Question

I have Xcode 4.2 and I am trying to create a drop down menu. I would like the drop down menu to drop down with words or numbers. Then when I select something from the list I would like it to appear in a table on a different page. My question is: how would I write this?
Thanks

Answer 1

First create a UIViewController subclass with a nib file by going File > New > New File and following the prompts.

Now open the nib (MyViewController.xib).

You should drag a UIPickerView and a UITableView into the view and arrange them however you like (it doesn’t matter).

Next open the header file (MyViewController.h) for your UIViewController subclass.

At the end of the

@interface MyViewController : UIViewController {

line add <UITableViewDelegate, UITableViewDataSource, UIPickerViewDelegate, UIPickerViewDataSource> so it looks like this

@interface MyViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, UIPickerViewDelegate, UIPickerViewDataSource>

Next you will need to add references to your tableview and picker and also two arrays of values. Just above @end add the following lines

@property (strong, nonatomic) IBOutlet UITableView* tableView;
@property (strong, nonatomic) IBOutlet UIPickerView* pickerView;
@property (strong, nonatomic) NSMutableArray* tableData;
@property (strong, nonatomic) NSMutableArray* pickerData;

Then just go back to your nib file and connect the UITableView and UIPickerView to these variables.

Now in your source file (MyViewController.m) you need to synthesize you references. So add @synthesize tableView, pickerView, tableData, pickerData to the file just below @implementation MyViewController

Now to add the delegate methods, there will be quite a few of them, but they’re pretty self explanatory.

The delegate methods for the UITableView are

- (NSInteger)numberOfSectionsInTableView:(UITableView*)tableView;

- (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section;

- (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;

- (void)tableView:(UITableView*)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;

The delegate methods for the UIPickerView are

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView;

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component;

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component;

They should be added to the source file and used as follows

UITableView:

- (NSInteger)numberOfSectionsInTableView:(UITableView*)tableView {
    // The number of sections in the UITableView
    return 1;
}

- (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section {
    // The number of rows in the UITableView
    return [tableData count];
}

- (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    }

    // Set the table cell text to the appropriate value in tableData
    cell.textLabel.text = [tableData objectAtIndex:indexPath.row];

    return cell;
}

- (void)tableView:(UITableView*)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // Whatever happens when you select a table view row.
}

UIPickerView:

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView;
{
    // The number of sections in the UIPickerView
    return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;
{
    // The number of rows in the UIPickerView
    return [pickerData count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component;
{
    // The data for each row in the UIPickerView
    return [pickerData objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    // whatever you want to happen when a row is selected.

    // here I am assuming you want to remove from the picker and add to the table on selection
    [tableData addObject:[pickerData objectAtIndex:row]];
    [pickerData removeObjectAtIndex:row];

    [tableView reloadData];
    [pickerView reloadAllComponents];
}

Ok, the final thing you have to do is set the delegates and initialise the data. In the - (void)viewDidLoad method of MyViewController add the following lines

tableView.delegate = self;
tableView.dataSource = self;
pickerView.delegate = self;
pickerView.dataSource = self;

tableData = [[NSMutableArray alloc] init]; // table starts empty
pickerData = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3", @"4", @"5", nil]; // picker starts with values 1, 2, 3, 4, 5

[tableView reloadData];
[pickerView reloadAllComponents];

There are a few more delegate methods which you can find in the spec for the classes but these ones should be adequate for now.