Question

下面的代码暂时存储文件（我想在缓存中）但是我需要永久存储文件，我该怎么办？

public void downloadFile(){
            StorageReference islandRef = storageRef.child("cliff.jpg");
            File localFile = null;
            try {
                File cacheDir = getApplicationContext().getCacheDir();
                localFile = File.createTempFile("images", ".jpg", cacheDir);
            } catch (IOException e) {
                e.printStackTrace();
            }
            islandRef.getFile(localFile).addOnSuccessListener(new OnSuccessListener<FileDownloadTask.TaskSnapshot>() {
                @Override
                public void onSuccess(FileDownloadTask.TaskSnapshot taskSnapshot) {


                }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception exception) {
                // Handle any errors
                Log.i("msg", exception.toString());
                Toast.makeText(getApplicationContext(), "Failed", Toast.LENGTH_SHORT).show();

            }
        });

Answer 1

我们说话有多久？如果应用程序已卸载，数据是否仍然存在？一种解决方案是将数据存储在内部存储中（只有应用程序可访问，并在卸载应用程序时删除），方法是更改：

func obtainKeyData(tag: String) -> NSData? {
    var keyRef: AnyObject?
    let query: Dictionary<String, AnyObject> = [
        String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
        String(kSecReturnData): kCFBooleanTrue as CFBoolean,
        String(kSecClass): kSecClassKey as CFStringRef,
        String(kSecAttrApplicationTag): tag as CFStringRef,
        ]

    let result: NSData?

    switch SecItemCopyMatching(query, &keyRef) {
    case noErr:
        result = keyRef as? NSData
    default:
        result = nil
    }

    return result
}

func insertPublicKey(publicTag: String, data: NSData) -> SecKeyRef? {
    let query: Dictionary<String, AnyObject> = [
        String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
        String(kSecClass): kSecClassKey as CFStringRef,
        String(kSecAttrApplicationTag): publicTag as CFStringRef,
        String(kSecValueData): data as CFDataRef,
        String(kSecReturnPersistentRef): true as CFBooleanRef]

    var persistentRef: AnyObject?
    let status = SecItemAdd(query, &persistentRef)

    if status != noErr && status != errSecDuplicateItem {
        return nil
    }

    return obtainKey(publicTag)
}
func obtainKey(tag: String) -> SecKey? {
    var keyRef: AnyObject?
    let query: Dictionary<String, AnyObject> = [
        String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
        String(kSecReturnRef): kCFBooleanTrue as CFBoolean,
        String(kSecClass): kSecClassKey as CFStringRef,
        String(kSecAttrApplicationTag): tag as CFStringRef,
        ]

    let status = SecItemCopyMatching(query, &keyRef)

    switch status {
    case noErr:
        if let ref = keyRef {
            return (ref as! SecKeyRef)
        }
    default:
        break
    }

    return nil
}

到

File cacheDir = getApplicationContext().getCacheDir();

Answer 2

如果你想要一个你自己和其他应用程序可以轻松访问的文件，你应该获得外部存储的根目录并在那里创建文件夹......就像这样......

File externalRoot = Environment.getExternalStorageDirectory();
File dir = new File (externalRoot .getAbsolutePath() + "/parentFolder/childFolder");
dir.mkdirs();
File file = new File(dir, "filename");
...
FileOutputStream f = new FileOutputStream(file);
...

请记住，您应该检查存储是否可写。这将是其他应用程序可见的，如果您不想要这个

使用getApplicationContext().getFilesDir();来提供/data/data/com.package/files

之类的路径

Answer 3

为了保存图像，您必须通过这样做将其写入内部或外部存储：

而不是：

File cacheDir = getApplicationContext().getCacheDir();
localFile = File.createTempFile("images", ".jpg", cacheDir);

使用：

File cacheDir = getApplicationContext().getFilesDir();
localFile = new File("images.jpg", cacheDir);

我不知道firebase的StorageReference如何工作，但我推断.getFile将内容流式传输到文件中。在这种情况下，此代码应该起作用

永久存储文件

3 个答案: