Android存儲訪問框架的使用小結

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存儲訪問框架，簡稱：SAF， 就是系統文件選擇器+文件操作API。先選擇文件，在用文件操作API處理文件。系統文件選擇器，就和Windows的文件選擇框一樣。

其實絕大多數app,都不會使用這個東西，因為太不方便瞭。圖片，視頻，普通文件，需要用戶去翻文件夾找，這樣的用戶體驗實在太差瞭。所以大傢都是用第三方的或者自己寫一個文件選擇器。

之所以講SAF，一，是因為Android11以後，使用MediaStore無法訪問到非多媒體文件瞭，需要依賴SAF瞭。二，外卡和SD卡的操作依賴於存儲訪問框架授權。

打開系統文件選擇器與文件過濾

 Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("application/*");
 
        startActivityForResult(intent, REQUEST_CODE)

setType的值是mime type, 可以是"image/*", "*/*",  其中*是通配符。"image/*"代碼所有類型的圖片。"*/*"代表所有類型的文件。

當隻需要打開幾種文件類型時，可以用Intent.EXTRA_MIME_TYPES。同時setType設成“*/*”。

Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("*/*");
        intent.putExtra(Intent.EXTRA_MIME_TYPES, new String[] {
                "application/pdf", // .pdf
                "application/vnd.oasis.opendocument.text", // .odt
                "text/plain" // .txt
        });
 
 
        startActivityForResult(intent, REQUEST_CODE)

Intent.ACTION_PICK和ACTION_GET_CONTENT，也可以打開文件選擇框。ACTION_GET_CONTENT更加寬泛，除瞭文件其他類型的內容還可以取。

 Intent intent = new Intent(Intent.ACTION_PICK,  
                    android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    intent.setType("image/*");
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("image/*")

下面列舉瞭所有的mime type:

private static final String[][] MIME_TYPES = new String[][]{
            {"3gp", "video/3gpp"},
            {"apk", "application/vnd.android.package-archive"},
            {"asf", "video/x-ms-asf"},
            {"avi", "video/x-msvideo"},
            {"bin", "application/octet-stream"},
            {"bmp", "image/bmp"},
            {"c", "text/plain"},
            {"class", "application/octet-stream"},
            {"conf", "text/plain"},
            {"cpp", "text/plain"},
            {"doc", "application/msword"},
            {"docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
            {"xls", "application/vnd.ms-excel"},
            {"xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
            {"exe", "application/octet-stream"},
            {"gif", "image/gif"},
            {"gtar", "application/x-gtar"},
            {"gz", "application/x-gzip"},
            {"h", "text/plain"},
            {"htm", "text/html"},
            {"html", "text/html"},
            {"jar", "application/java-archive"},
            {"java", "text/plain"},
            {"jpeg", "image/jpeg"},
            {"jpg", "image/jpeg"},
            {"js", "application/x-JavaScript"},
            {"log", "text/plain"},
            {"m3u", "audio/x-mpegurl"},
            {"m4a", "audio/mp4a-latm"},
            {"m4b", "audio/mp4a-latm"},
            {"m4p", "audio/mp4a-latm"},
            {"ape", "audio/ape"},
            {"flac", "audio/flac"},
            {"m4u", "video/vnd.mpegurl"},
            {"m4v", "video/x-m4v"},
            {"mov", "video/quicktime"},
            {"mp2", "audio/x-mpeg"},
            {"mp3", "audio/x-mpeg"},
            {"mp4", "video/mp4"},
            {"mkv", "video/x-matroska"},
            {"flv", "video/x-flv"},
            {"divx", "video/x-divx"},
            {"mpa", "video/mpeg"},
            {"mpc", "application/vnd.mpohun.certificate"},
            {"mpe", "video/mpeg"},
            {"mpeg", "video/mpeg"},
            {"mpg", "video/mpeg"},
            {"mpg4", "video/mp4"},
            {"mpga", "audio/mpeg"},
            {"msg", "application/vnd.ms-outlook"},
            {"ogg", "audio/ogg"},
            {"pdf", "application/pdf"},
            {"png", "image/png"},
            {"pps", "application/vnd.ms-powerpoint"},
            {"ppt", "application/vnd.ms-powerpoint"},
            {"pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"},
            {"prop", "text/plain"},
            {"rc", "text/plain"},
            {"rmvb", "audio/x-pn-realaudio"},
            {"rtf", "application/rtf"},
            {"sh", "text/plain"},
            {"tar", "application/x-tar"},
            {"tgz", "application/x-compressed"},
            {"txt", "text/plain"},
            {"wav", "audio/x-wav"},
            {"wma", "audio/x-ms-wma"},
            {"wmv", "audio/x-ms-wmv"},
            {"wps", "application/vnd.ms-works"},
            {"xml", "text/plain"},
            {"z", "application/x-compress"},
            {"zip", "application/x-zip-compressed"},
            {"rar", "application/x-rar"},
            {"", "*/*"}
    };

打開指定文件夾

利用DocumentsContract.EXTRA_INITIAL_URI，在打開文件選擇器的時候，跳轉到指定文件夾。隻有android 8以上才行。

Uri uri = Uri.parse("content://com.android.externalstorage.documents/document/primary:Download");
Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
intent.addCategory(Intent.CATEGORY_OPENABLE);
intent.setType("*/*");
intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uri);
startActivityForResult(intent, 1);

文件夾權限申請

當需要讀取非公共文件夾裡面的文件時，可以申請授權，授權後保存Uri，之後可以拼接這個Uri操作文件夾裡的所有文件。

尤其是SD卡，從Android 5 開始文件的修改刪除必須先授權，且必須通過SVF框架接口才能操作。

可以使用EXTRA_INITIAL_URI，打開指定文件夾，讓用戶授權

  Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
       Uri uri = Uri.parse("content://com.android.externalstorage.documents/document/primary:Download");
 
       intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uri);
 
        startActivityForResult(intent)

需要註意的是，Android 11以後，無法授權訪問存儲根目錄，以及Download/，Android/, 這兩個文件夾也無法授權。

創建文件夾

創建文件夾有兩個情況，一個是在已授權的文件夾下，可以使用SVF框架API。 

DocumentsContract.createDocument()

還有一種是在無授權的文件夾下創建，那麼可以直接指定類型和名字，通過跳系統選擇框創建。

 Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("application/txt");
        intent.putExtra(Intent.EXTRA_TITLE, "testfile.txt");
 
        startActivityForResult(intent)

存儲訪問框架API

存儲訪問框架API，都在DocumentsContract裡面，典型的有：

public static @Nullable Uri renameDocument(@NonNull ContentResolver content,
            @NonNull Uri documentUri, @NonNull String displayName) throws FileNotFoundException {
 
    }
 
    /**
     * Delete the given document.
     *
     * @param documentUri document with {@link Document#FLAG_SUPPORTS_DELETE}
     * @return if the document was deleted successfully.
     */
    public static boolean deleteDocument(@NonNull ContentResolver content, @NonNull Uri documentUri)
            throws FileNotFoundException {
 
    }
 
    /**
     * Copies the given document.
     *
     * @param sourceDocumentUri document with {@link Document#FLAG_SUPPORTS_COPY}
     * @param targetParentDocumentUri document which will become a parent of the source
     *         document's copy.
     * @return the copied document, or {@code null} if failed.
     */
    public static @Nullable Uri copyDocument(@NonNull ContentResolver content,
            @NonNull Uri sourceDocumentUri, @NonNull Uri targetParentDocumentUri)
            throws FileNotFoundException {
 
    }
 
    /**
     * Moves the given document under a new parent.
     *
     * @param sourceDocumentUri document with {@link Document#FLAG_SUPPORTS_MOVE}
     * @param sourceParentDocumentUri parent document of the document to move.
     * @param targetParentDocumentUri document which will become a new parent of the source
     *         document.
     * @return the moved document, or {@code null} if failed.
     */
    public static @Nullable Uri moveDocument(@NonNull ContentResolver content,
            @NonNull Uri sourceDocumentUri, @NonNull Uri sourceParentDocumentUri,
            @NonNull Uri targetParentDocumentUri) throws FileNotFoundException {
 
    }
 
    /**
     * Removes the given document from a parent directory.
     *
     * <p>In contrast to {@link #deleteDocument} it requires specifying the parent.
     * This method is especially useful if the document can be in multiple parents.
     *
     * @param documentUri document with {@link Document#FLAG_SUPPORTS_REMOVE}
     * @param parentDocumentUri parent document of the document to remove.
     * @return true if the document was removed successfully.
     */
    public static boolean removeDocument(@NonNull ContentResolver content, @NonNull Uri documentUri,
            @NonNull Uri parentDocumentUri) throws FileNotFoundException {
 
    }

獲取文件夾文件

使用DocumentFile類獲取文件夾裡文件列表。

private ActivityResultLauncher<Object> openFile() {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
        Uri uri = Uri.parse("content://com.android.externalstorage.documents/document/primary:AuthSDK");
        intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uri);
        return startActivityForResult(intent, new ActivityResultCallback<Intent>() {
            @Override
            public void onActivityResult(Intent result) {
 
                for (DocumentFile documentFile : DocumentFile.fromTreeUri(BaseApplication.getInstance().getApplicationContext(), Uri.parse(result.getData().toString())).listFiles()) {
 
                     Log.i("", documentFile.getUri());
                }
            }
        });
    }

下面的代碼演示瞭，使用SVF讀取文件內容，寫內容，通過MediaStore查詢文件屬性。

private ActivityResultLauncher<Object> openFile() {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
        Uri uri = Uri.parse("content://com.android.externalstorage.documents/document/primary:AuthSDK");
        intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uri);
 
        return startActivityForResult(intent, new ActivityResultCallback<Intent>() {
            @Override
            public void onActivityResult(Intent result) {
 
                for (DocumentFile documentFile : DocumentFile.fromTreeUri(BaseApplication.getInstance().getApplicationContext(), Uri.parse(result.getData().toString())).listFiles()) {
                    try {
                        InputStream inputStream = BaseApplication.getInstance().getContentResolver().openInputStream(documentFile.getUri());
                        byte[] readData = new byte[1024];
                        inputStream.read(readData);
 
                        OutputStream outputStream = BaseApplication.getInstance().getContentResolver().openOutputStream(documentFile.getUri());
                        byte[] writeData = "alan gong".getBytes(StandardCharsets.UTF_8);
                        outputStream.write(writeData, 0, 9);
                        outputStream.close();
                        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                            Uri mediaUri = MediaStore.getMediaUri(BaseApplication.getInstance().getApplicationContext(), documentFile.getUri());
                            long fileId = ContentUris.parseId(mediaUri);
                            Cursor query = BaseApplication.getInstance().getContentResolver().query(documentFile.getUri(), null, MediaStore.MediaColumns._ID + "=" + fileId, null, null);
                            int columnIndex = query.getColumnIndexOrThrow(MediaStore.MediaColumns.MIME_TYPE);
                            String mimeType = query.getString(columnIndex);
                            Log.i("", "");
                        }
 
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }

使用MediaStore.getMediaUri(documentUri)可以轉換，MediaStore Uri 和 Document Uri。通過MediaStore Uri中的數據庫id，就可以查詢文件的所有屬性瞭。

MediaStore Uri：content://media/external_primary/file/101750

Document Uri: content://com.android.externalstorage.documents/tree/primary%3AAuthSDK

另外，

非公共目錄下不能用File API操作的，即使通過SVF授權瞭， READ_EXTRNAL_PERMISSION的權限也給瞭。還是會拋出FileNotFoundException， 並且顯示permission deny。

和MediaStore API的不同

存儲訪問框架API和MediaStore API的差異，在於存儲訪問框架API，是基於系統文件選擇框的，用戶選擇瞭文件，那麼相當於授權瞭， 可以訪問所有類型的文件。而MediaStore的特點是可以查詢出所有文件，但是開啟分區存儲後，隻能查處多媒體文件，其他類型文件是不可以的。

到此這篇關於Android存儲訪問框架的使用的文章就介紹到這瞭,更多相關Android存儲訪問框架內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet！

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