SQLite Read

MainActivity.java

import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
 public class MainActivity extends AppCompatActivity {
  DataBaseHelper myDb;
  TextView txtResult;
  Button btnClick;
  @Override 
   protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   myDb = new DataBaseHelper(this);
   txtResult = (TextView) findViewById(R.id.idResult);
   btnClick = (Button) findViewById(R.id.idBtn);
   btnClick.setOnClickListener(new View.OnClickListener() {
   @Override 
    public void onClick(View v) {
     ClickMe();
   }
  });
 }
  private void ClickMe() {
   Cursor res = myDb.getAllData();
   StringBuffer stringBuffer = new StringBuffer();
  
  if (res != null && res.getCount() > 0) {
   
   while (res.moveToNext()) {
     stringBuffer.append("Id: " + res.getString(0) + "\n");
     stringBuffer.append("Name: " + res.getString(1) + "\n");
     stringBuffer.append("Surname: " + res.getString(2) + "\n");
     stringBuffer.append("Marks: " + res.getString(3) + "\n" + "\n");
    
   }
    txtResult.setText(stringBuffer.toString());
    Toast.makeText(this, "Data Retrieved Successfully", Toast.LENGTH_SHORT).show();
   
  } else {
    Toast.makeText(this, "No Data to Retrieve", Toast.LENGTH_SHORT).show();
   
  }
 }
}

DBHelper.java

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

  public class DataBaseHelper extends SQLiteOpenHelper {
  public static final String DATABASE_NAME = "Student.db";
  public static final String TABLE_NAME = "Student_table";
  public static final String COL_1 = "ID";
  public static final String COL_2 = "NAME";
  public static final String COL_3 = "SURNAME";
  public static final String COL_4 = "MARKS";
  public DataBaseHelper(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,SURNAME TEXT,MARKS INTEGER)");
  
 }
  @Override 
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
   db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
  }
 public Cursor getAllData() {
   SQLiteDatabase db = this.getWritableDatabase();
   Cursor res = db.rawQuery("Select * from " + TABLE_NAME, null);
  return res;
 }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent" 
     android:layout_height="match_parent"
     android:paddingBottom="@dimen/activity_vertical_margin" 
     android:paddingLeft="@dimen/activity_horizontal_margin" 
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin" 
     tools:context="anu.com.sqlite.MainActivity" 
     android:orientation="vertical"> 
    
    <Button 
     android:id="@+id/idBtn" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:text="READ" />  
    
    <TextView 
     android:id="@+id/idResult"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:textSize="25sp"/>
</LinearLayout> ​ 

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Author : Android Code Tutorial