public static final String col_id = "Id";  
   public static final String col_name = "name";  
   public static final String col_marks = "marks";  
   public DatabaseHelper(@Nullable Context context) {  
     super(context, Database_name, null, 1);  
   }  
   @Override  
   public void onCreate(SQLiteDatabase db) {  
       db.execSQL("create table " + Table_name +" (Id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT , marks INTEGER)");  
   }  
   @Override  
   public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {  
       sqLiteDatabase.execSQL("DROP TABLE IF EXISTS "+Table_name);  
       onCreate(sqLiteDatabase);  
   }  
   public boolean insertData(String name,String marks)  
   {  
     SQLiteDatabase db = this.getWritableDatabase();  
     ContentValues cv = new ContentValues();  
     cv.put(col_name,name);  
     cv.put(col_marks,marks);  
     Long result = db.insert(Table_name,null,cv);  
     if(result == -1 )  
     {  
       return false;  
     }  
     else  
     {  
       return true;  
     }  
   }  
   public Cursor Showdata()  
   {  
     SQLiteDatabase db = this.getWritableDatabase();  
     Cursor cursor = db.rawQuery("select * from "+Table_name,null);  
     return cursor;  
   }  
   public boolean update(String id,String name,String marks)  
   {  
     SQLiteDatabase db = this.getWritableDatabase();  
     ContentValues cv = new ContentValues();  
     cv.put(col_id,id);  
     cv.put(col_name,name);  
     cv.put(col_marks,marks);  
     db.update(Table_name,cv,"Id = ?",new String[] { id });  
     return true;  
   }  

   public Integer delete(String id)  
   {  
     SQLiteDatabase db = this.getWritableDatabase();  
     return db.delete(Table_name,"Id = ?",new String[] {id});  
   }  
 }  

Here, We add a new Delete method to delete some values on behalf of Id.

Then we have to call that delete Button and create a Delete Method in our MainActivity.Java file

MainActivity.java

 package harpreet.studio.mysqlitedatabase;  
 import androidx.appcompat.app.AlertDialog;  
 import androidx.appcompat.app.AppCompatActivity;  
 import android.database.Cursor;  
 import android.os.Bundle;  
 import android.view.View;  
 import android.widget.Button;  
 import android.widget.EditText;  
 import android.widget.Toast;  
 public class MainActivity extends AppCompatActivity {  
   DatabaseHelper mydb;  
   EditText etname,etmarks,etid;  
   Button insertbtn,showbtn,updatebtn,deletebtn;  
   @Override  
   protected void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.activity_main);  
     mydb = new DatabaseHelper(this);  
     etname = findViewById(R.id.name);  
     etmarks = findViewById(R.id.marks);  
     etid = findViewById(R.id.ids);  
     insertbtn = findViewById(R.id.Button);  
     showbtn = findViewById(R.id.show);  
     updatebtn = findViewById(R.id.Update);  
     deletebtn = findViewById(R.id.delete);  
     insertdata();  
     showdata();  
     update();  
     delete();  
   }  
   public void insertdata()  
   {  
     insertbtn.setOnClickListener(new View.OnClickListener() {  
       @Override  
       public void onClick(View view) {  
         Boolean Inserted = mydb.insertData(etname.getText().toString(),etmarks.getText().toString());  
         if(Inserted)  
         {  
           Toast.makeText(MainActivity.this, "Data is Inserted", Toast.LENGTH_SHORT).show();  
         }  
         else  
         {  
           Toast.makeText(MainActivity.this, "Error Inserting", Toast.LENGTH_SHORT).show();  
         }  
       }  
     });  
   }  
   public void showdata()  
   {  
     showbtn.setOnClickListener(new View.OnClickListener() {  
       @Override  
       public void onClick(View view) {  
         Cursor cursor = mydb.Showdata();  
         if(cursor.getCount() == 0)  
         {  
           message("Error","No data");  
           return;  
         }  
         StringBuffer buffer = new StringBuffer();  
         while(cursor.moveToNext())  
         {  
           buffer.append("Id : " + cursor.getString(0)+"\n")  
               .append("Name : "+ cursor.getString(1)+"\n")  
               .append("marks : "+ cursor.getString(2)+"\n");  
         }  
           message("Data",buffer.toString());  
       }  
     });  
   }  
   public void update()  
   {  
     updatebtn.setOnClickListener(new View.OnClickListener() {  
       @Override  
       public void onClick(View view) {  
         Boolean updated = mydb.update(etid.getText().toString(),etname.getText().toString(),  
             etmarks.getText().toString());  
         if(updated)  
         {  
           Toast.makeText(MainActivity.this, "Updated", Toast.LENGTH_SHORT).show();  
         }  
         else  
         {  
           Toast.makeText(MainActivity.this, "Error in Updating", Toast.LENGTH_SHORT).show();  
         }  
       }  
     });  
   }  
   public void delete()  
   {  
     deletebtn.setOnClickListener(new View.OnClickListener() {  
       @Override  
       public void onClick(View view) {  
         Integer delete = mydb.delete(etid.getText().toString());  
         if(delete > 0)  
         {  
           Toast.makeText(MainActivity.this, "Data Deleted", Toast.LENGTH_SHORT).show();  
         }  
         else  
         {  
           Toast.makeText(MainActivity.this, "Data Not Deleted", Toast.LENGTH_SHORT).show();  
         }  
       }  
     });  
   }  
   public void message(String title,String message)  
   {  
     AlertDialog.Builder builder = new AlertDialog.Builder(this);  
     builder.setCancelable(true);  
     builder.setTitle(title)  
         .setMessage(message)  
         .show();  
   }  
 }  

Here, We create a new Delete method and pass the value of Id in that method.

For Creating SQLite Database Click Here
For Inserting in SQLite Database Click Here
For Displaying from SQLite Database Click Here
For Updating in SQLite Database Click Here
For Deleting from SQLite Database Click Here

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