android - Androidでsqliteテーブルの内容を表示できませんか?

Question

私のアプリケーションには、挿入、更新、および表示操作を実行したい「出席」というテーブルがあります。

現在、表示ボタンをクリックすると、すべてのエントリが挿入されたテーブルではなく、空のテーブルが表示されるようになりました。誰かが私を助けてくれますか?

public class Update extends Activity {
Button b1,b2,b3;
EditText e1,e2,e3;
AttendanceDataBaseAdapter adb;
SQLiteDatabase db;
DataBaseHelper dbh;
TextView tv1;
   @Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.update);
    adb= new AttendanceDataBaseAdapter(this);
    adb=adb.open();
    b1=(Button)findViewById(R.id.insert);
    b2=(Button)findViewById(R.id.update);
    b3=(Button)findViewById(R.id.show);
    e1=(EditText)findViewById(R.id.entryforroll);
    e2=(EditText)findViewById(R.id.entryforname);
    e3=(EditText)findViewById(R.id.entryforpercentage);
    final String roll=e1.getText().toString();
    final String name=e2.getText().toString();
    final String percent=e3.getText().toString();


      //insert operation
    b1.setOnClickListener(new OnClickListener() {
    @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            adb.insertEntry(roll,name,percent);

        }
    });
       //update operation
    b2.setOnClickListener(new OnClickListener() {
    @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            adb.updateEntry(roll,name,percent);
    }
    });

     //show operation in table format
   b3.setOnClickListener(new OnClickListener() {

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    Cursor c=adb.getAll();
     int count= c.getCount();
    c.moveToFirst();
    TableLayout tableLayout = new TableLayout(getApplicationContext());
    tableLayout.setVerticalScrollBarEnabled(true);
   TableRow tableRow;
   TextView textView,textView1,textView2,textView3,textView4,textView5;
   tableRow = new TableRow(getApplicationContext());
   textView=new TextView(getApplicationContext());
   textView.setText("Roll Number");
   textView.setTextColor(Color.RED);
    textView.setTypeface(null, Typeface.BOLD);
     textView.setPadding(20, 20, 20, 20);
    tableRow.addView(textView);
    textView4=new TextView(getApplicationContext());
    textView4.setText("Name");
    textView4.setTextColor(Color.RED);
    textView4.setTypeface(null, Typeface.BOLD);
     textView4.setPadding(20, 20, 20, 20);
    tableRow.addView(textView4);
    textView5=new TextView(getApplicationContext());
    textView5.setText("Percent");
    textView5.setTextColor(Color.RED);
    textView5.setTypeface(null, Typeface.BOLD);
    textView5.setPadding(20, 20, 20, 20);
    tableRow.addView(textView5);
   tableLayout.addView(tableRow);
     for (Integer j = 0; j < count; j++)
     {
         tableRow = new TableRow(getApplicationContext());
         textView1 = new TextView(getApplicationContext());
         textView1.setText(c.getString(c.getColumnIndex("ROLLNO")));
         textView2 = new TextView(getApplicationContext());
         textView2.setText(c.getString(c.getColumnIndex("STUNAME")));
         textView3 = new TextView(getApplicationContext());
         textView3.setText(c.getString(c.getColumnIndex("PERCENTAGE")));
         textView1.setPadding(20, 20, 20, 20);
         textView2.setPadding(20, 20, 20, 20);
         textView3.setPadding(20, 20, 20, 20);
         tableRow.addView(textView1);
         tableRow.addView(textView2);
         tableRow.addView(textView3);
         tableLayout.addView(tableRow);
         c.moveToNext() ;
     }
     setContentView(tableLayout);       

AttendanceDataBaseAdapter :

 public class AttendanceDataBaseAdapter 
 {

 public final String DATABASE_NAME="grietportal.db";
 static final int DATABASE_VERSION=2;
 static final int NAME_COLUMN=1;
 public SQLiteDatabase db;
 private final Context context;
 private DataBaseHelper dbhelper;
 public AttendanceDataBaseAdapter(Context _context)
  {
     context=_context;
     dbhelper=new DataBaseHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
   }
  public AttendanceDataBaseAdapter open() throws SQLException
   {
    db=dbhelper.getWritableDatabase();
    return this;
   }
public void close()
{
     db.close();
}
public SQLiteDatabase getDatabaseInstance()
{
    return db;
}
 //insert 
public void insertEntry(String roll,String name,String percent)
{
    db=dbhelper.getWritableDatabase();
    ContentValues newcontent=new ContentValues();
    newcontent.put("ROLLNO",roll);
    newcontent.put("STUNAME", name);
    newcontent.put("PERCENTAGE",percent);

    db.insert("ATTENDANCE", null, newcontent);

    db.close();
}
 //update

public void updateEntry(String roll,String name,String percent)
{

    db=dbhelper.getWritableDatabase();
    ContentValues newupdate=new ContentValues();
    newupdate.put("ROLLNO", roll);
    newupdate.put("STUNAME",name);
    newupdate.put("PERCENTAGE", percent);

    String where="ROLLNO=?";
    db.update("ATTENDANCE", newupdate, where, new String[] {roll});
    db.close();

}
//show
public Cursor getAll()  {
    db=dbhelper.getWritableDatabase();
    return db.query("ATTENDANCE", new String[] {"ROLLNO","STUNAME",
            "PERCENTAGE"}, null, null, null, null, null);
}


}