我遇到的问题是,我无法从搭载 Android 9 的智能手机上选择的文件中提取文件扩展名.该问题不会出现在搭载 Android 8 或更低版本的设备上.
The issue I have, is that i can't extract the file exetension from files choosen on a smartphone with Android 9. The problem doesn't appear on devices with Android 8 or less.
当用户选择了任何类型的文件时,onActivityResult 就会被调用.在这个方法中,我从 FileUtils 类调用 getPath,所以我可以提取文件扩展名.
When the user has choosen any kind of file the onActivityResult gets called. In this method I call getPath from FileUtils class, so I can extract the file extension.
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
Uri uri = new Uri.Builder().build();
if (resultCode == RESULT_OK) {
switch (requestCode) {
case PICKFILE_REQUEST_CODE: {
String path = new File(data.getData().getPath()).getAbsolutePath();
if (path != null) {
uri = data.getData();
path = FileUtils.getPath(getApplicationContext().getContentResolver(), uri);
name = path.substring(path.lastIndexOf("."));
extension = path.substring(path.lastIndexOf(".") + 1);
}
break;
}
}
}
getPath() 来自 FileUtils 类 (from this repo) 通过 URI 评估文件是哪种文件,但负责这种情况的是以下部分:
getPath() from FileUtils class (from this repo) evaluates the file via URI which kind of file it is, but responsible for that case is following part:
public static String getPath(final ContentResolver cr, final Uri uri) {
if (isDownloadsDocument(uri)) {
final String id = DocumentsContract.getDocumentId(uri);
final List<Uri> uris = new ArrayList<>();
uris.add(ContentUris.withAppendedId(
Uri.parse("content://downloads/public_downloads"), Long.valueOf(id)));
uris.add(ContentUris.withAppendedId(
Uri.parse("content://downloads/my_downloads"), Long.valueOf(id)));
uris.add(ContentUris.withAppendedId(
Uri.parse("content://downloads/all_downloads"), Long.valueOf(id)));
String res;
for (int i = 0; i < uris.size(); i++) {
res = getDataColumn(cr, uris.get(i), null, null);
if (res != null) return res;
}
}
}
getDataColumn()查询保存文件物理路径的文件列:
getDataColumn() queries the column of the file in which the physical path of the file is saved:
public static String getDataColumn(ContentResolver cr,
Uri uri, String selection,
String[] selectionArgs) {
Cursor cursor = null;
final String[] projection = {"_data"};
String col = "";
try {
cursor = cr.query(uri, projection, selection, selectionArgs,null);
if (cursor != null && cursor.moveToFirst()) {
final int column_index = cursor.getColumnIndexOrThrow("_data");
col = cursor.getString(column_index);
}
}finally{ if (cursor != null) cursor.close();}
return col;
}
当我测试它时,我得到的路径如下所示:E/AddItemActivity: result, path:/storage/emulated/0/Download/SampleVideo_176x144_1mb.3gp
.但在 Android 9 中,路径始终是空的.
When I'm testing the it the path I get looks for example like: E/AddItemActivity: result, path: /storage/emulated/0/Download/SampleVideo_176x144_1mb.3gp
.
But with Android 9 the path is always empty.
对于解决方案,我使用 MediaStore 来提取所选文件的名称和扩展名.所以我将 onActivityResult
中的代码替换为以下代码:
For the solution I am using the MediaStore to extract the name and extension of a choosen file. So I replace code in onActivityResult
with following code:
String path = new File(data.getData().getPath()).getAbsolutePath();
if(path != null){
uri = data.getData();
String filename;
Cursor cursor = getContentResolver().query(uri,null,null,null,null);
if(cursor == null) filename=uri.getPath();
else{
cursor.moveToFirst();
int idx = cursor.getColumnIndex(MediaStore.Files.FileColumns.DISPLAY_NAME);
filename = cursor.getString(idx);
cursor.close();
}
String name = filename.substring(0,filename.lastIndexOf("."));
String extension = filename.substring(filename.lastIndexOf(".")+1);
}
因此,使用 MediaStore.File.FileColumns.DISPLAY_NAME
可以从使用文件选择器选择的任何文件中获取文件名和扩展名.
So with MediaStore.File.FileColumns.DISPLAY_NAME
it's possible to get the file name and extension from any file choosen with a file chooser.
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