Question

/*
this is the class which is called when a button is pressed in main activity. onResume is called along with onCreate first, and the list is getting populated with the last row input from the database multiple times.

目的是使用数据库中的表中的数据填充listview。何时被onResume调用？ * /

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

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

public class Expenses extends Activity {
    ListView l;Databasehelper mydb;List<ListViewItem> items;
    MyAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_expenses);
        l= (ListView)findViewById(R.id.lv1);
        mydb=new Databasehelper(this);
         items= new ArrayList<Expenses.ListViewItem>();


        //adapter= new MyAdapter(this, items);
        //l.setAdapter(adapter);
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        items.clear();
        ListViewItem a= new ListViewItem();
        Cursor cur=mydb.getData();
        if(cur.getCount()==0)
            Toast.makeText(this, "No expenses to display", Toast.LENGTH_LONG).show();

        cur.moveToFirst();
        do
        {
            a.category=cur.getString(0);
            a.status=cur.getString(1);
            a.amount=cur.getString(2);
            items.add(a);
        }while(cur.moveToNext());
        adapter= new MyAdapter(this, items);
        l.setAdapter(adapter);
        for(int i=0; i<items.size(); i++)
        {
            System.out.print(items.get(i).category+" "+items.get(i).status+" "+items.get(i).amount);
            System.out.println();
        }

    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.expenses, menu);
        return true;
    }

    public class ListViewItem{
        public String category, amount, status;
    }

    public void onAdd(View v){
        Intent in= new Intent(this, Input.class);
        startActivityForResult(in, 10);
    }

}

//请帮助填充表格。我怀疑恢复方法有问题。当我使用print命令打印时，列表包含相同//的多个副本。但是，数据库中的表包含正确的元组

Answer 1

问题是你做的循环。在迭代游标时，您使用相同的ListViewItem对象来设置值。您应该在游标的每次迭代中创建一个新的ListViewItem对象。像这样：

    do {
        ListViewItem a = new ListViewItem()
        a.category=cur.getString(0);
        a.status=cur.getString(1);
        a.amount=cur.getString(2);
        items.add(a);
    } while(cur.moveToNext());

ListView的整个大小的List都填充了相同的值

1 个答案: