package com.example.myapplication;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;

import com.example.myapplication.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
    ActivityMainBinding binding;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(MainActivity.this,String.valueOf(StringUtils.num),Toast.LENGTH_SHORT).show();
            }
        });

    }
}

布局：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <import type="com.example.myapplication.StringUtils"/>
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <EditText
            android:id="@+id/three"
            android:layout_width="100dp"
            android:layout_height="40dp"
            android:layout_marginTop="100dp"
            android:text="@={StringUtils.getString(StringUtils.num)}"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/button"
            android:layout_width="100dp"
            android:layout_height="40dp"
            android:layout_marginTop="100dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/three" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

實(shí)際開發(fā)中使用viewmodel，這里用Stringutils,簡(jiǎn)單替代：一樣的原理偷办。

package com.example.myapplication;

import androidx.databinding.InverseMethod;

public class StringUtils {
    public static int num;
    @InverseMethod("getCode")
    public static String getString(int code) {
        if (code == 1) {
            return "第一";
        } else if (code == 2) {
            return "第二";
        } else {
            return "未知";
        }

    }
    public static int getCode(String name){
        if (name.equals("第一")){
            return 1;
        }else if (name.equals("第二")){
            return 2;
        }else {
            return 0;
        }
    }
}