java - 当用户开始输入时如何监听？

Question

我正在使用 android studio 和 fire-base 设计一个聊天应用程序，并了解如何创建一个监听器，就像用户在编辑文本字段中输入一样，fire-base 上的用户值将更改为 true当用户没有输入时，该值将变为 false。？我寻找这个解决方案大约一周了，但没有找到任何关于我的研究的答案。

如何放置TextWatcher？

public class MainActivity extends AppCompatActivity{


private EditText editText;
private ListView listView;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    counter = 0;
    Firebase.setAndroidContext(this);
    final Firebase firebase = new Firebase("https://samp-is.firebaseio.com/");


    editText = (EditText) findViewById(R.id.editText);
    listView = (ListView) findViewById(R.id.listView);

    listView.setAdapter(new MessageAdapter(this, Message.class, R.layout.fragment_message, firebase.child("chat")));

    Button button = (Button) findViewById(R.id.button);

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            counter++;

            Message message = new Message();

            message.setMessage(editText.getText().toString());
            editText.setText("");
            message.setAuthor("Name");
            message.setCounter(counter);
            firebase.child("chat").push().setValue(message);


        }
        });
    }
}

Answer 1

您是否在寻找onTextChanged(CharSequence s, int start, int before, int count)？

引自TextWatcher

This method is called to notify you that, within s, the count characters beginning at start have just replaced old text that had length before.

此事件将触发用户在 EditText 中输入内容。