SAF DocumentFile -检查路径是否存在，而不在每个文件夹级别创建每个DocumentFile

Question

创建映像时，如果要检查"/folder/subfolder/subsubfolder/test/test.txt“文件是否存在，请执行以下操作：

DocumentFile sdCard = ...; // i have already retrieved the sd card root with the users help via SAF

String path = "<SD CARD>/folder/subfolder/subsubfolder/test/test.txt";
List<String> pathParts = Arrays.asList(path.split("/"));
DocumentFile doc = sdCard;
// go through all folders, starting at sd card, to check, if the desired file exists
for (int i = 1; i < pathParts.size(); i++)
{
    DocumentFile nextDoc = doc.findFile(pathParts.get(i));
    if (nextDoc != null)
        doc = nextDoc;
    else
    {
        doc = null;
        break;
    }
}

if (doc == null)
{
    // file does not exist
}
else
{
    // file does exist
}

这是非常慢的，有没有更快的方法至少检查文件是否存在于SD卡上？我不想仅仅为了检查路径是否存在而创建每个DocumentFile ...

Answer 1

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    Uri uri = data.getData();
    DocumentFile pickedDir = DocumentFile.fromTreeUri(MainActivity.this, uri);
    String id = DocumentsContract.getTreeDocumentId(uri); 

    /* id is :  "primary:namefolder" if user select a "namefolder" from internal storage. 
     or CABB-5641 if user select external storage,
    */

    id = id + "/folder/subfolder/subsubfolder/test/test.txt";  // your path,  you must to ensure is consistent with that chosen by the user,

    Uri childrenUri = DocumentsContract.buildDocumentUriUsingTree(uri,id);
    DocumentFile chhildfile = DocumentFile.fromSingleUri(MainActivity.this,childrenUri);

    if(chhildfile != null && chhildfile.exists()){
        Log.d("laporan file", "file ini ada");
    }
}

我不是专家，我不知道这是否能在大多数android上工作，但我已经在Android模拟器和华硕Zenfone 5中尝试过，希望这能有所帮助

Answer 2

你不能直接用

String Muri = uri.toString()；

然后对每个文件夹uri使用共享首选项，然后在需要时调用它。