How to show the progress of copying a large file i

问题:

I am writing an iOS app. In my app, I want to copy some files from one folder to another. But because some files is too large, it will take a long time to finish the copy. So I want to add a progress bar to show the percentage of the copy. But I find that the file manager has no callback method to get the percentage. Does anyone have the good solution to it?

回答1:

In high level :

1. Run your copying process in a seperate thread (T1)
2. Run another thread (T2) which reads periodically (say every 100ms) the destination file current_size.
3. Calculate the percentage : current_size / total_size
4. Update you progress bar ui element

回答2:

I've created a simple class with @giorashc approach.

If anyone needs something like this feel free to use it.

The .h

#import <UIKit/UIKit.h>

@protocol IDCopyUtilsDelegate;

@interface IDCopyUtils : NSObject

@property (nonatomic, weak) id<IDCopyUtilsDelegate> delegate;

- (void)copyFileAtPath:(NSString *)sourcePath toPath:(NSString *)targetPath;

@end

// 3. Definition of the delegate's interface
@protocol IDCopyUtilsDelegate <NSObject>

- (void)setCopyProgress:(float)progress;
- (void)didFinishedCopyWithError:(NSError *)error;

@end

The .m

#import "IDCopyUtils.h"

@interface IDCopyUtils()

@property (nonatomic, strong) NSTimer *timer;
@property (nonatomic, strong) NSString *sourcePath;
@property (nonatomic, strong) NSString *targetPath;

@end

@implementation IDCopyUtils

- (void)copyFileAtPath:(NSString *)sourcePath toPath:(NSString *)targetPath
{
    self.sourcePath = sourcePath;
    self.targetPath = targetPath;

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;

    if ([fileManager fileExistsAtPath:self.targetPath] == YES) {
        [fileManager removeItemAtPath:self.targetPath error:&error];
    }

    self.timer = [NSTimer scheduledTimerWithTimeInterval:0.100
                                     target:self
                                   selector:@selector(checkFileSize)
                                   userInfo:nil
                                    repeats:YES];

    [self performSelector:@selector(startCopy) withObject:nil afterDelay:0.5];

}

- (void)checkFileSize
{
    dispatch_async(dispatch_get_main_queue(), ^{
        NSDictionary *attributesSource = [[NSFileManager defaultManager] attributesOfItemAtPath:self.sourcePath error:NULL]; unsigned long long fileSize = [attributesSource fileSize];

        NSDictionary *attributesTarget = [[NSFileManager defaultManager] attributesOfItemAtPath:self.targetPath error:NULL]; unsigned long long fileSizeTarget = [attributesTarget fileSize];

        double progress = (float)fileSizeTarget / (float)fileSize;

        if (self.delegate && [self.delegate respondsToSelector:@selector(setCopyProgress:)])
        {
            [self.delegate setCopyProgress:progress];
        }

        NSLog(@"Size: %f", progress);
    });
}

- (void)startCopy
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSError *error;

        if ([fileManager fileExistsAtPath:self.targetPath] == YES) {
            [fileManager removeItemAtPath:self.targetPath error:&error];
        }

        if ([fileManager fileExistsAtPath:self.targetPath] == NO) {
            [fileManager copyItemAtPath:self.sourcePath toPath:self.targetPath error:&error];

            [self.timer invalidate];
            self.timer = nil;

            if (self.delegate && [self.delegate respondsToSelector:@selector(didFinishedCopyWithError:)])
            {
                [self.delegate didFinishedCopyWithError:error];
            }
        }
    });
}

@end

You can use it like this (for example):

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

NSString *sourcePath = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"iso"];
NSString *targetPath = [documentsDirectory stringByAppendingPathComponent:@"test.iso"];

IDCopyUtils *copyUtils = [[IDCopyUtils alloc] init];
copyUtils.delegate = self;
[copyUtils copyFileAtPath:sourcePath toPath:targetPath];

And you will we able to update you progress view and get notified when the file did finidhed copying using the delegate methods.