I'm starting off developing an iPhone app. I need to present a drop down box for the customer to pick a value which will essentially be sent downstream to a database upon submit. I'm clearly using a UIPickerView for the drop down list, built from IB.
Once my view loads, the Drop down list is enabled, with all values showing.
Question is:
Can I only expand the drop down list once it's clicked?
Can I retract the list once the user selects a value?
I'm thinking very web-centric in terms of drop-downs, but I could have this all wrong.
Your view controller needs to implement the UIPickerViewDataSource as well as the UIPickerViewDelegate. In the XIB of the UIPickerView you need to link the File's Owner with the UIPickerView's delegate and datasource.
Like in the UITabelDataSource you need to provide the number of components (table: sections) inside [numberOfComponentsInPickerView]. Then you need to provide the number of rows for each component in [numberOfRowsInComponent]. Finally you need to provide the title for the each entry inside [titleForRow].
Now to bring everything to life you can use [didSelectRow] to load the next component if the previous one was selected.
Attention: UIPickerView has a little bug not to call [didSelectRow] when the component is filled / changed. In order to make it work more smoothly I added a "None" entry as the first entry which is a non-selection and does not cause the next component to be loaded.
This is a rudimentary code:
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return 3; // Number of Components aka Columns
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
if( component == 0 ) {
return [self.firstColumnEntries count] + 1;
} else if( component == 1 ) {
return [self.secondColumnEntries count] + 1;
} else if( component == 2 ) {
return [self.thirdColumnEntries count] + 1;
}
return 0;
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
NSLog( #"titleForRow(), component: %d, row: %d", component, row );
NSDictionary *item = nil;
if( row == 0 ) {
return #" --- ";
} else {
int correctedRow = row - 1;
if( component == 0 ) {
item = [self.firstColumnEntries objectAtIndex:correctedRow];
} else if( component == 1 ) {
item = [self.secondColumnEntries objectAtIndex:correctedRow];
} else if( component == 2 ) {
item = [self.thirdColumnEntries objectAtIndex:correctedRow];
}
return [item objectForKey:#"name"]; // My objects are NSDictionarys
}
}
- (void) pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
DLog( #"SSVC.didSelectRow(), component: %d, row: %d", component, row );
ActionRequest *action = nil;
if( row == 0 ) {
if( component == 0 ) {
[self refreshFirstColumn:self.firstColumnEntries];
} else if( component == 1 ) {
...
}
} else {
// Last Column is selected. Now selection is complete
...
}
}
Because the UIPickerView takes away a lot of space and you cannot change it size I would recommend to place it on an additional UIView (make the rest transparent) and display it when the user selected the field that is assigned to the value (UITextField). When the selection is done (either when last value is selected or when the user enter a button) you let the View disappear and set the value onto the UITextField. Make sure that the UITextField cannot be edited and that entering it make the View with the Picker View appear. When done make sure that you also move to the next field.
You have a couple options:
Probably easiest for a beginner: push a new view (either as a modal view or onto the nav stack) that presents the list either as a table view where they click the item they want or as a pickerView where it scrolls.
Review the twitter app 'my profile' view. While I haven't done this personally, I think it's simply using the didSelectRowAtIndex to determine which section the user clicked and then filling an array of values for that section before calling [tableView reloadData]
Related
I am using grouped tableview for developing a contact list using database. I have to show the message "No Contacts" on tableview when there is no contact in list. how can I do it?
Share your ideas..
Thanks in Advance
supposing that you are using an array to store all the contacts then use the following delegate
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// You can also modify this condition according to a specific section
if([YOUR_ARRAY count] == 0)
{
return 1;
}
else
return [YOUR_ARRAY count];
}
Now adding data to table in following delegate
-(UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Initialise your cell
if([YOUR_ARRAY count] > 0){
// add your array data to cells
}
if([YOUR_ARRAY count] == 0){
// this means no contacts in array and therfore you have only one cell to display NO CONTACTS
}
return cell;
}
For cases like this one we used table headers.
If the table had elements in his data source, the table header was clear and had a 1px height.
If the data source had no elements, then the table header view was set as big as the table's frame and contained a message, an image or whatever you might need.
The functions (table view delegate methods, actually) we used were height for header in section and view for header in section. We verified the data source inside the viewForHeader function
You can achieve the same effect using the table footers as well
you can add UILabel
ande set the text of the label
label.text = #"No results ";
and you make a test
if ([contacts count] == 0)
{
yourTableview.hidden = YES;
yourLabel.hidden = NO;
}
else
{
yourTableview.hidden = NO;
yourLabel.hidden = YES;
}`
I have RSS, and the UITableView loads data from it, how can I show UIAlertView if the UITableView is empty, but not by count of an array because the array is different every time it is refreshed, is there some kind of function which will check if UITableView is empty after it completes drawing?
You can query the UITableView itself. So assuming you have a single section you could do the following ...
// Reload the tableview
[tableView reloadData];
// Test the number of rows in the first section
if ([tableView numberofRowsInSection:0] == 0) {
// Display UIAlertView here
}
EDIT; Based on the comments below ...
In your header file (.h) iVar declarations ...
int feedCount;
int feedsParsed;
In your implementation ...
- (void)refresh {
feedCount = 0;
feedsParsed = 0;
[feedParser stopParsing];
self.title = #"Refreshing...";
[parsedItems removeAllObjects];
for (NSString *imePredmeta in [Data variables].mojiPredmeti) {
... // I've removed these lines for brevity but they are still required
[feedParser parse];
feedCount += 1;
}
// Delete everything else after this line
}
- (void)feedParserDidFinish:(MWFeedParser *)parser {
feedsParsed += 1;
if (feedsParsed == feedCount) {
[self.tableView reloadData];
if ([self.tableView numberofRowsInSection:0] == 0) {
// Fade out tableview and display alert here as we now know for
// sure that there are no more feeds to parse and we definitely
// have nothing to display
}
}
}
You will need to loop round the array and check to determine if there are no results.
Please post your existing tableview code if you want a more explicit answer.
edit: micpringle answer above is better.
Hai,In my app i want to place the 4 pickerviews.And i place the one segment control with 3 segments.If we click on first segment then firstpicker will be display.Likewise remaining pickers are display for remaining segments.But,only first picker will be displayed and remaining pickers are not show components and rows.Only display black screen.Please provide any help.Please urgent.
To again call the delegates, call the following line
[pickerview reloadComponent];
create outlet and make use of hidden property...means if you tap on first segment make first picker as highlighted and similarly for other segments with respective pickers...
do you want to resize ??
Edit: added code from below for formatting purposes
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return ( pickerView == picker1 ? 2 : 3 );
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { NSArray *values = ( pickerView == picker1 ? values1 : values2 );
return [values count];
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
NSArray *values = ( pickerView == picker1 ? values1 : values2 );
return [values objectAtIndex: row];
}
check like this..
I'm developing an application with a picker view that slide from the bottom (like an action sheet). I need to convert 3 units (litres, us gallons and imperial gallons). The value is taken from a text field but I don't know how to tell the compiler which was the unit to start from.
(ie...the user insert the value in the the text field but if he changes the units (usg or ig), the value in the text field changes accordingly.
this is the array:
NSMutableArray *weightArray = [[NSMutableArray alloc] initWithObjects:#"", #"Ltr",#"Usg",#"Ig",
nil];
self.weightPickerViewArray = weightArray;
[weightArray release];`
this is the picker:
- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
if (row == 1) {
labelVolume.text = [weightPickerViewArray objectAtIndex:row];
//more code here....
}else if (row == 2){
labelVolume.text = [weightPickerViewArray objectAtIndex:row];
//more code here....
}else if (row == 3){
labelVolume.text = [weightPickerViewArray objectAtIndex:row];
//more code here....
}
how can I tell the compiler which was the value before the selection?
Add a text indicating the units at the end of the string.
- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
if (row == 1) {
NSString *initalValue = labelVolume.text;
// Do your calculations here based on unit
NSString *updatedValue = urNewValue;
labelVolume.text = updatedValue;
//more code here....
}else if (row == 2){
NSString *initalValue = labelVolume.text;
// Do your calculations here based on unit
NSString *updatedValue = urNewValue;
labelVolume.text = updatedValue;
//more code here....
}else if (row == 3){
NSString *initalValue = labelVolume.text;
// Do your calculations here based on unit
NSString *updatedValue = urNewValue;
labelVolume.text = updatedValue;
//more code here....
}
When you select a row in picker, it call's its delegate method pickerView:didSelectRow:inComponent:
Here, you can can change the value of your text field depending on which row (liters, gallons, etc) user selected.
Please refer the apple's class reference for UIPickerView delegate
If I understand your problem. You want catch event when user change units in your pickerView, pass the information to the view that contains text field and execute conversion.
So you can use NSNotificationCenter (documentation here). In your pickerView when value change put this code :
[[NSNotificationCenter defaultCenter] postNotificationName:#"unitValueChange" object:#"litres"];
In the view that contains UITextField put this code :
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(myMethodToExecute:) name:#"unitValueChange" object:self];
Now when your PickerView launch notification your view launch this method :
-(void)myMethodToExecute:(NSNotification *)notif{
NSString *myUnitSelected = notif.object
}
In my project i am filling the picker view array with the value which i am getting from the service.And in the same view i have another label on click of button in the label i want to get the same uipickerview with different value is that possible.....so with one picker view my work will be done no need to call to different picker views...anyone has solution for this isssue
i dont think so .. it will only be possible if you load the data again which means the uipicker(all same instance) with loaded with same data
of course this is possible. Just switch to another model that holds the data that is used in the picker.
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
if (myCurrentEditingValue == MyCountryValue) {
return ...
}
else if (myCurrentEditingValue == MyCityValue) {
return ...
}
return nil;
}
- (IBAction)startEditingCountryField {
myCurrentEditingValue = MyCountryValue;
[picker reloadAllComponents];
}
You should get the idea.