目标-c：无法将图像写入文档目录答案

【问题标题】：objective-c: failed to write image to documents directory目标-c：无法将图像写入文档目录
【发布时间】：2012-04-14 00:56:37
【问题描述】：

我正在使用这段代码尝试将图像保存到文档目录：

//FOR TESTING ON SIMULATOR 
UIImage* image = [UIImage imageNamed:@"ReceiptImage1.jpg"];
NSData *imageData = UIImagePNGRepresentation(image);
NSString* imageName = @"Receipt1Image1.png";
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
NSString* fullPathToFile = [documentsDirectory stringByAppendingPathComponent:imageName];        
[imageData writeToFile:fullPathToFile atomically:NO];

self.receiptImage1 = fullPathToFile;

self.receiptImageView1.image = [UIImage imageWithContentsOfFile:fullPathToFile];

NSLog(@"fullPathToFile %@", fullPathToFile);

但是，这段代码并未将 imageViews 图像设置为我尝试写入文档目录的收据图像。

谁能解释我做错了什么以及如何解决它？

谢谢，

杰克

【问题讨论】：

你检查writeToFile:atomically:的返回值了吗？如果有错误，您可以使用writeToFile:options:error: 变体检查它是什么。
另外，为什么您实际上需要将图像从应用程序包复制到文档目录？
您在设备中检查过您的代码吗？因为模拟器不会逐行执行代码..[imageData writeToFile:fullPathToFile atomically:NO];方法需要一些时间将图像写入路径，所以尝试在一段时间后将图像加载到图像中
您的代码运行良好。请查看 IBOutlet 以获取receiptImageView1。
@MrTJ 成功将图像保存到文档目录后，我将更改代码以从相机/照片中获取图像，这仅用于在模拟器上进行测试。谢谢大家。

标签： iphone objective-c ios uiimageview nsdocumentdirectory

【解决方案1】：

使用这个：

- (void)saveImage:(UIImage*)image:(NSString*)imageName{
NSData *imageData = UIImagePNGRepresentation(image); //convert image into .png format.

NSFileManager *fileManager = [NSFileManager defaultManager];//create instance of NSFileManager

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); //create an array and store result of our search for the documents directory in it

NSString *documentsDirectory = [paths objectAtIndex:0]; //create NSString object, that holds our exact path to the documents directory

NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", imageName]]; //add our image to the path 

[fileManager createFileAtPath:fullPath contents:imageData attributes:nil]; //finally save the path (image)

NSLog(@"image saved");}

【讨论】：

【解决方案2】：

先原子写入文件，再尝试：

self.receiptImage1 = [UIImage imageWithContentsOfFile:fullPathToFile];
self.receiptImageView1 = [UIImageView initWithImage:self.receiptImage1];

【讨论】：

【解决方案3】：

如果已经存在文件，它可能不会保存到该路径。（查看 API 文档，我记不清了。但为了保存，您应该添加如下内容：

    NSArray *dirs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [dirs objectAtIndex:0];
    _exportPath = [documentsDirectoryPath stringByAppendingPathComponent:aFileName];  // may need to hang onto him

    if ([[NSFileManager defaultManager] fileExistsAtPath:_exportPath]) {
        [[NSFileManager defaultManager] removeItemAtPath:_exportPath
                                                   error:nil];
    }

【讨论】：

【解决方案4】：

您可以采取以下方法

-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    if ([[extension lowercaseString] isEqualToString:@"png"]) {
        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
    } else {
        ALog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
    }
}

要保存图像，只需这样做：

NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
[self saveImage:yourImage withFileName:@"Your Image Name" ofType:@"png" inDirectory:path];

要加载图像，请实现此方法：

-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {

    UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];

    return result;
}

然后像这样使用它：

NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
yourImage.image = [self loadImage:@"Your Image Name" ofType:@"png" inDirectory:path];

或者您可以简单地将您的图像设置为等于此方法返回的内容，而不是创建一个方法：

NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
yourImage.image = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/Your Image Name.png", path]];

【讨论】：