Question

我正在尝试将Annotations添加到数组中以在地图上放置多个引脚。我把所有东西都放在for循环中。它第一次循环，它将对象添加到数组就好了。当它返回...时，数组中有0个对象。谁能告诉我为什么？

编辑：我正在使用ARC。

-(void)plotMultipleLocs {
float latitude;
float longitude;
NSRange commaIndex;
NSString *coordGroups;
for (int i=0; i<=cgIdArray.count; i++) {
    coordGroups = [cgInAreaArray objectAtIndex:i];
    commaIndex = [coordGroups rangeOfString:@","];
    latitude = [[coordGroups substringToIndex:commaIndex.location] floatValue];
    longitude = [[coordGroups substringFromIndex:commaIndex.location + 1] floatValue];
    CLLocationCoordinate2D loc = CLLocationCoordinate2DMake(latitude, longitude);
    MKCoordinateRegion reg = MKCoordinateRegionMakeWithDistance(loc, 1000, 1000);
    self->mapView.region = reg;
    MKPointAnnotation* ann = [[MKPointAnnotation alloc] init];
    ann.coordinate = loc;
    ann.title = [cgNameArray objectAtIndex:i];
    ann.subtitle = [cgLocArray objectAtIndex:i];
    NSMutableArray *mutAnnArray = [NSMutableArray arrayWithArray:annArray];
    [mutAnnArray addObject:ann];
 }
}

Answer 1

您正在循环中创建一个可变数组并将对象添加到其中。

在循环的下一次迭代中，您将创建一个新的可变数组并为其添加新注释。

不考虑您是从另一个数组创建它而不是仅仅将注释添加到annArray

基本上，您添加对象的数组只要进行一次迭代，然后超出范围。

尝试将数组移出循环：

-(void)plotMultipleLocs {
    float latitude;
    float longitude;
    NSRange commaIndex;
    NSString *coordGroups;

    NSMutableArray *mutAnnArray = [NSMutableArray arrayWithArray:annArray]; // Create one array outside the loop.

    for (int i=0; i<=cgIdArray.count; i++) {
        coordGroups = [cgInAreaArray objectAtIndex:i];
        commaIndex = [coordGroups rangeOfString:@","];
        latitude = [[coordGroups substringToIndex:commaIndex.location] floatValue];
        longitude = [[coordGroups substringFromIndex:commaIndex.location + 1] floatValue];
        CLLocationCoordinate2D loc = CLLocationCoordinate2DMake(latitude, longitude);
         MKCoordinateRegion reg = MKCoordinateRegionMakeWithDistance(loc, 1000, 1000);
         self->mapView.region = reg;
         MKPointAnnotation* ann = [[MKPointAnnotation alloc] init];
         ann.coordinate = loc;
         ann.title = [cgNameArray objectAtIndex:i];
         ann.subtitle = [cgLocArray objectAtIndex:i];
        [mutAnnArray addObject:ann]; // Add the annotation to the single array.
    }

// mutAnnArray will go out of scope here, so maybe return it, or assign it to a property
}

Answer 2

您是否尝试过保留实例以避免被释放？

Answer 3

每次循环时，都会创建一个包含不同数组内容的新可变数组。包含您在上一次迭代中添加的对象的可变数组不会保留。

NSMutableArray似乎过早地释放了

3 个答案: