Prevent Android Activity from Operating while using Bottom Sheet in PSLab App

This blog demonstrates how to prevent the Android Activity in the background from operating while the Bottom Sheet is up in the foreground. The demonstration will be purely from the work I have done under PR #1355 in PSLab Android repository.

Why prevent the Activity from operating?

When using Bottom Sheet in Android, it is preferable to dim the screen behind the Bottom Sheet to provide a good user experience. But the dimming of the screen is itself an indication that the screen won’t work. Also, if the Bottom Sheet is open and while sliding it, if, by mistake, any button in the background of the bottom sheet gets pressed, then if the function related to that button starts executing then it can create a bad user experience.

For example, in PSLab Android app, in Accelerometer instrument, there are record/pause and delete buttons in the toolbar as shown in figure 1. Now, if the bottom sheet is opened and while closing it if the delete button is by mistake pressed by the user, then whole recorded data gets deleted. Thus, it’s a good practice to prevent the background Activity from operating while Bottom Sheet is opened.

Figure 1. Accelerometer Instrument in PSLab Android app

How to prevent the Activity from operating?

In this demonstration, I will use the method followed by PSLab Android app in creating a Bottom Sheet and making the background dim using a View widget. A step by step guide on how to make a Bottom Sheet as in PSLab Android app can be found in [1] and [2].

Strategy

The strategy used in solving this problem is setting an OnClickListener to the View that is used to dim the background and close the Bottom Sheet (if open) and hide the View as soon as the method is called. The View is again made visible when an upward slide gesture is made to open the Bottom Sheet.

Follow the below steps to get the desired results:

  • First, in OnCreate() method, set the OnTouchListener to the view.
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
                              if(bottomSheetBehavior.getState()==BottomSheetBehavior.STATE_EXPANDED)
                    bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
tvShadow.setVisibility(View.GONE);
      }
});
  • Now, override the OnSlide() method of the GestureDetector class and add the following code to it.
@Override
public void onSlide(@NonNull View bottomSheet, float slideOffset) {
    Float value = (float) MathUtils.map((double) slideOffset, 0.0, 1.0, 0.0, 0.8);
    view.setVisibility(View.VISIBLE);
    view.setAlpha(value);
   }

So, now test the Bottom Sheet and you will find that the Bottom Sheet will get closed as soon as the click is made outside it if it is opened. The demonstration of the working of the above code is shown in figure 2.

Figure 2. Demonstration of preventing the background Activity from operating while Bottom Sheet is up

Resources

  1. http://thetechnocafe.com/make-bottom-sheet-android/: Blog on how to make a Bottom Sheet in Android