Dear yyqdian
after many years passed here and many questions asked permit me to suggest you to follow theese guidelines:
Try, when is possible, to show the minimum code necessary to reproduce the problem you are experiencing. Many times, doing this, you'll discover a 'type 0' problem (the problem does not exists). In other cases monks will have something to explain you or to work with.
Try to be less telegraphic in your descriptions and questions. Many monks here, and maybe we too, are not english native, so simple sentences and clear words are more easy worldwide understood.
If someone propose a solution, before reposting, try it and show the results of the test.
Hth
L*
There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.