错误“无法解析符号编辑文本"在 Android Studio MyFirstApp 教程中

我是 Android Studio 和 Android 开发的新手.所以我正在按照 developer.android.com 提供的教程进行操作，但在这一行中出现错误:EditText editText = (EditText) findViewById(R.id.editText);错误是说:找不到符号变量 editText .

I'm new to Android Studio and Android development. So I was following the tutorial given by developer.android.com and I'm having an error in this line : EditText editText = (EditText) findViewById(R.id.editText); The error is saying that : cannot find symbol variable editText .

这是我代码的一部分:

import android.os.Bundle;
import android.widget.EditText;


public class MainActivity extends AppCompatActivity {
   
    public void sendMessage(View view){
        EditText editText = (EditText) findViewById(R.id.editText);
        String message = editText.getText().toString();

    }
}