主要是兼容7.0以后的fileProvider 把URI 以content provider 方式 对外提供的解析方法

   public static File getFileFromUri(Uri uri, Context context) {
        if (uri == null) {
            return null;
        }
        switch (uri.getScheme()) {
            case "content":
                return getFileFromContentUri(uri, context);
            case "file":
                return new File(uri.getPath());
            default:
                return null;
        }
    }

    /**
     * Gets the corresponding path to a file from the given content:// URI
     *
     * @param contentUri The content:// URI to find the file path from
     * @param context    Context
     * @return the file path as a string
     */

    private static File getFileFromContentUri(Uri contentUri, Context context) {
        if (contentUri == null) {
            return null;
        }
        File file = null;
        String filePath;
        String fileName;
        String[] filePathColumn = {MediaStore.MediaColumns.DATA, MediaStore.MediaColumns.DISPLAY_NAME};
        ContentResolver contentResolver = context.getContentResolver();
        Cursor cursor = contentResolver.query(contentUri, filePathColumn, null,
                null, null);
        if (cursor != null) {
            cursor.moveToFirst();
            try{
            filePath = cursor.getString(cursor.getColumnIndex(filePathColumn[0]));
            }catch(Exception e){
            }
            fileName = cursor.getString(cursor.getColumnIndex(filePathColumn[1]));
            cursor.close();
            if (!TextUtils.isEmpty(filePath)) {
                file = new File(filePath);
            }
            if (!file.exists() || file.length() <= 0 || TextUtils.isEmpty(filePath)) {
                filePath = getPathFromInputStreamUri(context, contentUri, fileName);
            }
            if (!TextUtils.isEmpty(filePath)) {
                file = new File(filePath);
            }
        }
        return file;
    }

    /**
     * 用流拷贝文件一份到自己APP目录下
     *
     * @param context
     * @param uri
     * @param fileName
     * @return
     */
    public static String getPathFromInputStreamUri(Context context, Uri uri, String fileName) {
        InputStream inputStream = null;
        String filePath = null;

        if (uri.getAuthority() != null) {
            try {
                inputStream = context.getContentResolver().openInputStream(uri);
                File file = createTemporalFileFrom(context, inputStream, fileName);
                filePath = file.getPath();

            } catch (Exception e) {
                L.e(e);
            } finally {
                try {
                    if (inputStream != null) {
                        inputStream.close();
                    }
                } catch (Exception e) {
                    L.e(e);
                }
            }
        }

        return filePath;
    }

    private static File createTemporalFileFrom(Context context, InputStream inputStream, String fileName)
            throws IOException {
        File targetFile = null;

        if (inputStream != null) {
            int read;
            byte[] buffer = new byte[8 * 1024];
            //自己定义拷贝文件路径
            targetFile = new File(getCacheDir(context), fileName);
            if (targetFile.exists()) {
                targetFile.delete();
            }
            OutputStream outputStream = new FileOutputStream(targetFile);

            while ((read = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, read);
            }
            outputStream.flush();

            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return targetFile;
    }

因为有拷贝文件和读取文件操作，所以在6.0以上需要申请权限