edit text에 입력한 내용을 저장할려고 하는데 숫자는 입력이되는데 문자를 넣으면 자꾸 꺼져버립니다..

도움을 부탁드립니다..

@Override
 protected void onCreate(Bundle savedInstanceState) {
  // TODO Auto-generated method stub
  super.onCreate(savedInstanceState);
  setContentView(R.layout.infosave);
  
  myInfoDB = new InfoDB(this);
  
  btnAdd   = (Button)findViewById(R.id.buttonAdd);
  btnUpdate = (Button)findViewById(R.id.buttonUpdate);
  btnDelete = (Button)findViewById(R.id.buttonDelete);
  
  btnAdd.setOnClickListener(this);
  btnUpdate.setOnClickListener(this);
  btnDelete.setOnClickListener(this);
 
 }// end of onCreate()

 @Override
 public void onClick(View v) {
  // TODO Auto-generated method stub
  
  db = myInfoDB.getWritableDatabase();
//  Cursor cursor;
  
  int tot=0;
  String str_line;
  
   /*cursor =  db.rawQuery("Select bun,balance,io from BankTable", null);
  
   ArrayList<String> ar = new ArrayList<String>();
  
   while(cursor.moveToNext())
   {
    String tmpId   = cursor.getString(0);
    String tmpName    = cursor.getString(1);
    String tmpNumber  = cursor.getString(2);
    String tmpEmail   = cursor.getString(3);
      
    str_line =
    String.format("%2s %10s %10s %10s", tmpName,tmpNumber,tmpEmail,String.valueOf(tot));    
    ar.add(str_line);
   
   }//end of while
   
   db.close();
  
  */
  
  switch(v.getId())
  {
  case R.id.buttonAdd :
   
   db = myInfoDB.getReadableDatabase();
   
   EditText editTextName = (EditText)findViewById(R.id.editName);
   String strName = editTextName.getText().toString();
   editTextName.setText("");
   
   EditText editTextNumber = (EditText)findViewById(R.id.editNumber);
   String strNumber = editTextNumber.getText().toString();
   editTextNumber.setText("");
   
   EditText editTextEmail = (EditText)findViewById(R.id.editEmail);
   String strEmail = editTextEmail.getText().toString();
   editTextEmail.setText("");

   
   db.execSQL("INSERT INTO MemberTable Values (null, "+ strName +" ,"+ strNumber +", "+ strEmail +"  );");
    
   db.close();
   
    Toast.makeText(this,"저장되었습니다.", Toast.LENGTH_LONG).show();
   
   break;
   
  case R.id.buttonUpdate :
   
   Intent intent = new Intent(InfoSave.this, TestList.class);
   startActivity(intent);
   
   break;
   
  case R.id.buttonDelete :
   
   break;
  }
 }// end of onClick()

}