本文将带你了解IOS开发入门iOS NSURLSessionDownloadTask 报错 Invalid resume data for background download. Background downloads mu，希望本文对大家学IOS有所帮助。

错误： Invalid resume data for   background download. Background downloads must use http or https and must   download to an accessible   file.

网上好多说这个错误在ios10中出现，如果调试的时候，点暂停下载，再重新发布到手机上，再点击开始下载，也会有这个错误。

解决办法：自定义一个NSURLSession分类，在ios10代替-   (NSURLSessionDownloadTask *)downloadTaskWithResumeData:(NSData   *)resumeData;

NSURLSession+TYCorrectedResumeData.h

#import <foundation foundation.h="">

@interface NSURLSession   (TYCorrectedResumeData)

-   (NSURLSessionDownloadTask *)downloadTaskWithCorrectResumeData:(NSData   *)resumeData;

@end</foundation>

NSURLSession+TYCorrectedResumeData.m

//

//    NSURLSession+TYCorrectedResumeData.m

//    TYDownloadManagerDemo

//

//    Created by tanyang on 2016/10/7.

//  Copyright ? 2016年 tany. All rights   reserved.

//

#import "NSURLSession+TYCorrectedResumeData.h"

#import <uikit uikit.h="">

#define IS_IOS10ORLATER ([[[UIDevice currentDevice]   systemVersion] floatValue] >= 10)

@implementation NSURLSession   (TYCorrectedResumeData)

-   (NSURLSessionDownloadTask *)downloadTaskWithCorrectResumeData:(NSData   *)resumeData {

    NSString *kResumeCurrentRequest =   @"NSURLSessionResumeCurrentRequest";

    NSString *kResumeOriginalRequest =   @"NSURLSessionResumeOriginalRequest";

    NSData *cData =   correctResumeData(resumeData);

    cData =   cData?cData:resumeData;

    NSURLSessionDownloadTask *task = [self   downloadTaskWithResumeData:cData];

    NSMutableDictionary *resumeDic =   getResumeDictionary(cData);

    if (resumeDic) {

        if (task.originalRequest == nil)   {

            NSData *originalReqData =   resumeDic[kResumeOriginalRequest];

            NSURLRequest *originalRequest =   [NSKeyedUnarchiver unarchiveObjectWithData:originalReqData   ];

            if (originalRequest) {

                [task setValue:originalRequest   forKey:@"originalRequest"];

            }

        }

        if (task.currentRequest == nil) {

            NSData *currentReqData =   resumeDic[kResumeCurrentRequest];

            NSURLRequest *currentRequest =   [NSKeyedUnarchiver unarchiveObjectWithData:currentReqData];

            if (currentRequest) {

                [task setValue:currentRequest forKey:@"currentRequest"];

            }

        }

    }

    return task;

}

#pragma mark- private

NSData * correctRequestData(NSData *data)   {

    if (!data) {

        return nil;

    }

    // return the same data if it's   correct

    if ([NSKeyedUnarchiver unarchiveObjectWithData:data] != nil)   {

        return data;

    }

    NSMutableDictionary *archive =   [[NSPropertyListSerialization propertyListWithData:data   options:NSPropertyListMutableContainersAndLeaves format:nil error:nil]   mutableCopy];

    if (!archive) {

        return nil;

    }

    NSInteger k = 0;

    id objectss = archive[@"$objects"];

    while ([objectss[1] objectForKey:[NSString stringWithFormat:@"$%ld",k]] != nil)   {

        k += 1;

    }

    NSInteger i = 0;

    while ([archive[@"$objects"][1]   objectForKey:[NSString stringWithFormat:@"__nsurlrequest_proto_prop_obj_%ld",i]] != nil)   {

        NSMutableArray *arr =   archive[@"$objects"];

        NSMutableDictionary *dic =   arr[1];

        id obj = [dic objectForKey:[NSString   stringWithFormat:@"__nsurlrequest_proto_prop_obj_%ld",i]];

        if (obj) {

            [dic setValue:obj forKey:[NSString   stringWithFormat:@"$%ld",i+k]];

            [dic removeObjectForKey:[NSString   stringWithFormat:@"__nsurlrequest_proto_prop_obj_%ld",i]];

            [arr   replaceObjectAtIndex:1 withObject:dic];

            archive[@"$objects"] = arr;

        }

        i++;

    }

    if ([archive[@"$objects"][1]   objectForKey:@"__nsurlrequest_proto_props"] != nil) {

        NSMutableArray *arr =   archive[@"$objects"];

        NSMutableDictionary *dic =   arr[1];

        id obj = [dic   objectForKey:@"__nsurlrequest_proto_props"];

        if (obj) {

            [dic setValue:obj forKey:[NSString   stringWithFormat:@"$%ld",i+k]];

            [dic removeObjectForKey:@"__nsurlrequest_proto_props"];

            [arr   replaceObjectAtIndex:1   withObject:dic];

            archive[@"$objects"] = arr;

        }

    }

    // Rectify weird   "NSKeyedArchiveRootObjectKey" top key to   NSKeyedArchiveRootObjectKey =   "root"

    if ([archive[@"$top"] objectForKey:@"NSKeyedArchiveRootObjectKey"] != nil) {

        [archive[@"$top"] setObject:archive[@"$top"][@"NSKeyedArchiveRootObjectKey"] forKey:   NSKeyedArchiveRootObjectKey];

        [archive[@"$top"] removeObjectForKey:@"NSKeyedArchiveRootObjectKey"];

    }

    // Reencode archived   object

    NSData *result = [NSPropertyListSerialization   dataWithPropertyList:archive format:NSPropertyListBinaryFormat_v1_0   options:0   error:nil];

    return result;

}

NSMutableDictionary *getResumeDictionary(NSData *data)   {

    NSMutableDictionary *iresumeDictionary =   nil;

    if (IS_IOS10ORLATER) {

        id root =   nil;

        id  keyedUnarchiver =   [[NSKeyedUnarchiver alloc]   initForReadingWithData:data];

        @try {

            root = [keyedUnarchiver   decodeTopLevelObjectForKey:@"NSKeyedArchiveRootObjectKey" error:nil];

            if (root == nil) {

                root = [keyedUnarchiver   decodeTopLevelObjectForKey:NSKeyedArchiveRootObjectKey error:nil];

            }

        } @catch(NSException *exception) {

        }

        [keyedUnarchiver finishDecoding];

        iresumeDictionary = [root   mutableCopy];

    }

    if (iresumeDictionary == nil) {

        iresumeDictionary =   [NSPropertyListSerialization propertyListWithData:data   options:NSPropertyListMutableContainersAndLeaves format:nil   error:nil];

    }

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