Handling ProgressBars

Overview

ProgressBar is used to display the progress of an activity while the user is waiting. You can display an indeterminate progress (spinning wheel) or result-based progress.

Indeterminate

We can display an indeterminate progress bar which we show to indicate waiting:

<ProgressBar
  android:id="@+id/pbLoading"
  android:visibility="invisible"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content" />

and then manage the visibility in the activity:

// on some click or some loading we need to wait for...
ProgressBar pb = (ProgressBar) findViewById(R.id.pbLoading);
pb.setVisibility(ProgressBar.VISIBLE);
// run a background job and once complete
pb.setVisibility(ProgressBar.INVISIBLE);

Typically you want to try to put the ProgressBar in the place where data is going to show (i.e. as a placeholder for an image). For a ListView, you put the ProgressBar in the header or footer, which lets you put an arbitrary layout outside of the adapter.

Result-based

ProgressBar can be used to report the progress of a long-running AsyncTask. In this case:

• ProgressBar can report numerical results for a task.
• Must specify horizontal style and result max value.
• Must publishProgress(value) in your AsyncTask

<ProgressBar
  android:id="@+id/progressBar1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:visibility="invisible"
  style="?android:attr/progressBarStyleHorizontal"
  android:max="100" />

and then within the AsyncTask:

public class DelayTask extends AsyncTask<Void, Integer, String> {
	int count = 0;
	@Override
	protected void onPreExecute() {
	  pb.setVisibility(ProgressBar.VISIBLE);
	}

	@Override
	protected String doInBackground(Void... params) {
		while (count < 5) {
			SystemClock.sleep(1000); count++;
			publishProgress(count * 20);
		}
		return "Complete";
	}

	@Override
	protected void onProgressUpdate(Integer... values) {
		 pb.setProgress(values[0]);
	}
	
}

and using this pattern any background tasks can be reflected by an on-screen progress report.

ActionBar Progress Bar

Note: with API 21 and the latest support v7 library, the actionbar progress bar has been deprecated in favor of using the Toolbar.

The ActionBar has built-in progress bar UIs for both indeterminate and result-based progress bars. To show an indeterminate progress bar on the ActionBar simply requires setProgressBarIndeterminateVisibility:

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // MUST request the feature before setting content view
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); 
        setContentView(R.layout.activity_main);
    }
    
    // Should be called manually when an async task has started
    public void showProgressBar() {
        setProgressBarIndeterminateVisibility(true); 
    }
    
    // Should be called when an async task has finished
    public void hideProgressBar() {
    	setProgressBarIndeterminateVisibility(false); 
    }
}

There are support versions of these as well:

supportRequestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setSupportProgressBarIndeterminateVisibility(boolVal);

Note that for this to work, you must call requestWindowFeature as shown above before setContentView in onCreate. You can also use a result-based progress bar displayed in the ActionBar as well:

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // MUST request the feature before setting content view
        requestWindowFeature(Window.FEATURE_PROGRESS); 
        setContentView(R.layout.activity_main);
    }
    
    // Should be called manually when an async task has started
    public void showProgressBar() {
        setProgressBarVisibility(true);
    }

    public void updateProgressValue(int value) {
        // Manage the progress (i.e within an AsyncTask)
        // Valid ranges are from 0 to 10000 (both inclusive). 
        // If 10000 is given, the progress bar will be completely filled and will fade out.
        setProgress(value);
    }
    
    // Should be called when an async task has finished
    public void hideProgressBar() {
    	setProgressBarVisibility(false);
    }
}

Note that for this to work, you must call requestWindowFeature as shown above before setContentView in onCreate.

Note: with API 21 and the latest support v7 library, the actionbar progress bar has been deprecated in favor of using the Toolbar.

References

• http://developer.android.com/reference/android/widget/ProgressBar.html
• http://www.mkyong.com/android/android-progress-bar-example/
• Activity ProgressBar