Android List.add函数覆盖以前的条目

时间：2015-08-16 19:05:16

标签： android listview

我尝试使用以下代码使用数据库查询的结果填充列表。

public List<Entry> getAllEntries() {
    List<Entry> entries = new ArrayList<>();
    Cursor cursor = database.query(SQLiteHelper.TABLE_CLIENTS, allColumns, null, null, null, null, null);
    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
      Entry entry = cursorToEntry(cursor);
      entries.add(entry);
        Log.v("andy", "Entry:::   " + entry.toString());
        Log.v("andy","Entries::: " + entries.toString());
      cursor.moveToNext();
    }
    cursor.close();
    return entries;
  }

以下是运行以下内容时输出的内容

List<Entry> e = getAllEntries();



08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entry:::   ID: 1 / Name: andy / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entries::: [ID: 1 / Name: andy / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0]
08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entry:::   ID: 2 / Name: cg1 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entries::: [ID: 2 / Name: cg1 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0, ID: 2 / Name: cg1 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0]
08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entry:::   ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 19:53:28.274  13698-13698/uk.co.ab.ci V/andy﹕ Entries::: [ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0, ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0, ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0]

EDIT :: 改变

Log.v("andy","Entries::: " + entries.toString());

to 

Log.v("andy","Entries::: " + entries.get(0));

also adding:

Log.v("andy","Entries size::: " + entries.size());

outputs:

08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entry:::   ID: 1 / Name: andy / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries::: ID: 1 / Name: andy / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries size::: 1
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entry:::   ID: 2 / Name: cg1 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries::: ID: 2 / Name: cg1 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries size::: 2
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entry:::   ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries::: ID: 3 / Name: yjh / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:33:06.054  30909-30909/uk.co.ab.ci V/andy﹕ Entries size::: 3

编辑* 2：进一步记录测试

将功能更改为：

public List<Entry> getAllEntries() {
      Log.v("andy","getallentries");
    List<Entry> entries = new ArrayList<Entry>();
    Cursor cursor = database.query(SQLiteHelper.TABLE_CLIENTS, allColumns, null, null, null, null, null);
    cursor.moveToFirst();
    int i = 0;
    while (!cursor.isAfterLast()) {
        i++;
        Entry entry = cursorToEntry(cursor);
        Log.v("andy", "Entry:::   " + entry.toString());
        entries.add(new Entry(i, "testlistitemname"+i, null, null, null, null, null, null, null, null, 0, 0));
      cursor.moveToNext();
    }
    Log.v("andy","Entries 0::: " + entries.get(0));
    Log.v("andy","Entries 1::: " + entries.get(1));
    Log.v("andy","Entries 2::: " + entries.get(2));
    Log.v("andy","Entries size::: " + entries.size());
    cursor.close();
    return entries;
  }

outputs :

08-16 20:51:03.184    6357-6357/uk.co.ab.ci V/andy﹕ Entries 0::: ID: 3 / Name: testlistitemname3 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:51:03.184    6357-6357/uk.co.ab.ci V/andy﹕ Entries 1::: ID: 3 / Name: testlistitemname3 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:51:03.184    6357-6357/uk.co.ab.ci V/andy﹕ Entries 2::: ID: 3 / Name: testlistitemname3 / Address 1: null / Address 2: null / Address 3: null / Postcode: null / Tel: null / Mob: null / Email: null / Website: null / deleted: 0
08-16 20:51:03.184    6357-6357/uk.co.ab.ci V/andy﹕ Entries size::: 3

为什么新条目总是覆盖所有以前添加的条目？我无法弄清楚如何使代码变得更简单，以弄清楚什么是错误的。

感谢任何帮助！

2 个答案:

答案 0 :(得分：0)

如果您正确地看到日志，则新条目不会覆盖所有先前添加的条目。它只是添加了一个新条目。

你的循环在这里运行了3次

Log.v("andy","Entries::: " + entries.toString());

首次打印项目列表1，第二次打印时间为3秒。

第一次

  

条目::: [ID：1 /名称：andy /地址1：null /地址2：null /   地址3：null / Postcode：null / Tel：null / Mob：null / Email：null   /网站：null / deleted：0]

第二次

  

条目::: [ID：2 /名称：cg1 /地址1：null /地址2：null /   地址3：null / Postcode：null / Tel：null / Mob：null / Email：null   /网站：null / deleted：0，ID：2 /名称：cg1 /地址1：null /   地址2：null /地址3：null / Postcode：null / Tel：null / Mob：   null / Email：null / Website：null / deleted：0]

第3次

  

条目::: [ID：3 /名称：yjh /地址1：null /地址2：null /   地址3：null / Postcode：null / Tel：null / Mob：null / Email：null   /网站：null /删除：0，ID：3 /名称：yjh /地址1：null /   地址2：null /地址3：null / Postcode：null / Tel：null / Mob：   null / Email：null / Website：null / deleted：0，ID：3 / Name：yjh /   地址1：null /地址2：null /地址3：null / Postcode：null /   电话：null / Mob：null /电子邮件：null /网站：null / deleted：0]

请正确查看日志。

答案 1 :(得分：0)

事实证明，这是因为我将所有的Entry类变量设置为静态，我学到的将使它们在类的所有实例中都相同。所以这就是覆盖以前的条目。

只是让其他人有这个问题！

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