protected async override void OnAppearing()
{
base.OnAppearing();
if (string.IsNullOrEmpty(RetrievedItemDataStore.Instance().id))
{
id.Text = "Retrieve records first";
timeStamp.Text = "Retrieve records first";
userName.Text = "Retrieve records first";
userEmail.Text = "Retrieve records first";
userPassword.Text = "Retrieve records first";
}
else
{
id.Text = RetrievedItemDataStore.Instance().id;
timeStamp.Text = RetrievedItemDataStore.Instance().savedTimeStamp;
userName.Text = RetrievedItemDataStore.Instance().name;
userEmail.Text = RetrievedItemDataStore.Instance().email;
userPassword.Text = RetrievedItemDataStore.Instance().password;
}
}
//******
public RetrieveViewModel()
{
////RegisterPersonCommand = new Command<string>(async (itemName) =>
//RegisterPersonCommand = new Command(async () =>
//{
// //if (string.IsNullOrEmpty(_userNameText))
// // _userNameText = "";
// //if (string.IsNullOrEmpty(_userEmailText))
// // _userEmailText = "";
// //if (string.IsNullOrEmpty(_userPasswordText))
// //_userPasswordText = "";
// Item itemToSave = new Item
// {
// Name = _userNameText,
// Email = _userEmailText,
// Password = _userPasswordText
// };
// //await Helpers.AwsDynamoDbHelper.Instance().SaveItemAsync(itemName);
// //await Helpers.AwsDynamoDbHelper.Instance().SaveItemAsync(_userNameText);
// IsBusy = true;
// await Helpers.AwsDynamoDbHelper.Instance().SaveItemAsync(itemToSave);
// IsBusy = !IsBusy;
//});
//RetrievePersonCommand = new Command(async () =>
//{
// IsBusy = true;
// await Helpers.AwsDynamoDbHelper.Instance().ReadItemAsync("20180401162245+08:00#d28a0288-18ab-49ce-964d-ccdca8738fc9");
// IsBusy = !IsBusy;
//});
ReadPersonEqualCommand = new Command(async() =>
{
IsBusy = true;
var readResult = await Helpers.AwsDynamoDbHelper.Instance().ReadItemEqualAsync("Name", UserNameToRetrieveText);
IsBusy = !IsBusy;
if (readResult.Count >= 1)
{
readResult.ForEach((Item itemResult) =>
{
_idText = itemResult.Id;
_timeStampText = itemResult.SavedTimeStamp;
_userNameText = itemResult.Name;
_userEmailText = itemResult.Email;
_userPasswordText = itemResult.Password;
});
//****** Adapted from https://forums.xamarin.com/discussion/comment/280634/#Comment_280634 (taken from NMackay's June 2017 answer in https://forums.xamarin.com/discussion/97734/how-to-update-label-in-asynctask-from-the-viewmodel).
IdText = _idText;
TimeStampText = _timeStampText;
UserNameText = _userNameText;
UserEmailText = _userEmailText;
UserPasswordText = _userPasswordText;
//******
}
else
{
IdText = "No result found";
TimeStampText = "No result found";
UserNameText = "No result found";
UserEmailText = "No result found";
UserPasswordText = "No result found";
}
RetrievedItemDataStore.Instance().retrievedName = UserNameToRetrieveText; //Is it necessary to store the UserNameToRetrieveText?
RetrievedItemDataStore.Instance().id = IdText;
RetrievedItemDataStore.Instance().savedTimeStamp = TimeStampText;
RetrievedItemDataStore.Instance().name = UserNameText;
RetrievedItemDataStore.Instance().email = UserEmailText;
RetrievedItemDataStore.Instance().password = UserPasswordText;
//System.Diagnostics.Debug.WriteLine("Name = " + _userNameText + ", Email = " + _userEmailText + ", Password = "******"Name = " + UserNameText + ", Email = " + UserEmailText + ", Password = " + UserPasswordText);
});
}
//******
//****** Adapted from the Query and Scan section in https://docs.aws.amazon.com/mobile/sdkforxamarin/developerguide/dynamodb-integration-objectpersistencemodel.html
/// <summary>
/// Reads items where the contents of the field is equal to the query string. This method is async.
/// </summary>
/// <returns>A List of items.</returns>
/// <param name="fieldToQuery">Field to query.</param>
/// <param name="queryString">Query string.</param>
public async Task <List <Item> > ReadItemEqualAsync(string fieldToQuery, string queryString)
{
if (string.IsNullOrEmpty(queryString))
{
List <Item> blankResponse = new List <Item>
{
new Item
{
Id = "Nothing to retrieve",
SavedTimeStamp = "Nothing to retrieve",
Name = "Nothing to retrieve",
Email = "Nothing to retrieve",
Password = "******"
}
};
RetrievedItemDataStore.Instance().retrievedName = "Nothing to retrieve"; //Is it necessary to store the UserNameToRetrieveText?
RetrievedItemDataStore.Instance().id = "Nothing to retrieve";
RetrievedItemDataStore.Instance().savedTimeStamp = "Nothing to retrieve";
RetrievedItemDataStore.Instance().name = "Nothing to retrieve";
RetrievedItemDataStore.Instance().email = "Nothing to retrieve";
RetrievedItemDataStore.Instance().password = "******";
return(blankResponse); //An error of "value cannot be null" will be thrown in the viewmodel if the queryString is null.
//So FromQueryAsync() isn't executed if queryString is null.
}
//var client = new AmazonDynamoDBClient(_credentials, RegionEndpoint.USEast2);
//DynamoDBContext context = new DynamoDBContext(client);
//QueryFilter queryFilter = null;
//switch (queryOperator)
//{
// case "Equal":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.Equal, queryString);
// break;
// case "GreaterThan":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.GreaterThan, queryString);
// break;
// case "GreaterThanOrEqual":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.GreaterThanOrEqual, queryString);
// break;
// case "LessThan":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.LessThan, queryString);
// break;
// case "LessThanOrEqual":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.LessThanOrEqual, queryString);
// break;
// case "BeginsWith":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.BeginsWith, queryString);
// break;
// case "Between":
// queryFilter = new QueryFilter(fieldToQuery, QueryOperator.Between, queryString);
// break;
//}
var search = _context.FromQueryAsync <Item>(new QueryOperationConfig()
{
//IndexName = "Name-index", //Taken from the DynamoDB dashboard when creating the Global Secondary Index.
//Filter = new QueryFilter("Name", QueryOperator.Equal, "AwsDynamoDbTest app started")
IndexName = fieldToQuery + "-index", //Taken from the DynamoDB dashboard when creating the Global Secondary Index.
Filter = new QueryFilter(fieldToQuery, QueryOperator.Equal, queryString)
});
#if DEBUG
//System.Diagnostics.Debug.WriteLine("QueryAsync() items retrieved:");
int count = 0;
var searchResponse = await search.GetRemainingAsync();
string itemData = null;
searchResponse.ForEach((item) =>
{
count++;
//System.Diagnostics.Debug.WriteLine(count + ". " + "Name = " + item.Name + ", Password = "******", Id = " + item.Id + ", SavedTimeStamp = " + item.SavedTimeStamp);
itemData += count + ". " + "Name = " + item.Name + ", Password = "******", Id = " + item.Id + ", SavedTimeStamp = " + item.SavedTimeStamp + "\n";
});
System.Diagnostics.Debug.WriteLine("ReadItemEqualAsync() retrieved " + count + " items:\n" + itemData);
count = 0;
#endif
return(searchResponse);
}