SQLite - 将数据从数据库显示到警报对话框中会切断消息

Question

我正在尝试使用字符串缓冲区将SQLite数据库中的数据显示到警报对话框中，但是当我运行应用程序时，我收到了没有表中数据的消息。以下是我使用的两种方法（Users.java）：

 public void viewAll() { 
 btn2.setOnClickListener(
 new OnClickListener() {
    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        Cursor Res = db.getAllData();
        if(Res.getCount() == 0) {
            showMessage("Error" , "nothing found" );
            return;

        } 
         buffer = new StringBuffer();
                 while(Res.moveToNext()) { emailstring = Res.getString(0);
                 passstring = Res.getString(1);
            buffer.append("password : "+ emailstring + "\n");
            buffer.append("email : "+ passstring + "\n\n");
// when I run the app the alert dialog shows "password :" and "email :" just  
        }
     data = buffer.toString();
        showMessage("data", data);  
        } 
 }  );

} 
public void showMessage(String title,String Message)
{ 
    AlertDialog.Builder builder = new AlertDialog.Builder(Users.this);
    builder.setCancelable(true);
    builder.setTitle(title);
    builder.setMessage(Message);
    builder.show();
}

  //getAllData() (in databasehelper.java) :
public Cursor getAllData() { 
  SQLiteDatabase db = this.getWritableDatabase();

  Cursor Res = db.rawQuery("SELECT  * FROM " + TABLE_NAME  , null);
  return Res;
     }
}

插入数据库：

 public class Users extends Activity
 {
 EditText user; 
 EditText pass;
 String email;
 String pass2;
 Button btn2;
 Button btn;
 StringBuffer buffer;
 String data;
 String emailstring;
 String passstring;

 DBhelper2 db;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.user);
    user = (EditText) findViewById (R.id.emailadress);
    pass = (EditText) findViewById (R.id.passkelme);
     btn = (Button)findViewById(R.id.Button1);
      btn2 = (Button)findViewById(R.id.button2);
    email = user.getText().toString();
    pass2 = pass.getText().toString();
addData();      
viewAll();


} 
public void addData() {
btn.setOnClickListener(     new OnClickListener() {

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub

        // TODO Auto-generated method stub
     db = new DBhelper2(getApplicationContext());
        if(CheckifEmpty(user) == false && CheckifEmpty(pass) == false ) { 
            if(db.insertusers2(pass2, email) == true)
            {   Toast.makeText(getApplicationContext(), "data saved succesfully" , Toast.LENGTH_LONG).show();

            }
            else {  Toast.makeText(getApplicationContext(), "data saved not succesfully" , Toast.LENGTH_LONG).show();}
        }
        if(CheckifEmpty(user) == true || CheckifEmpty(pass) == true ) {
            Toast.makeText(getApplicationContext(), "error you must fill the 2 fields " , Toast.LENGTH_LONG).show();
        } 
    }

});
}

插入函数（databasehelper）：

public boolean insertusers2( String P ,String E )
 {
  SQLiteDatabase db = this.getWritableDatabase();
  ContentValues contentvalues = new ContentValues();

contentvalues.put(COLUMN_PASSWORD, P);
contentvalues.put(COLUMN_EMAIL, E);
if(db != null) {db.insert("tbldata", null, contentvalues);
return true;
}
return false;

}