如何使用按钮onClick从ListView中删除所有内容？

Question

如何使用按钮onClick从ListView中删除所有内容？当我尝试“fullCourseList.clear（）；”时，我无法添加更多课程，只有再次访问页面后，页面才会刷新

import static com.example.diplom.MainActivity.fullCourseList;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.example.diplom.model.Course;
import com.example.diplom.model.Order;

import java.util.ArrayList;
import java.util.List;

public class OrderPage extends AppCompatActivity {

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

        ListView orders_list = findViewById(R.id.orders_list);

        List<String> coursesTitle = new ArrayList<>();
        for (Course c : MainActivity.fullCourseList) {
            if(Order.items_id.contains(c.getId()))
                coursesTitle.add(c.getTitle());

        }

        orders_list.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, coursesTitle));


    }

    public void openMain(View view){
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        startActivity(intent);
    }
    public void onClick(View v) {
        //fullCourseList.clear();
    }
}

Answer 1

清除ArrayList后，必须通知适配器数据源已更改。

public class OrderPage extends AppCompatActivity {
    
    private ListView orders_list;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_order_page);
        orders_list = findViewById(R.id.orders_list);
        List<String> coursesTitle = new ArrayList<>();
        for (Course c : MainActivity.fullCourseList) {
            if(Order.items_id.contains(c.getId()))
                coursesTitle.add(c.getTitle());
        }
        orders_list.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, coursesTitle));
    }

    public void openMain(View view){
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        startActivity(intent);
    }
    public void onClick(View v) {
        fullCourseList.clear();
        orders_list.notifyDataSetChanged();
    }
}