package com.example.photo;import androidx.appcompat.app.AppCompatActivity;import android.annotation.SuppressLint;import android.os.Bundle;import android.text.style.ClickableSpan;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends AppCompatActivity { final String TAG = MainActivity.class.getName(); private ImageView img; //声明一个ImageView对应界面中的图片框 private Button btnPre,btnNext; //声明两个按钮，对于上下翻页按钮 //四个图片资源 private int [] imgs = {R.drawable.img0,R.drawable.img1,R.drawable.img2,R.drawable.img3}; int index = 0; @SuppressLint("WrongViewCast") @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //获取xml中的控件存储到对象中 img = findViewById(R.id.img); btnPre = findViewById(R.id.btnPre); btnNext = findViewById(R.id.btnNext); //设置事件监听器 BtnClick btnClick = new BtnClick(); } public BtnClick implements View.OnClickListener{ }事件监听器一直标红，有大哥知道是啥情况吗}