Why createFile() method can not create file

My development platform is Android 5.0.2, and I followed API document of $cordovaFile carefully, the following is my code snippet:

$cordovaFile.createFile(cordova.file.dataDirectory, "test.txt", true)
.then(function (success) {
console.log('OK');
}, function (error) {
console.log(error.code)
});

In fact, I got 'OK', but I can't find file test.txt in foler files. Can anybody help me? Thanks a lot in advance.