Backup/Restore SQLite db file to/from location outsides app's storage

I've successfully backup my .db file from file:///data/data/my.package.name/databases/data.db into file:///storage/sdcard0/data.db using fileEntry.copyTo(), but have problem on restore db file back to app. If I copy backup .db file to file:///android_asset/www/ I got FileError error code 1000, and if I copy the file to file:///data/data/my.package.name/databases/ directly, there is no error occurred, but my app still reading a empty database after restore done.

My restore db code:

function performDBRestore() {
  window.requestFileSystem(
      LocalFileSystem.PERSISTENT, 0,
      function(fileSystem) {
          window.resolveLocalFileSystemURL(
              "file:///storage/sdcard0/data.db",
              function(fileEntry) {
                  window.resolveLocalFileSystemURI(
                      "file:///data/data/my.package.name/databases/",
                      function(directoryEntry) {
                          fileEntry.copyTo(directoryEntry, "data.db",
                              function (fileEntry) {
                                  console.log("Restore success!");
                              },
                              function (error) { //no error, but db still empty while open
                                  console.log("Restore fail!");
                              }
                          );
                      },
                      function(error) {
                          //if I copy backup file to "file:///android_asset/www/", I got errCode 1000 here
                      }
                  );
              },
              function (error) {
                  //some error handling....
              }
          );
      },
      function(error) {
          //some error handling....
      }
  );

}

Any idea? thanks a lot.