IOS學習筆記22—檔案操作（NSFileManager）結合相冊小例子

這個示例程式主要用到了IOS中的UIImageView、UIImagePickerViewController、UIImage、NSFileManager等知識，結合這些知識構成一個小的應用程式，主要功能是對相冊圖檔進行讀取、存儲到指定檔案夾、從指定檔案夾讀取出來。這方面的知識在正式項目中用的是比較多的。做Android開發中，經常會使用到将圖檔儲存到SD卡和從SD卡讀取圖檔的操作，相比于Android在這方面的操作，IOS要友善許多。

基本功能是從相冊選取一張圖檔，選完後顯示在界面的UIImageView控件中，點選儲存到檔案夾按鈕後就将圖檔儲存到Documents下的ImageFile檔案夾中，以image.png命名。退出程式下次進來時，可以選擇從檔案夾讀取圖檔，如果有則讀取出來顯示在UIImageView上，如果沒有則提示檔案不存在。

首先來看看最後效果：

·從相冊選取圖檔後顯示在界面上

這裡對功能進行了一點改進，點選打開相冊按鈕後出來一個UIActionSheet操作選項框，可以選擇是從相機擷取圖檔還是從相冊擷取。代碼也做出了一點修改。

·點選儲存到檔案夾按鈕後提示資訊

·點選讀取圖檔按鈕後的提示資訊（圖檔不存在）

·如果存在則将圖檔顯示出來

儲存圖檔成功後，按照前一篇文章提到的方法，可以到Finder下檢視檔案資訊：

下面是實作部分，首先看看布局檔案：

下面是代碼：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIImagePickerControllerDelegate,UINavigationControllerDelegate,UIActionSheetDelegate>

@property (retain, nonatomic) IBOutlet UIImageView *imageView;
@property (retain, nonatomic) UIButton *saveToFileButton;

//打開相冊
- (IBAction)openAlbum:(id)sender;

//從檔案夾讀取圖檔
- (IBAction)readImage:(id)sender;

@end
           

下面是ViewController.m檔案

#import "ViewController.h"
//儲存到檔案夾按鈕的标簽，選取圖檔前，這個按鈕是隐藏的
#define SAVE_BUTTON_TAG 101

@interface ViewController ()

@end

@implementation ViewController
@synthesize imageView = _imageView;
@synthesize saveToFileButton = _saveToFileButton;

- (void)viewDidLoad
{
    [super viewDidLoad];
    //根據設定的tag擷取按鈕控件
    self.saveToFileButton = (UIButton *)[self.view viewWithTag:SAVE_BUTTON_TAG];
    //添加對象事件
    [self.saveToFileButton addTarget:self action:@selector(saveToFileBtnTapped:) forControlEvents:UIControlEventTouchUpInside];
    //設定為不可見
    self.saveToFileButton.hidden = YES;
}

- (void)viewDidUnload
{
    [self setImageView:nil];
    [self setSaveToFileButton:nil];
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void)dealloc {
    [self.imageView release];
    [self.saveToFileButton release];
    [super dealloc];
}

- (IBAction)openAlbum:(id)sender {
    UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"選擇圖檔" delegate:self cancelButtonTitle:@"取消" destructiveButtonTitle:nil otherButtonTitles:@"拍照",@"相冊", nil];
    [actionSheet showInView:self.view];
    [actionSheet release];
}

//從檔案夾讀取圖檔
- (IBAction)readImage:(id)sender {
    NSString *imagePath = [self imageSavedPath:@"image.png"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    //判斷檔案是否存在
    if (![fileManager fileExistsAtPath:imagePath]) {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Note" message:@"檔案不存在" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alertView show];
        [alertView release];
    }else {
        //從指定目錄讀取圖檔
        UIImage *image = [UIImage imageWithContentsOfFile:imagePath];
        self.imageView.image = image;
    }
}

//儲存到檔案按鈕事件
- (void)saveToFileBtnTapped:(id)sender {
    NSString *imagePath = [self imageSavedPath:@"image.png"];
    BOOL isSaveSuccess = [self saveToDocument:self.imageView.image withFilePath:imagePath];
    
    if (isSaveSuccess) {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"操作結果" message:@"儲存圖檔成功" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alertView show];
        [alertView release];
    }else {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"操作結果" message:@"儲存圖檔失敗" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alertView show];
        [alertView release];
    }
}

//将選取的圖檔儲存到目錄檔案夾下
-(BOOL)saveToDocument:(UIImage *) image withFilePath:(NSString *) filePath
{
    if ((image == nil) || (filePath == nil) || [filePath isEqualToString:@""]) {
        return NO;
    }
    
    @try {
        NSData *imageData = nil;
        //擷取檔案擴充名
        NSString *extention = [filePath pathExtension];
        if ([extention isEqualToString:@"png"]) {
            //傳回PNG格式的圖檔資料
            imageData = UIImagePNGRepresentation(image);
        }else{
            //傳回JPG格式的圖檔資料，第二個參數為壓縮品質：0:best 1:lost
            imageData = UIImageJPEGRepresentation(image, 0);
        }
        if (imageData == nil || [imageData length] <= 0) {
            return NO;
        }
        //将圖檔寫入指定路徑
        [imageData writeToFile:filePath atomically:YES];
        return  YES;
    }
    @catch (NSException *exception) {
        NSLog(@"儲存圖檔失敗");
    }
    
    return NO;
    
}

//根據圖檔名将圖檔儲存到ImageFile檔案夾中
-(NSString *)imageSavedPath:(NSString *) imageName
{
    //擷取Documents檔案夾目錄
    NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentPath = [path objectAtIndex:0];
    //擷取檔案管理器
    NSFileManager *fileManager = [NSFileManager defaultManager];
    //指定建立檔案夾路徑
    NSString *imageDocPath = [documentPath stringByAppendingPathComponent:@"ImageFile"];
    //建立ImageFile檔案夾
    [fileManager createDirectoryAtPath:imageDocPath withIntermediateDirectories:YES attributes:nil error:nil];
    //傳回儲存圖檔的路徑（圖檔儲存在ImageFile檔案夾下）
    NSString * imagePath = [imageDocPath stringByAppendingPathComponent:imageName];
    return imagePath;
}

#pragma Delegate method UIImagePickerControllerDelegate
//圖像選取器的委托方法，選完圖檔後回調該方法
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo
{
    if (image != nil) {
        //標明照片後在界面顯示照片并把儲存按鈕設為可見
        self.imageView.image = image;
        self.saveToFileButton.hidden = NO;
    }
    //關閉圖像選擇器
    [self dismissModalViewControllerAnimated:YES];
}

-(void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
    //擷取圖檔選取器
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
    //指定代理
    imagePicker.delegate = self;
    //打開圖檔後允許編輯
    imagePicker.allowsEditing = YES;
    
    //判斷圖檔源的類型
    if (buttonIndex == 0) {
        if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
            //相機
            imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
        }
    }else if (buttonIndex == 1) {
        if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]){
            //圖檔庫
            imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        }
//        if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeSavedPhotosAlbum]) {
//            //相冊
//            imagePicker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
//        }
    }else if (buttonIndex == [actionSheet cancelButtonIndex]) {
        return;
    }
    
    //打開圖檔選擇模态視圖
    [self presentModalViewController:imagePicker animated:YES];
    [imagePicker release];

}

@end
           

中間有些操作過程我就沒有一一例舉了，比如如何将控件與代碼關聯，如何設定控件的TAG等。需要代碼的朋友可以給我留言，我發你們郵箱！

加入我們的QQ群或微信公衆賬号請檢視： Ryan's zone公衆賬号及QQ群

歡迎關注我的新浪微網誌和我交流：@唐韌_Ryan