android: showing a progress dialog

问题:

I have looked at the Android API and other posts here on stackoverflow, but have not been able to figure this out.

My app downloads files to the sd card. I would like to pop a "loading..." dialog while the file is downloading and then have it disappear when the download is finished. This is what i came up with using the android API:

ProgressDialog pd = ProgressDialog.show(this,"","Loading. Please wait...",true);

//download file

pd.cancel();

however the dialog doesn't actually show. when i debug it, it claims that it is showing, but it is obviously not on the screen.

what can i do?

回答1:

You have to run the download code into a separated Thread. The easy way is to use AsyncTask

Look also this article on how to use it

回答2:

I have a somewhat similar scenario, more of a level loading pause while stuff is being setup for a phase of a game. I launch the dialog, start level loading in a thread which is passed the context and call this at the end of the thread:

mContext.runOnUiThread(new Runnable(){
    public void run() {
        mContext.mProgressDialog.dismiss();
    }
});

I find the runOnUiThread() method extremely useful.