当我们在Android Java中通过扩展一个类来定义一个新的类时，如何改变类、字段类型和布局？

public class BaseActivity extends AppCompatActivity {
    // 基础类的代码
}

public class MyActivity extends BaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        // 添加或修改特定行为
    }
}

public class MyBaseClass {
    protected String myField;
}

public class MyDerivedClass extends MyBaseClass {
    private int myNewField;

    public int getMyNewField() {
        return myNewField;
    }

    public void setMyNewField(int myNewField) {
        this.myNewField = myNewField;
    }
}

public class MyBaseActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_base);
    }
}

public class MyNewActivity extends MyBaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_new); // 设置新的布局文件
    }
}