Question

for (int i = 0; i< [delarsInfoArray count] ; i++)
{
    NSString *lattitudeValue;
    NSString *longitudeValue;
    if ([[delarsInfoArray objectAtIndex:i]count]>1) {
        lattitudeValue = [[[delarsInfoArray objectAtIndex:i]valueForKey:@"LATITUDE"]objectAtIndex:1];
        longitudeValue = [[[delarsInfoArray objectAtIndex:i]valueForKey:@"LONGITUDE"]objectAtIndex:0];
    }
    else
    {
        lattitudeValue = @"";
        longitudeValue = @"";
    }
    CLLocationCoordinate2D pinLocation;
    if(([lattitudeValue floatValue] != 0) && ([longitudeValue floatValue] != 0) ) {
        mapRegion.center.latitude = [lattitudeValue floatValue];
        mapRegion.center.longitude = [longitudeValue floatValue];
        if(pinLocation.latitude !=0 && pinLocation.longitude !=0) {
            myAnnotation1 = [[MyAnnotation alloc] init];
            if ([[delarsInfoArray objectAtIndex:i] count] == 0) {

                myAnnotation1.title  = @"";
                myAnnotation1.subtitle = @"";
            }
            else
            {
                // NSLog(@"====== delears array is===%@",delarsInfoArray);
                NSLog(@"===== delears array count is %d",[delarsInfoArray count]);

                if ([[[delarsInfoArray objectAtIndex:i]valueForKey:@"Address"]objectAtIndex:2] !=nil)
                {
                    myAnnotation1.title = [[[delarsInfoArray objectAtIndex:i]valueForKey:@"Address"]objectAtIndex:2];
                }
                if ([[[delarsInfoArray objectAtIndex:i]valueForKey:@"City"]objectAtIndex:3]!= nil) {
                    myAnnotation1.subtitle = [[[delarsInfoArray objectAtIndex:i]valueForKey:@"City"]objectAtIndex:3];
                }

                NSLog(@"%@",[[[delarsInfoArray objectAtIndex:i]valueForKey:@"City"]objectAtIndex:3]);
            }

            [dealerMapView setRegion:mapRegion animated:YES];
            [dealerMapView addAnnotation:myAnnotation1];
            myAnnotation1.coordinate = mapRegion.center;
            [myAnnotation1 release];
        }
    }
}

上面的代码是在viewWillAppear中写的。在将地图加载到视图后，当我点击map.app时会崩溃。如何解决这个崩溃问题？

Answer 1

这里有很多问题，但跳出列表顶部的问题是：

if ([[[delarsInfoArray objectAtIndex:i]valueForKey:@"Address"]objectAtIndex:2] !=nil)
    ...

和

if ([[[delarsInfoArray objectAtIndex:i]valueForKey:@"City"]objectAtIndex:3]!= nil) {
    ...

问题是objectAtIndex数组的valueForKey 永远不会为nil。您无法在数组中存储nil，因此valueForKey的作用是，如果找不到值，则使用NSNull对象[NSNull null]。这表示找不到任何值，但使用NSNull（可以添加到数组中）而不是nil（不能）。

问题可能是有一些后续代码（例如，尝试计算出标注气泡大小的代码）试图获取字符串的长度，但是因为你存储了{{1}它试图调用NSNull方法并且它失败了。

您可以通过多种方式解决此问题，例如：

length

当我点击地图时，它会在iOS5的初始时间崩溃吗？

1 个答案: