Android click event color remains unchanged? Data binding lifecycle setting is key

In Android development, the problem of no change in color after clicking on UI elements is usually not a code error, but a problem with data binding or view update mechanism. This article analyzes a case and provides solutions.

Case: Developers use ViewModel and DataBinding to update the UI. HomeFragmentVM handles sorting logic and color calculations. The fragment_home.xml layout file uses TextView to display sorting options. Through data binding, the color value of HomeFragmentVM is applied to the textColor property of the TextView. The click event is bound to handleSort method through android:onclick property. The getSortTextColor method returns different color values ​​(color_333 or color_red_1) according to the sorting conditions, and handleSort method updates the ViewModel data. But the UI color remains unchanged.

The root of the problem: HomeFragment does not properly set the lifecycle owner of DataBinding. DataBindingUtil.inflate returns a ViewDataBinding object. You need to call setLifecycleOwner method to bind the life cycle of the Fragment or Activity to the object to ensure that the ViewModel data changes can correctly update the UI.

Solution: Add in the onCreateView method of HomeFragment:

 this.binding.setLifecycleOwner(this.getActivity());

This code binds the Activity to the binding object as the lifecycle owner. The DataBinding framework listens to ViewModel data changes, updates the UI color in time, and solves the problem of the color not changing after clicking. This code is missing, even if the ViewModel data changes, the UI will not be updated, resulting in the click event color change that cannot be displayed.

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