Show a progress bar when an Activity is loading

Question

I have a ListActivity which launches another Activity based on the list selection. This second Activity needs to load a fair bit of data from the internet and as such there is a noticeable delay between when the user clicks on an item and when the Activity displays.

This is a problem because I currently have no way to indicate to the user that their click is being processed (even just changing the colour of the selected list item would be sufficient but I can't find a good way to do that). Ideally I'd be able to display an indeterminate ProgressDialog while the second Activity is loading.

I've tried a few different approaches for this but nothing seems to work as desired.

---

I've tried the following:

• Retrieving the serializable data (not all of it but some part) in an AsyncTask in the first Activity and passing it as an extra to the second. This didn't really work well as a ProgressDialog I created in onPreExecute() didn't display immediately (it seems delayed by the processing done in doInBackground() for some reason.)

Here is the code for that:

AsyncTask<String, Void, String> read = new AsyncTask<String, Void, String>() {
    Dialog progress;

    @Override
    protected void onPreExecute() {
        progress = ProgressDialog.show(SearchActivity.this, 
                "Loading data", "Please wait...");
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        DatasetReader reader = new DatasetReader();
        reader.setFundID(params[0]);
        reader.addDatsets(FundProfile.datasets);
        reader.populate();
        return reader.toString();
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        progress.dismiss();
    }
};
read.execute(selectedItem.getUniqueID());
try {
    action = new Intent(SearchActivity.this, FundProfile.class);
    action.putExtra("data", read.get());
} catch(Exception ex) {
    ex.printStackTrace();
}

• In the second Activity's onCreate() method (this does not work at all):

  requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
  setProgressBarVisibility(true);

Here is the onCreate() method for the second approach:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setTitleColor(Color.WHITE);
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    setProgressBarVisibility(true);

    try {
        setContentView(R.layout.fund_profile);
        // init some data
        setProgressBarVisibility(false);
    } catch(Exception ex) {
        FundProfile.this.finish();
    }
}

Eternal

Which different approaches have you tried? Could you share your attempts? – Embalm

I'm surprised the first approach didn't work. A ProgressDialog shown in onPreExecute() should not be held up by the code in doInBackground(), perhaps there was some other issue with your code? – Punchboard

Possibly? I added the relevant code.. – Eternal

Answer 1

If you have long operations you should not be doing them in onCreate in any case as this will freeze the UI (whether or not the activity is displayed). The UI set by onCreate will not appear and the UI will be unresponsive until after the onCreate call finishes.

It seems you can start your second activity and display a progress bar (or requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);), then start an ASyncTask which will be responsible for updating your UI once data has been retrieved.

Biparty

Yeah, I figured that's the proper way to do it (load data in another thread), but I wanted to avoid it for now.. but I bit the bullet and did it this way (AsyncTask makes this less painful than it could have been..) – Eternal

Answer 2

Adam,

It sounds like you are looking for the Indeterminate Progress bar: http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/ProgressBar2.html

You can display this while you are loading your second Activity then set the visibility to false once the second Activity has loaded its data.

Anticlinal

The first activity's view stays on the screen until the entire onCreate() method completes, so I never see a progress bar. – Eternal

when are you calling setContentView() in your onCreate() method? – Anticlinal

First thing after (supposedly?) showing the progress bar. I've updated the original post with this info. – Eternal

well, it looks like your setting the progress bar to visible then immediately after setting it back to invisible. – Anticlinal

I commented out some code which retrieves the data and populates the views (actually, I created some custom views which populate their own data..) – Eternal

Answer 3

Move creating the Intent -- and really anything you need to do after the AsyncTask completes -- into onPostExecute:

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    progress.dismiss();
    Intent action = new Intent(SearchActivity.this, FundProfile.class);
    action.putExtra("data", result);
    // ... do more here
}

The problem is that AsyncTask.get() blocks until the task is completed. So in the code above, the UI thread is blocked and the ProgressDialog is never given a chance to appear until the task completes.

Hermann