我在使用xcode for iOS工作的代码时遇到了一个非常烦人的问题，这让我发疯了！
这将需要大量代码解释，因为我需要包含大量代码。
我有viewcontroller工作，连接到在线mysql数据库，并填充tableview。这一切都很有效。
然后我不得不复制这段代码，因为我想从另一个数据库下载并使用来自另一个mysql数据库的坐标填充mapview。
Screen5ViewController.h / Screen5ViewController.m是viewcontroller tableview的文件。
ShopTable.h / ShopTable.m是处理从数据库下载数据的代码。
这一切都有效。
Screen2ViewController.h / Screen2ViewController.m / MapTable.h / MapTable.m是我从其他数据库下载的文件，用于填充mapview。
这根本不起作用，甚至没有调用方法("NSLog(@"map table called...");") - 所以它甚至都没有尝试下载数据。
我不明白为什么这个方法甚至不被称为？
代码编译并运行时没有错误，也没有警告。
任何人都可以给予任何帮助将非常感激。我花了很多时间查看这段代码，并尝试了我能想到的一切！
Screen5ViewController.h
#import <UIKit/UIKit.h>
#import "ShopTable.h"
@interface Screen5ViewController : UIViewController <UITableViewDataSource, UITableViewDelegate, ShopTableProtocol> {
}
@property (weak, nonatomic) IBOutlet UITableView *shopTableView;
@end
Screen5ViewController.m
#import "Screen5ViewController.h"
@interface Screen5ViewController () {
ShopTable *_shopTable;
NSArray *_feedItems;
}
@end
@implementation Screen5ViewController
@synthesize
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"Screen 5";
// Set this view controller object as the delegate and data source for the table view
self.shopTableView.delegate = self;
self.shopTableView.dataSource = self;
// Create array object and assign it to _feedItems variable
_feedItems = [[NSArray alloc] init];
// Create new ShopTable object and assign it to _shopTable variable
_shopTable = [[ShopTable alloc] init];
// Set this view controller object as the delegate for the home model object
_shopTable.delegate = self;
// Call the download items method of the home model object
[_shopTable downloadItems2];
}
-(void)itemsDownloaded2:(NSArray *)items {
// This delegate method will get called when the items are finished downloading
// Set the downloaded items to the array
_feedItems = items;
// Reload the table view
[self.shopTableView reloadData];
}
#pragma mark Table View Delegate Methods
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of feed items (initially 0)
return _feedItems.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// Retrieve cell
NSString *cellIdentifier = @"shopTableCell";
UITableViewCell *myCell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
// Get the location to be shown
Location2 *item = _feedItems[indexPath.row];
// Get references to labels of cell
myCell.textLabel.text = item.name;
myCell.detailTextLabel.text = item.address;
return myCell;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
@end
ShopTable.h
#import <Foundation/Foundation.h>
@protocol ShopTableProtocol <NSObject>
- (void)itemsDownloaded2:(NSArray *)items;
@end
@interface ShopTable : NSObject <NSURLConnectionDataDelegate>
@property (nonatomic, weak) id<ShopTableProtocol> delegate;
- (void)downloadItems2;
@end
@interface Location2 : NSObject
@property (nonatomic, strong) NSString *latitude;
@property (nonatomic, strong) NSString *longitude;
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSString *address;
@end
ShopTable.m
#import "ShopTable.h"
@interface ShopTable() {
NSMutableData *_downloadedData;
}
@end
@implementation ShopTable
- (void)downloadItems2 {
NSLog(@"shop table called...");
// Download the json file
NSURL *jsonFileUrl = [NSURL URLWithString:@"http://www.example.com/shop.php"];
// Create the request
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:jsonFileUrl];
// Create the NSURLConnection
[NSURLConnection connectionWithRequest:urlRequest delegate:self];
}
#pragma mark NSURLConnectionDataProtocol Methods
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
// Initialize the data object
_downloadedData = [[NSMutableData alloc] init];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append the newly downloaded data
[_downloadedData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// Create an array to store the locations
NSMutableArray *_locations = [[NSMutableArray alloc] init];
// Parse the JSON that came in
NSError *error;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:_downloadedData options:NSJSONReadingAllowFragments error:&error];
// Loop through Json objects, create question objects and add them to our questions array
for (int i = 0; i < jsonArray.count; i++) {
NSDictionary *jsonElement = jsonArray[i];
// Create a new location object and set its props to JsonElement properties
Location2 *newLocation = [[Location2 alloc] init];
newLocation.name = jsonElement[@"title"];
newLocation.address = jsonElement[@"description"];
newLocation.latitude = jsonElement[@"Latitude"];
newLocation.longitude = jsonElement[@"Longitude"];
// Add this question to the locations array
[_locations addObject:newLocation];
}
// Ready to notify delegate that data is ready and pass back items
if (self.delegate) {
[self.delegate itemsDownloaded2:_locations];
}
}
@end
@implementation Location2
@end
Screen2ViewController.h
#import <UIKit/UIKit.h>
#import "MapTable.h"
@interface Screen2ViewController : UIViewController <MapTableProtocol> {
}
@end
Screen2ViewController.m
#import "Screen2ViewController.h"
@interface Screen2ViewController () {
MapTable *_mapTable;
NSArray *_feedItems1;
}
@end
@implementation Screen2ViewController
@synthesize
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"Screen 2";
NSLog(@"1"); // This is called fine!
// Create array object and assign it to _feedItems variable
_feedItems1 = [[NSArray alloc] init];
NSLog(@"2"); // This is called fine!
// Set this view controller object as the delegate for the home model object
_mapTable.delegate = self;
NSLog(@"3"); // This is called fine!
// Call the download items method of the home model object
[_mapTable downloadItems];
}
NSLog(@"4"); // This is called fine!
-(void)itemsDownloaded:(NSArray *)items {
// This delegate method will get called when the items are finished downloading
// Set the downloaded items to the array
_feedItems1 = items;
NSLog(@"%lu locations downloaded ok!", (unsigned long)_feedItems1.count);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
@end
MapTable.h
#import <Foundation/Foundation.h>
@protocol MapTableProtocol <NSObject>
- (void)itemsDownloaded:(NSArray *)items;
@end
@interface MapTable : NSObject <NSURLConnectionDataDelegate>
@property (nonatomic, weak) id<MapTableProtocol> delegate;
- (void)downloadItems;
@end
@interface Location : NSObject
@property (nonatomic, strong) NSString *latitude;
@property (nonatomic, strong) NSString *longitude;
@property (nonatomic, strong) NSString *name;
@end
MapTable.m
#import "MapTable.h"
@interface MapTable() {
NSMutableData *_downloadedData1;
}
@end
@implementation MapTable
- (void)downloadItems {
NSLog(@"map table called..."); // THIS CODE NEVER GETS CALLED??!!
// Download the json file
NSURL *jsonFileUrl = [NSURL URLWithString:@"http://www.example.com/map.php"];
// Create the request
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:jsonFileUrl];
// Create the NSURLConnection
[NSURLConnection connectionWithRequest:urlRequest delegate:self];
}
#pragma mark NSURLConnectionDataProtocol Methods
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
// Initialize the data object
_downloadedData1 = [[NSMutableData alloc] init];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append the newly downloaded data
[_downloadedData1 appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// Create an array to store the locations
NSMutableArray *_locations = [[NSMutableArray alloc] init];
// Parse the JSON that came in
NSError *error;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:_downloadedData1 options:NSJSONReadingAllowFragments error:&error];
// Loop through Json objects, create question objects and add them to our questions array
for (int i = 0; i < jsonArray.count; i++) {
NSDictionary *jsonElement = jsonArray[i];
// Create a new location object and set its props to JsonElement properties
Location *newLocation = [[Location alloc] init];
newLocation.name = jsonElement[@"firstname"];
newLocation.latitude = jsonElement[@"mylatitude"];
newLocation.longitude = jsonElement[@"mylongitude"];
// Add this question to the locations array
[_locations addObject:newLocation];
}
// Ready to notify delegate that data is ready and pass back items
if (self.delegate) {
[self.delegate itemsDownloaded:_locations];
}
}
@end
@implementation Location
@end
答案 0 :(得分：1)
在Screen2ViewController.h：
@interface Screen2ViewController : UIViewController <MKMapViewDelegate, MapTableProtocol> {
IBOutlet MKMapView *mapView;
}
@property (nonatomic, retain) IBOutlet MKMapView *mapView;
@end
您的MKMapView来自界面构建器可能与@property相关联，但Screen2ViewController.m中的任何地方都在使用mapView（实例变量从未初始化） self.mapView。
此外，与Screen5ViewController.m相比，您在MapTable Screen2ViewController方法中缺少-viewDidLoad初始化：
_mapTable = [[MapTable alloc] init];