UITableViewCell - 为选定行保留复选标记

Question

这是UITableViewCell - check mark one row per section 的后续问题。 这里我有 2 个部分，每个部分有 3 行，如下所示：

1. 搜索距离

   • 250 英尺

   • 1000 英尺

   • 4000 英尺

2. 地图类型

   • 标准

   • 卫星

   • 混合

我在第 2 部分（地图类型）中遇到问题。我希望将“标准”检查为默认值，用户稍后选择的任何选项都可以保存并传递到另一个视图控制器，该控制器包含要根据所选地图类型显示的地图视图。我当前的代码不允许我为 section2 这样做。任何人，请帮助检查我的代码并建议我需要添加/修改什么？

我一直在尝试了解第 1 节（搜索距离）的工作原理，但我只是不太明白。它似乎涉及委托文件来做缓存的事情。

我的代码是：

#import "PAWSettingsViewController.h"

#import "PAWAppDelegate.h"
#import <Parse/Parse.h>

@interface PAWSettingsViewController ()

- (NSString *)distanceLabelForCell:(NSIndexPath *)indexPath;
- (PAWLocationAccuracy)distanceForCell:(NSIndexPath *)indexPath;

- (NSString *)maptypeLabelForCell:(NSIndexPath *)indexPath;  
- (PAWMaptypeSelect)maptypeForCell:(NSIndexPath *)indexPath;

@property (nonatomic, assign) CLLocationAccuracy filterDistance;

@end

typedef enum {
    kPAWSettingsTableViewDistance = 0,
    kPAWSettingsTableViewMaptype,
    kPAWSettingsTableViewNumberOfSections
} kPAWSettingsTableViewSections;

typedef enum {
    kPAWSettingsTableViewDistanceSection250FeetRow = 0,
    kPAWSettingsTableViewDistanceSection1000FeetRow,
    kPAWSettingsTableViewDistanceSection4000FeetRow,
    kPAWSettingsTableViewDistanceNumberOfRows
} kPAWSettingsTableViewDistanceSectionRows;

typedef enum {
    kPAWSettingsTableViewMaptypeSectionStandardRow = 0,
    kPAWSettingsTableViewMaptypeSectionSatelliteRow,
    kPAWSettingsTableViewMaptypeSectionHybridRow,
    kPAWSettingsTableViewMaptypeNumberOfRows
} kPAWSettingsTableViewMaptypeSectionRows;

@implementation PAWSettingsViewController

@synthesize tableView;
@synthesize filterDistance;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        PAWAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        self.filterDistance = appDelegate.filterDistance;
    }
    return self;
}

#pragma mark - Custom setters

// Always fault our filter distance through to the app delegate. We just cache it locally because it's used in the tableview's cells.
- (void)setFilterDistance:(CLLocationAccuracy)aFilterDistance {
    PAWAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    appDelegate.filterDistance = aFilterDistance;
    filterDistance = aFilterDistance;
}

#pragma mark - View lifecycle

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Private helper methods

- (NSString *)distanceLabelForCell:(NSIndexPath *)indexPath {
    NSString *cellText = nil;
    switch (indexPath.row) {
        case kPAWSettingsTableViewDistanceSection250FeetRow:
            cellText = @"250 feet";
            break;
        case kPAWSettingsTableViewDistanceSection1000FeetRow:
            cellText = @"1000 feet";
            break;
        case kPAWSettingsTableViewDistanceSection4000FeetRow:
            cellText = @"4000 feet";
            break;
        case kPAWSettingsTableViewDistanceNumberOfRows: // never reached.
        default:
            cellText = @"The universe";
            break;
    }
    return cellText;
}

- (PAWLocationAccuracy)distanceForCell:(NSIndexPath *)indexPath {
    PAWLocationAccuracy distance = 0.0;
    switch (indexPath.row) {
        case kPAWSettingsTableViewDistanceSection250FeetRow:
            distance = 250;
            break;
        case kPAWSettingsTableViewDistanceSection1000FeetRow:
            distance = 1000;
            break;
        case kPAWSettingsTableViewDistanceSection4000FeetRow:
            distance = 4000;
            break;
        case kPAWSettingsTableViewDistanceNumberOfRows: // never reached.
        default:
            distance = 10000 * kPAWFeetToMiles;
            break;
    }
    return distance;
}

- (NSString *)maptypeLabelForCell:(NSIndexPath *)indexPath {
    NSString *cellText = nil;
    switch (indexPath.row) {
        case kPAWSettingsTableViewMaptypeSectionStandardRow:
            cellText = @"Standard";
            break;
        case kPAWSettingsTableViewMaptypeSectionSatelliteRow:
            cellText = @"Satellite";
            break;
        case kPAWSettingsTableViewMaptypeSectionHybridRow:
            cellText = @"Hybrid";
            break;
        case kPAWSettingsTableViewMaptypeNumberOfRows: // never reached.
        default:
            cellText = @"?";
            break;
    }
    return cellText;
}

- (PAWMaptypeSelect)maptypeForCell:(NSIndexPath *)indexPath {
    PAWMaptypeSelect maptype = nil;
    switch (indexPath.row) {
        case kPAWSettingsTableViewMaptypeSectionStandardRow:
            maptype = @"Standard";
            break;
        case kPAWSettingsTableViewMaptypeSectionSatelliteRow:
            maptype = @"Satellite";
            break;
        case kPAWSettingsTableViewMaptypeSectionHybridRow:
            maptype = @"Hybrid";
            break;
        case kPAWSettingsTableViewMaptypeNumberOfRows: // never reached.
        default:
            maptype = nil;
            break;
    }
    return maptype;
}

#pragma mark - UINavigationBar-based actions

- (IBAction)done:(id)sender {
    [self.presentingViewController dismissModalViewControllerAnimated:YES];
}

#pragma mark - UITableViewDataSource methods

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return kPAWSettingsTableViewNumberOfSections;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    switch ((kPAWSettingsTableViewSections)section) {
        case kPAWSettingsTableViewDistance:
            return kPAWSettingsTableViewDistanceNumberOfRows;
            break;
        case kPAWSettingsTableViewMaptype:
            return kPAWSettingsTableViewMaptypeNumberOfRows;
            break;
        case kPAWSettingsTableViewNumberOfSections:
            return 0;
            break;
    };
}

- (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *identifier = @"SettingsTableView";
    if (indexPath.section == kPAWSettingsTableViewDistance) {
        UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:identifier];
        if ( cell == nil )
        {
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:identifier];
        }

        // Configure the cell.
        cell.tag = indexPath.section;
        cell.textLabel.text = [self distanceLabelForCell:indexPath];

        if (self.filterDistance == 0.0) {
            NSLog(@"We have a zero filter distance!");
        }

        PAWLocationAccuracy filterDistanceInFeet = self.filterDistance * ( 1 / kPAWFeetToMeters);
        PAWLocationAccuracy distanceForCell = [self distanceForCell:indexPath];
        if (abs(distanceForCell - filterDistanceInFeet) < 0.001 ) {
            cell.accessoryType = UITableViewCellAccessoryCheckmark;
        } else {
            cell.accessoryType = UITableViewCellAccessoryNone;
        }

        return cell;
    } else if (indexPath.section == kPAWSettingsTableViewMaptype){
        UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:identifier];
        if ( cell == nil )
        {
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:identifier];
        }

        // Configure the cell.
        cell.tag = indexPath.section;
        cell.textLabel.text = [self maptypeLabelForCell:indexPath];
        //**** I don't know how to do here? ****
        return cell;
    } else {
        return nil;
    }
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    switch ((kPAWSettingsTableViewSections)section) {
        case kPAWSettingsTableViewDistance:
            return @"Search Distance";
            break;
        case kPAWSettingsTableViewMaptype:
            return @"Map Type";
            break;
        case kPAWSettingsTableViewNumberOfSections:
            return @"";
            break;
    }
}

#pragma mark - UITableViewDelegate methods

// Called after the user changes the selection.
- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == kPAWSettingsTableViewDistance) {
        [aTableView deselectRowAtIndexPath:indexPath animated:YES];

        // if we were already selected, bail and save some work.

        UITableViewCell *selectedCell = [aTableView cellForRowAtIndexPath:indexPath];
        if (selectedCell.accessoryType == UITableViewCellAccessoryCheckmark) {
            return;
        }

        // uncheck all visible cells.

        for (UITableViewCell *cell in [aTableView visibleCells]) {
            if (cell.accessoryType != UITableViewCellAccessoryNone && cell.tag == indexPath.section) {
                cell.accessoryType = UITableViewCellAccessoryNone;
            }
        }
        selectedCell.accessoryType = UITableViewCellAccessoryCheckmark;

        PAWLocationAccuracy distanceForCellInFeet = [self distanceForCell:indexPath];
        self.filterDistance = distanceForCellInFeet * kPAWFeetToMeters;
    }
    else if (indexPath.section == kPAWSettingsTableViewMaptype){
        [aTableView deselectRowAtIndexPath:indexPath animated:YES];

        // if we were already selected, bail and save some work.

        UITableViewCell *selectedCell = [aTableView cellForRowAtIndexPath:indexPath];
        if (selectedCell.accessoryType == UITableViewCellAccessoryCheckmark) {
            return;
        }

        // uncheck all visible cells.

        for (UITableViewCell *cell in [aTableView visibleCells]) {
            if (cell.accessoryType != UITableViewCellAccessoryNone && cell.tag == indexPath.section) {
                cell.accessoryType = UITableViewCellAccessoryNone;
            }
        }

        selectedCell.accessoryType = UITableViewCellAccessoryCheckmark;

        //**** I don't know how to do here? ****
    }

}

@end

Answer 1

使用布尔变量。比如 isFirstTime。

然后在 viewDidLoad: 中初始化你的 isFirstTime 变量为 YES。

isFirstTime = YES;

在你的

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

更新这部分

else if (indexPath.section == kPAWSettingsTableViewMaptype){
    UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:identifier];
    if ( cell == nil )
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:identifier];
    }
    if ( isFirstTime == YES && indexPath.row == 0)
    {

    }        // Configure the cell.
    cell.tag = indexPath.section;
    cell.textLabel.text = [self maptypeLabelForCell:indexPath];
    //**** I don't know how to do here? ****
    return cell;
}

Answer 2

我想出了自己的问题。我决定使用全局变量来保存第 2 节中的选择。 我在 .m 文件中声明了全局变量：

int gmaptypeSelected;

在 cellForRowAtOIndexPath 部分我提出了这样的条件：

else if (indexPath.section == kPAWSettingsTableViewMaptype){
        UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:identifier];
        if ( cell == nil )
        {
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:identifier];
        }


    // Configure the cell.
    cell.tag = indexPath.section;
    cell.textLabel.text = [self maptypeLabelForCell:indexPath];

    MKMapType maptypeForCell = [self maptypeForCell:indexPath];
    if (maptypeForCell == gmaptypeSelected) {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    } else {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }

    return cell;
}

在 MapView Controller > viewWillAppear 将如下所示：

- (void)viewWillAppear:(BOOL)animated {

    extern int gmaptypeSelected;
    if (gmaptypeSelected == 0) {
        self.mapView.mapType = MKMapTypeStandard;
    } else if (gmaptypeSelected == 1) {
        self.mapView.mapType = MKMapTypeSatellite;
    } else if (gmaptypeSelected == 2) {
        self.mapView.mapType = MKMapTypeHybrid;
    }

    [locationManager startUpdatingLocation];
    [super viewWillAppear:animated];
}