我对android工作室和java都是新手。我想知道为什么我不能在模型类中使用“this”。我得到以下错误消息：“不兼容的类型：模型不能转换为上下文”。如果我在notes类中编写代码，它就可以正常工作。错误出现在模型中（在我创建按钮的地方，androidstudio中“this”用红色下划线）。

package com.example.notesapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

public class Notes extends AppCompatActivity implements View.OnClickListener {

    private Controller controller;

    private EditText etNotesCreationHeader;
    private EditText etNotesCreationText;
    private Button btnNotesCreate;
    private Button btnNotesCreationCreate;
    private TextView tvNotesHeader;
    private TextView tvNotesCounter;

    public int counter;

    // נגדיר משתנה מסוג SharedPreferences
    private SharedPreferences sharedPref;
    // כדי לכתוב ל Shared Preferences נגדיר Editor שלו
    private SharedPreferences.Editor editor;

    private Intent intent;

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

        sharedPref = this.getSharedPreferences(String.valueOf(R.string.shared_preferences_file_name), MODE_PRIVATE);
        editor = sharedPref.edit();

        initViews();

        Intent intent = getIntent();
        String name = intent.getStringExtra("name");

        tvNotesHeader.setText("Welcome back, " + name + "!");
        tvNotesCounter.setText("Number of Notes: " + sharedPref.getInt("counter", 0));

        counter = sharedPref.getInt("counter", -1);

    }

    private void initViews() {
        tvNotesHeader = findViewById(R.id.tvNotesHeader);
        tvNotesCounter = findViewById(R.id.tvNotesCounter);
        btnNotesCreate = findViewById(R.id.btnNotesCreate);
        etNotesCreationHeader = findViewById(R.id.etNotesCreationHeader);
        etNotesCreationText = findViewById(R.id.etNotesCreationText);
        btnNotesCreationCreate = findViewById(R.id.btnNotesCreationCreate);

        btnNotesCreate.setOnClickListener(this);
        btnNotesCreationCreate.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view == btnNotesCreate) {
            etNotesCreationHeader.setVisibility(view.VISIBLE);
            etNotesCreationText.setVisibility(view.VISIBLE);
            btnNotesCreationCreate.setVisibility(view.VISIBLE);
            Toast.makeText(this, "Click 'Create' to finish!", Toast.LENGTH_SHORT).show();
        }

        if (view == btnNotesCreationCreate) {
            if ((etNotesCreationText.getText().toString().trim().equals("")) || etNotesCreationHeader.getText().toString().trim().equals("")) {
                Toast.makeText(this, "Please fill the fields!", Toast.LENGTH_SHORT).show();
            } else {
                //קטע יצירת הפתקים!
                etNotesCreationHeader.setVisibility(view.INVISIBLE);
                etNotesCreationText.setVisibility(view.INVISIBLE);
                btnNotesCreationCreate.setVisibility(view.INVISIBLE);
                //Toast.makeText(this, "The Note was created!", Toast.LENGTH_SHORT).show();

                etNotesCreationHeader.setText("");
                etNotesCreationText.setText("");

                if (-1 == sharedPref.getInt("counter", -1)) {
                    counter = 0;
                    editor.putInt("counter", counter);
                    editor.commit();
                } else {
                    counter += 1;
                    editor.putInt("counter", counter);
                    editor.commit();
                    tvNotesCounter.setText("Number of Notes: " + String.valueOf(sharedPref.getInt("counter", 0)));

                    this.controller.createNote();
                }
            }

            //כאן צריך להוסיף counter כדי שיוסיך ל-id של כל note מספר שונה, ובכך נשיג id ייחודי לכל note. בנוסף צריך להוסיף את ה-counter ל-shared preferences כדי שהוא תמיד יזכר על המכשיר ותמיד רק יגדל. ניתן להתשמש ב-id גם כשם במסמך של ה-shared preferences!
        }
    }
}

控制器：

package com.example.notesapplication;

public class Controller
{
    private Model model;

    public Controller() {
        this.model = new Model();
    }

    public void createNote() { this.model.createNote(); }
}

型号：

package com.example.notesapplication;

import android.app.Activity;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;

public class Model {
    public void createNote() {
        Button myButton = new Button(this);
    }
}