如何在编辑片段的编辑文本时通知活动（Android）？

Question

I have an edittext in one of my fragments. I also have a String field in my activity that starts the fragment, and every time the text changes in the edittext, I want to change the string in my activity accordingly but I'm not sure how to do that.

Answer 1

1. Create an interface like this

   interface OnDataChangeListener { fun onChange(string: String) }

2. In your fragment's constructor pass an instance of this interface as a parameter

   class MyFragment(val onDataChangeListener: OnDataChangeListener): Fragment

3. Now when the text changes in the edit text, call this interface's method

   editText.addTextChangedListener(object : TextWatcher{ override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) { } override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) { } override fun afterTextChanged(s: Editable?) { onDataChangeListener.onChange(s.toString()) } })

4. Now implement this interface in our activity

   class MainActivity : AppCompatActivity(), OnDataChangeListener { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) AppUtils.addFragment(this, MyFragment(this), R.id.fragment_container) } override fun onChange(string: String) { val textView = findViewById<TextView>(R.id.textView) textView.text = string } }

That's it. This should give you the required output.

Answer 2

Create an interface that the Activity implements and pass it to your Fragment . Then, add a TextWatcher to the EditText with editText.addTextWatcher() inside your Fragment , and notify the listener inside onTextChanged . This approach is based off the Android Docs .