Question

我有一个包含Lat和Long信息的SQL DB。我找到了我当前的位置，并且能够从当前位置获取每个位置的距离。我可以让我的tableview显示这个距离，但是知道我想对那个tableview进行排序，以便最先列出最近的。

我的想法是我需要添加到我的SQL DB数据的距离，对某些方法进行排序，然后将该信息显示回tableview。

我的想法是我会在TableView中完成所有这些操作。寻找有关如何执行此操作的指导，以及我是否应该在tableview中执行此操作。

#import "TulsaMasterViewController.h"
#import "TulsaDetailViewController.h"
#import "Bars.h"
#import "BarDatabase.h"

@implementation TulsaMasterViewController

@synthesize barArray = _barArray;
@synthesize currentLat = _currentLat;


- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
currentLat = newLocation;

if (newLocation.horizontalAccuracy <= 100.0f) {
    [lm stopUpdatingLocation];
}

[self.tableView reloadData];
}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
NSString *msg = [[NSString alloc]initWithString:@"Error obtaining location"];
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Error" message:msg delegate:nil cancelButtonTitle:@"Done" otherButtonTitles:nil];
[alert show];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [self.barArray 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];
}

//Get the object from the array.
Bars *barObj = [self.barInfo objectAtIndex:indexPath.row];

//Set the name.
cell.textLabel.text = barObj.barName;

if (currentLat == nil) {
    cell.detailTextLabel.text = [NSString stringWithFormat:@"?"];
}else
{
    cell.detailTextLabel.text = [NSString stringWithFormat:@"%.02f", cachedDist];
}

// Set up the cell
return cell;
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([[segue identifier] isEqualToString:@"ShowDetails"]) {
    TulsaDetailViewController *detailViewController = [segue destinationViewController];

    detailViewController.detailItem = [self.barArray objectAtIndex:[self.tableView indexPathForSelectedRow].row];
}
}

- (void)viewDidLoad
{
[super viewDidLoad];

self.barArray = [BarDatabase database].barInfo;

lm = [[CLLocationManager alloc] init];
lm.delegate = self;
[lm startUpdatingLocation];
}

- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];

for (Bars *barObj in barArray) {
    NSString *strLat = barObj.Lat;
    NSString *strLong = barObj.Long;
    CLLocation *barLocation = [[CLLocation alloc] initWithLatitude:[strLat doubleValue] longitude:[strLong doubleValue]];
    CLLocationDistance distance = [currentLat distanceFromLocation:barLocation]/1000;

    [barArray addObject:[NSNumber numberWithDouble:distance]];
    NSSortDescriptor *sort=[NSSortDescriptor sortDescriptorWithKey:@"cachedDist" ascending:YES];
    [barArray sortUsingDescriptors:[NSArray arrayWithObject:sort]];
}

参考我的其余代码

Bars.h

#import <Foundation/Foundation.h>

@interface Bars : NSObject {
    NSString *barName;
    NSString *barAddress;
    NSString *Lat;
    NSString *Long;
    NSString *cachedDist;
}

@property (nonatomic, copy) NSString *barName;
@property (nonatomic, copy) NSString *barAddress;
@property (nonatomic, copy) NSString *Lat;
@property (nonatomic, copy) NSString *Long;
@property (nonatomic, copy) NSString *cachedDist;

- (id)initWithName:(NSString *)name address:(NSString *)address latitude:(NSString *)latitude longitude:(NSString *)longitude distance:(NSString *)distance;

@end

Bars.m

#import "Bars.h"

@implementation Bars

@synthesize barName = _barName;
@synthesize barAddress = _barAddress;
@synthesize Lat = _Lat;
@synthesize Long = _Long;
@synthesize cachedDist = _cachedDist;

- (id)initWithName:(NSString *)name address:(NSString *)address latitude:(NSString *)latitude longitude:(NSString *)longitude distance:(NSString *)distance;
{
if ((self = [super init])) {
    self.barName = name;
    self.barAddress = address;
    self.Lat = latitude;
    self.Long = longitude;
    self.cachedDist = distance;
}
return self;
}

@end

BarDatabase.h

#import <Foundation/Foundation.h>
#import <sqlite3.h>

@interface BarDatabase : NSObject
{
    sqlite3 *_database;
}

+ (BarDatabase *)database;
- (NSMutableArray *)barInfo;

@end

BarDatabase.m

#import "BarDatabase.h"
#import "Bars.h"

@implementation BarDatabase

static BarDatabase *_database;

+ (BarDatabase *)database {
if (_database == nil) {
    _database = [[BarDatabase alloc] init];
}
return _database;
}

- (id)init {
if ((self = [super init])) {
    NSString *sqLiteDb = [[NSBundle mainBundle] pathForResource:@"TulsaBars" 
                                                         ofType:@"sqlite"];

    if (sqlite3_open([sqLiteDb UTF8String], &_database) != SQLITE_OK) {
        NSLog(@"Failed to open database!");
    }
}
return self;
}

- (void)dealloc {
sqlite3_close(_database);
}

- (NSMutableArray *)barInfo {

NSMutableArray *retval = [[NSMutableArray alloc] init];
NSString *query = @"SELECT * FROM TulsaBars";
sqlite3_stmt *statement;
if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &statement, nil) 
    == SQLITE_OK) {
    while (sqlite3_step(statement) == SQLITE_ROW) {
        char *nameChars = (char *) sqlite3_column_text(statement, 1);
        char *addressChars = (char *) sqlite3_column_text(statement, 2);
        char *latChars = (char *) sqlite3_column_text(statement, 8);
        char *longChars = (char *) sqlite3_column_text(statement, 9);
        NSString *name = [[NSString alloc] initWithUTF8String:nameChars];
        NSString *address = [[NSString alloc] initWithUTF8String:addressChars];
        NSString *latitude = [[NSString alloc] initWithUTF8String:latChars];
        NSString *longitude = [[NSString alloc] initWithUTF8String:longChars];

        Bars *info = [[Bars alloc]
                      initWithName:name address:address latitude:latitude longitude:longitude];                        
        [retval addObject:info];
    }
    sqlite3_finalize(statement);
}
return retval;

}
@end

Answer 1

槽糕。在cellForRowAtIndexPath中不应该发生排序。这在游戏中为时已晚。如果每个单元格都是1 bar，并且条形应按距离排序，我建议您在self.barInfo的懒惰getter中进行排序（如果这是你的条形列表）。

我不确定你的模型是什么样的，但是如果每个bar对象都有一个与你的参考点无关的属性，那么你的排序看起来就像你在那里那样。

这种排序只会在加载第一个单元格（即“懒惰”部分）然后进行缓存时发生。所以你的cellForRowAtIndexPath：只需要在它的indexPath行上询问模型对象，相信它的顺序是正确的。

我不确定你熟悉这个术语有多少，所以请随意提出澄清问题，我会重复答案。

分享更多代码后编辑：我想你应该添加一个@property到名为像cachedDistance酒吧，每当你来到屏幕（viewWillAppear中），遍历酒吧并设置其缓存的距离（使用类似的代码，你有什么cellForRow ...）。然后为self.barArray实现一个getter：-(NSArray *)barArray实际上返回barArray，它使用sortDescriptor排序，并将缓存的distance属性的名称作为键。这将简化你的cellForRow ...代码。

然后，您可以扩展逻辑，以便在获得位置更新时重新计算距离，可能仅在距离之前有一定距离时才会重新计算距离。

按当前位置的距离对TableView进行排序

1 个答案: