根据uri获取绝对路径

在开发过程中常用到选择图片，文件的功能。打开文件选择器选择文件之后返回的可能并不是文件路径，而是content://开头的Uri，这时如果要访问这个文件就需要把Uri转为绝对路径。

public class FileUtil {

    /**
     * 根据Uri获取图片绝对路径
     * @param context context
     * @param uri     uri
     */
    public static String getFileAbsolutePath(Context context, Uri uri) {
        if (context == null || uri == null) return null;
        // DocumentProvider
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT && DocumentsContract.isDocumentUri(context, uri)) {
            if (isExternalStorageDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];
                if ("primary".equalsIgnoreCase(type)) {
                    return Environment.getExternalStorageDirectory() + "/" + split[1];
                }else if ("home".equalsIgnoreCase(type)) {
                    return Environment.getExternalStorageDirectory() + "/documents/" + split[1];
                }
            } else if (isDownloadsDocument(uri)) {
                // DownloadsProvider
                final String id = DocumentsContract.getDocumentId(uri);
                if (TextUtils.isEmpty(id)) {
                    return null;
                }
                if (id.startsWith("raw:")) {
                    return id.substring(4);
                }
                String[] contentUriPrefixesToTry = new String[]{
                        "content://downloads/public_downloads",
                        "content://downloads/my_downloads",
                        "content://downloads/all_downloads"
                };
                for (String contentUriPrefix : contentUriPrefixesToTry) {
                    try {
                        Uri contentUri = ContentUris.withAppendedId(Uri.parse(contentUriPrefix), Long.valueOf(id));
                        String path = getDataColumn(context, contentUri, null, null);
                        if (path != null) {
                            return path;
                        }
                    } catch (Exception ignore) {
                    }
                }
                try {
                    String path = getDataColumn(context, uri, null, null);
                    if (path != null) {
                        return path;
                    }
                } catch (Exception ignore) {
                }
                // path could not be retrieved using ContentResolver, therefore copy file to accessible cache using streams
                return null;
            } else if (isMediaDocument(uri)) {
                // MediaProvider
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];

                Uri contentUri;
                switch (type.toLowerCase(Locale.ENGLISH)) {
                    case "image":
                        contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                        break;
                    case "video":
                        contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
                        break;
                    case "audio":
                        contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
                        break;
                    default:
                        contentUri = MediaStore.Files.getContentUri("external");
                        break;
                }
                final String selection = MediaStore.MediaColumns._ID +"=?";
                final String[] selectionArgs = new String[]{split[1]};
                return getDataColumn(context, contentUri, selection, selectionArgs);
            }
        } else if (ContentResolver.SCHEME_CONTENT.equalsIgnoreCase(uri.getScheme())) {
            // MediaStore (and general)
            // Return the remote address
            if (isGooglePhotosUri(uri)) {
                return uri.getLastPathSegment();
            }
            return getDataColumn(context, uri, null, null);
        } else if (ContentResolver.SCHEME_FILE.equalsIgnoreCase(uri.getScheme())) {
            // File
            return uri.getPath();
        }
        return null;
    }

    /**
     * 通过游标获取当前文件路径
     * @param context       context
     * @param uri           uri
     * @param selection     selection
     * @param selectionArgs selectionArgs
     * @return 路径，未找到返回null
     */
    public static String getDataColumn(Context context, @NonNull Uri uri, String selection, String[] selectionArgs) {
        Cursor cursor = null;
        String column = MediaStore.Images.Media.DATA;
        String[] projection = {column};
        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
            if (cursor != null && cursor.moveToFirst()) {
                int index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(index);
            }
        } catch (Exception ignore) {
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return null;
    }

    public static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    public static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    public static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }

    public static boolean isGooglePhotosUri(Uri uri) {
        return "com.google.android.apps.photos.content".equals(uri.getAuthority());
    }
}

需要注意的是，不要忘记添加文件读权限并添加动态请求权限；如果修改下载文件夹下的文件，需要添加权限