iPhone UIDatePicker very slow

Question

我在modeltime上使用了一个UIDatePicker，

但是非常慢??

这里的代码:

#import "U2YAccountController.h"
@implementation U2YAccountController
@synthesize timePicker = _timePicker;
@synthesize timeLabel= _timeLabel;  
@synthesize scheduleLabel = _scheduleLabel;
- (id)init
{
self = [super init];
if (self) {
    // Set title
    self.title = @"Reminder Settings"; 

    CGRect dosageImageRect = CGRectMake(10, 30, 300, 62);
    UIImageView *dosageImage = [[UIImageView alloc] initWithFrame:dosageImageRect];
    [dosageImage setImage:[UIImage imageNamed:@"dosageReminderButton.png"]]; //image was a button, now just image change name of png!
    dosageImage.opaque = YES; // explicitly opaque for performance
    [self.view addSubview:dosageImage];
    [dosageImage release];


    UIButton *timeReminderButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [timeReminderButton setImage:[UIImage imageNamed:@"reminderTimeButton.png"] forState:UIControlStateNormal]; 
    [timeReminderButton setFrame:CGRectMake(10, 110, 300, 44)];
    [timeReminderButton addTarget:self action:@selector(timeReminderButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
    [timeReminderButton setAdjustsImageWhenHighlighted:NO];
    [self.view addSubview:timeReminderButton];

    self.timePicker = [[[UIDatePicker alloc] initWithFrame:CGRectMake(0, 415, 220, 180)]autorelease];
    self.timePicker.datePickerMode = UIDatePickerModeTime;
    [self.timePicker addTarget:self action:@selector(timePickerChanged:) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:self.timePicker];
    //[self.timePicker setHidden:YES];
    self.scheduleLabel = [[[UILabel alloc]initWithFrame:CGRectMake(22, 64, 200, 20)]autorelease];
    self.scheduleLabel.textColor = [UIColor colorWithRed:12/255.0 green:113/255.0 blue:186/255.0 alpha:1];
    self.scheduleLabel.text = @"Schedule 6 of 7 days";  //updated from web site!!
    [self.view addSubview:self.scheduleLabel];
    self.timeLabel = [[[UILabel alloc]initWithFrame:CGRectMake(213, 122, 80, 20)]autorelease];
    self.timeLabel.textColor = [UIColor colorWithRed:12/255.0 green:113/255.0 blue:186/255.0 alpha:1];
    self.timeLabel.backgroundColor = [UIColor clearColor];
    self.timeLabel.text = @"";
    [self.view addSubview:self.timeLabel];

    dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"hh:mma"];
}
return self;
}

 - (void) timeReminderButtonPressed :(id) sender {

recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewTapped:)] ;

[UIView beginAnimations:@"PickerUp" context:nil];
[UIView setAnimationDuration:0.3f];
[UIView setAnimationBeginsFromCurrentState:YES];
self.timePicker.frame = CGRectMake(0, 237, 320, 180);
[self.view addGestureRecognizer:recognizer];
[recognizer release];

}
- (void) timePickerChanged:(id) sender {

today = [sender date];

NSString *dateString = [dateFormat stringFromDate:today];
self.timeLabel.text = dateString;

}
- (void) viewTapped :(id) sender {
[UIView beginAnimations:@"PickerDown" context:nil];
[UIView setAnimationDuration:0.3f];
[UIView setAnimationBeginsFromCurrentState:YES];
self.timePicker.frame = CGRectMake(0, 415, 320, 180);
[self.view removeGestureRecognizer:recognizer];
}

- (void) dealloc {
[dateFormat release];

[_scheduleLabel release];
[_timeLabel release];
[_timePicker release];
[super dealloc];
}
@end

那么为什么我的拾取器很慢并且卡住了呢?我错过了什么??

p。我已经评论了nsDateFormatter，以确定这是否是问题，但没有变化…

非常感谢!

Answer 1

我的第一反应:

分配一个NSDateFormatter不是一个便宜的前景。在你的情况下，你使用相同的格式字符串一遍又一遍，所以你真的应该只是分配一个单一的NSDateFormatter，保存它作为一个实例变量，然后使用，当UIDatePicker行动火灾。这应该会大大加快速度。

Answer 2

除了前面的答案，你还需要补充一点，那就是你忘记提交动画了。我甚至会建议你使用animateWith…方法的UIView类，而不是beginAnimation/commitAnimation，因为它应该更快(至少苹果)。还有一个。手势识别器…为什么不在初始化时用视图创建它呢?为什么每次调用选择器时都要创建它?