关于 Android ListView 和 ArrayAdapter 的问题

发布于 2024-11-03 01:33:16 字数 874 浏览 15 评论 0原文

所以我在这里玩弄这段代码，主要目标是单击按钮后用新项目更新列表。我的代码可以工作，但我不确定这是否是正确的方法。

我有两个方法。第一个方法采用我的 ArrayList，添加两个字符串并将其发布到列表视图。伟大的！

当我点击按钮时，会调用我的第二种方法。它添加了一个新字符串并更新了列表，但为了让我更新现有的列表视图，我必须再次执行“setListAdapter(new ArrayAdapter....”行，我不确定这是否正确我可以使用一些输入，

谢谢！

方法 1：

static final List list = new ArrayList();
private void showEvents (Cursor cursor){
        list.add("foo");
        list.add("bar");
        Log.d(TAG,"showevent");
        setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));



    }

方法 2（当我点击 listView 下的按钮时调用此方法）：

private void updateListView(){
        try{
            list.add("son");
            setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));


        }catch (Exception e){
            Log.d(TAG, "E="+e);
        }
    }

原文

So I'm toying with this code here, and the main objective is to update a list with a new item once I click a button. The code I have works, but I'm not sure if it's the right way to do it.

I have two methods. The first method takes my ArrayList, add's two strings and posts it to the listview. Great!

The Second method I have is called when I tap on a button. It add's a new string and updates the list, but in order for me to update the existing listview, I had to do the "setListAdapter(new ArrayAdapter...." line again and I'm not sure if that's the right thing to do.

I can use some input please, thanks!

Method 1:

static final List list = new ArrayList();
private void showEvents (Cursor cursor){
        list.add("foo");
        list.add("bar");
        Log.d(TAG,"showevent");
        setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));



    }

Method 2 (this is called when I tap a button that is under the listView):

private void updateListView(){
        try{
            list.add("son");
            setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));


        }catch (Exception e){
            Log.d(TAG, "E="+e);
        }
    }

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蘑菇王子 2024-11-10 01:33:16

无需再次设置列表适配器，而是在 ArrayAdapter 上调用 notificationDataSetChanged()。上面的代码将“起作用”，但它会强制整个 ListView 重新绘制，因此如果您有一个很长的列表并且用户已经滚动，它会将它们弹出到顶部。通知是一种更干净的方法。

非常简单的代码。在这种情况下，我在活动中引用了数组适配器：

adapter.notifyDataSetChanged();

这是基于您的代码的示例：

static final List list = new ArrayList();
ArrayAdapter adapter;

private void showEvents (Cursor cursor){
    list.add("foo");
    list.add("bar");
    Log.d(TAG,"showevent");

    adapter = new ArrayAdapter<String>(this, R.layout.singleitem, list)
    setListAdapter(adapter);
}

private void updateListView(){
    try{
        list.add("son");
        adapter.nofityDataSetChanged();
        // not needed anymore
        //setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));
    }catch (Exception e){
        Log.d(TAG, "E="+e);
    }
}

Rather than setting the list adapter again, call the notifyDataSetChanged() on the ArrayAdapter. The above will "work", but it forces the entire ListView to redraw, so if you have a long list and the user has scrolled it'll pop them back to the top. The notify is a cleaner way to do that.

Very simple code. I've got a reference to the array adapter in the activity in this case:

adapter.notifyDataSetChanged();

Here's and example based on your code:

static final List list = new ArrayList();
ArrayAdapter adapter;

private void showEvents (Cursor cursor){
    list.add("foo");
    list.add("bar");
    Log.d(TAG,"showevent");

    adapter = new ArrayAdapter<String>(this, R.layout.singleitem, list)
    setListAdapter(adapter);
}

private void updateListView(){
    try{
        list.add("son");
        adapter.nofityDataSetChanged();
        // not needed anymore
        //setListAdapter(new ArrayAdapter<String>(this, R.layout.singleitem, list));
    }catch (Exception e){
        Log.d(TAG, "E="+e);
    }
}

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过度放纵 2024-11-10 01:33:16

为 ArrayAdapter 声明一个成员变量（例如 myAdapter），然后在 showEvents 方法中初始化它并将其设置为 listView。将字符串添加到列表后，在 updateListView 方法中，只需调用 myAdapter.notifyDataSetChanged(); 即可解决问题