定制UITextField的键盘为UIPickView

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {

    UIPickerView *_pickerView = [[UIPickerView alloc] init];

    [_pickerView sizeToFit];

    _pickerView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);

    _pickerView.delegate = self;

    _pickerView.dataSource = self;

    _pickerView.showsSelectionIndicator = YES;            

    textField.inputView = _pickerView;

    [_pickerView release];

    

    UIToolbar* keyboardDoneButtonView = [[UIToolbar alloc] init];

    keyboardDoneButtonView.barStyle = UIBarStyleBlack;

    keyboardDoneButtonView.translucent = YES;

    keyboardDoneButtonView.tintColor = nil;

    [keyboardDoneButtonView sizeToFit];

    UIBarButtonItem* doneButton = [[[UIBarButtonItem alloc] initWithTitle:@"确定"

                                                                    style:UIBarButtonItemStyleBordered target:self

                                                                   action:@selector(pickerDoneClicked:)] autorelease];

    [keyboardDoneButtonView setItems:[NSArray arrayWithObjects:doneButton, nil]];

    textField.inputAccessoryView = keyboardDoneButtonView;  

    [keyboardDoneButtonView release];          

    return YES;

}