如何使UIView的內容失效以強制重繪？

Question

我有一個UIView，就像一個時間表（使用XCode 4.6，iOS 6.2和Storyboards編寫的iPad應用程序）。我實際上有兩個UIVIews，一個在窗口的上半部分，另一個在下半部分。上半部分有一個日曆;和一個低於這個時間的網格。當用戶點擊具有約會的一天時，它們將繪製在底部的UIView上。用戶可以通過預約點擊任何一天，並刪除舊的，新的數據在底部視圖上繪製。

這很有效，除非當天沒有約會被點擊，在這種情況下舊數據仍然存在，而不是被刪除。我試過[self setNeedsDisplay]，但由於沒有任何變化，所以沒有任何東西被繪製。有沒有辦法使UIView的內容無效，強制它沒有數據重繪？

UPDATE：這裏是繪製任命代碼：

- (void)drawRect:(CGRect)rect { 

// load dictionary files from plists 
NSString *path = [[NSBundle mainBundle] bundlePath]; 
// NSLog(@"\n\npath %@",path); 
// 
NSString *timesFinalPath = [path stringByAppendingPathComponent:@"startingTimes.plist"]; // do starting times 
NSDictionary *startDict = [NSDictionary dictionaryWithContentsOfFile:timesFinalPath]; 

NSString *namesFinalPath = [path stringByAppendingPathComponent:@"techNames.plist"]; // do tech names 
NSDictionary *techDict = [NSDictionary dictionaryWithContentsOfFile:namesFinalPath]; 
// NSLog(@"\nPath: %@\ntechDict.count: %d\nstartDict.count %d", path, techDict.count, startDict.count); 

// NSLog(@"nbr of recognizers: %lu", (unsigned long)self.gestureRecognizers.count); 


// find out how many appointments we have for this day 
SingletonAppointments *sharedInstance = [SingletonAppointments sharedInstance]; // initialize 

if(sharedInstance.globalApptList.count > 0) { 

    for(int i = 0; i < sharedInstance.globalApptList.count; i++) { // get customer apointments for this day 

     AppointmentInfo *apptObject = [sharedInstance.globalApptList objectAtIndex:i]; 

     //NSLog(@"apptObject.aApptKey: %@", apptObject.aApptKey); 

     // using apptObject.aApptKey, get the client's name 
     NSPredicate *predicate = ([NSPredicate predicateWithFormat:@"(aClientKey = %@)", apptObject.aApptKey]); 
     clientInfo = [ClientInfo MR_findAllWithPredicate: predicate]; 
     NSString *cliInfo; 
     for (ClientInfo *cli in clientInfo) { 
      cliInfo = cli.aClientName; // found client name 
     } 

     // settings for name drawing 
     const float nameFontSize = 14; 
     UIFont *hourfont=[UIFont systemFontOfSize: nameFontSize]; 

     // now compute the duration 
     NSDateFormatter *df = [[NSDateFormatter alloc] init]; 
     [df setDateFormat:@"HH:mm"]; 
     NSTimeInterval interval = [apptObject.aEndTime timeIntervalSinceDate:apptObject.aStartTime]; 
     int hours = (int)interval/3600;    // integer division to get the hours part 
     int minutes = (interval - (hours*3600))/60; // interval minus hours part (in seconds) divided by 60 yields minutes 
     //   NSString *duration = [NSString stringWithFormat:@"%d:%02d", hours, minutes]; 

     // localize time 
     NSDate *sTime = [self localizeDate: apptObject.aStartTime]; 
     //   NSDate *eTime = [self localizeDate: apptObject.aEndTime]; 
     //   NSLog(@"\n\nsTime: %@ eTime: %@", sTime, eTime); 
     //   NSLog(@"\nlocalized sTime: %@\nlocalized eTime %@", sTime, eTime); 

     // determine time slot (dictiionary starts at 0900... must accomodate for that) 
     NSDateFormatter *formatter = [[NSDateFormatter alloc] init]; 
     [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"GMT"]]; //Optionally for time zone converstions 
     [formatter setDateFormat:@"HH:mm"]; 

     // get time shop opens and closes 
     PreferenceData *prefDataFound = [PreferenceData MR_findFirst]; 
     if(prefDataFound) { // fill the times 
      startHour = prefDataFound.aShopOpens; 
      endHour = prefDataFound.aShopCloses; 
     } 
     //   NSLog(@"startHour: %@ endHour: %@",startHour, endHour); 

     // now, get first time slot in dictionary 
     NSArray *ts = [startDict allKeysForObject:[NSNumber numberWithInt:5]]; // comes back with one entry: 9:00 

     // clean it (remove colon) 
     NSString *dictValue = ts[0]; 
     NSString *cleanDictValue = [dictValue stringByReplacingOccurrencesOfString:@":" withString:@""]; 

     // convert to int 
     int dictStartTime = [cleanDictValue intValue]; 
     int intStartHour = [startHour intValue]; 

     // compute gridTimeOffset 
     float gridTimeOffset = dictStartTime - intStartHour; 

     NSString *stringFromDate = [formatter stringFromDate:sTime]; 
     //   NSLog(@"\n\nstringFromDate: %@",stringFromDate); 
     //   NSLog(@"\nserviceTech: %@", apptObject.aServiceTech); 

     // find the correct column by tech name 
     NSNumber *techColumn = [techDict objectForKey:apptObject.aServiceTech]; 
     //   NSLog(@"\nserviceTech: %@, techColumn: %@", apptObject.aServiceTech, techColumn); 

     // set the context 
     CGContextRef context = UIGraphicsGetCurrentContext(); 


     // draw the name... (x refers to column; y refers to time slot) 
     [[UIColor blueColor] set]; // sets color of customer name 
     NSNumber *timeSlot = [startDict objectForKey:stringFromDate]; 
     float correctedSlot = [timeSlot floatValue] + gridTimeOffset; // corrected slot info for name and rectangle 
     [cliInfo drawAtPoint:CGPointMake([techColumn floatValue], correctedSlot) withFont:hourfont]; 
     //   NSLog(@"\ntimeSlot: %@ adjusted: %@", [timeSlot floatValue], ([timeSlot floatValue] - gridTimeOffset)); 


     // make some settings for the blocking 
     UIGraphicsBeginImageContext(self.bounds.size); 
     //   CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor); 
     //   CGContextSetLineWidth(context, 1.0); 

     // get the CGContextRef for drawing the rectangle 
     CGContextSetFillColorWithColor(context, [[[UIColor grayColor] colorWithAlphaComponent: 0.3] CGColor]); 

     //   NSNumber *startPos = [startDict objectForKey:stringFromDate]; 
     int shadeHeight = ((hours * 4) + (minutes/15)) * 25; // compute starting y value 

     //   CGContextFillRect(context, CGRectMake([techColumn floatValue], [startPos floatValue], 218, (float)shadeHeight)); 
     CGContextFillRect(context, CGRectMake([techColumn floatValue], correctedSlot, 218, (float)shadeHeight)); 

     UIGraphicsEndImageContext(); // end the context so the other appointments will draw 
    } 

} 

}

Answer 1

這一點應在該視圖控制器的回調處理控制仰視圖。 （如果你有一個視圖控制器同時控制頂部和底部，同樣適用。）在其更新方法中（選擇一天時應該調用它，包括空天），應該是這樣的。

-(void)update { 
    if (selectedDay.events && selectedDay.events.count) { 
     // do your normal update 
    } 
    else { 
     // empty the view 
    } 
} 

注意，如果底視圖是或具有表視圖，重置數據陣列或集合（如上selectedDay.events引用），並調用

[_tableView reloadData]; 

如果你有一些其他方案你會必須「手動」清空它。

EDIT

作爲斯波坎-啞彈指出的那樣，有一個與數據源單一個缺陷。在適當的情況下，數據必須明確設置爲無。

if(appointmentInfo.count > 0) { 
    for (AppointmentInfo *appt in appointmentInfo) { 
     sharedInstance.globalApptList = appointmentInfo; // move data to sharedInstance 
    } 
} 
else { 
    sharedInstance.globalApptList = nil; 
}