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kotlinlang

SOLVED

I'm using Material. when I attached a click event, it shows error:     `java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.material.button.MaterialButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference`

```
submit_btn.setOnClickListener {
            this.findNavController().navigate(R.id.action_mainFragment_to_homeFragment)
        }
```

if I use null-safety, the button does nothing
```
submit_btn?.setOnClickListener {
            this.findNavController().navigate(R.id.action_mainFragment_to_homeFragment)
        }
```

SOLVED