ListView-无法使OnCheckedChangeListener(复选框)正常工作 [英] ListView - can't get OnCheckedChangeListener (Checkboxes) to work

问题描述

基于问题的演变，我编辑了这个问题.


所以问题是:我想用复选框填充ListView，并且要自定义ListView，所以我不使用simple_multiple_choice_mode，而是将布局放在list_item.xml中:(对于每一行)

Based on evolution of the problem, I edited this question.


So the problem is: I want to populate a ListView with checkboxes, and as I want to customize my ListView I''m not using simple_multiple_choice_mode, I''m putting my layout on list_item.xml: (for each row)

        <checkbox>
xmlns:android="http://schemas.android.com/apk/res/android" android:paddingLeft="8mm"
android:layout_width="fill_parent"
        android:layout_height="wrap_removed" android:id="@+id/nomeAPP" style="?listItem">
        </checkbox>

我的ListView位于lista.xml

My ListView is on lista.xml

<ListView android:id="@android:id/list"

        android:layout_width="fill_parent" android:layout_height="wrap_content"

        style="?whiteBackground">

</ListView>

我的适配器:

my adapter:

list=getListView();
            this.setListAdapter(new ArrayAdapter<String>(this,
                    R.layout.list_item, aux));

因此，我试图为复选框创建一个setOnCheckedChangeListener，以便将所选的项目存储在数组中.

所以我根据以下答案做了这个监听器:

So I''m trying to make a setOnCheckedChangeListener for the checkboxes, so I can store the chosed items in an array.

So I did this listener based on the answer below:

CheckBox cb = (CheckBox) findViewById(R.id.CheckBox01);
            cb.setOnCheckedChangeListener(new OnCheckedChangeListener() {

                public void onCheckedChanged(CompoundButton buttonView,
                        boolean isChecked) {
                    // TODO Auto-generated method stub
                    if (buttonView.isChecked()) {
                        Toast.makeText(getBaseContext(), "Checked",
                                Toast.LENGTH_SHORT).show();
                    }
                    else
                    {
                        Toast.makeText(getBaseContext(), "UnChecked",
                                Toast.LENGTH_SHORT).show();
                    }

                }
            });

问题是:我得到了NULL异常. CURIOUS 的事情是:如果我切换"布局以使用简单的

Problem is: I get the NULL exception. The CURIOUS thing is: if I "switch" my layout for a simple

<ScrollView android:id="@+id/widget54" android:layout_width="fill_parent"

android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android">

<LinearLayout android:orientation="vertical"

android:layout_width="fill_parent" android:layout_height="fill_parent">
<CheckBox android:text="Checkbox" android:id="@+id/CheckBox01"

android:layout_width="wrap_content" android:layout_height="wrap_content"></CheckBox>
</LinearLayout>

</ScrollView>

忘了我的ListView，它起作用了！那么，我的布局有什么问题?

我创建了一个新的小项目，目的只是为了让大家看到确切的情况.在此处 [

And forget my ListView, it works! So, what''s wrong with my layout?

I created a new little project just to let you guys see exactly the situation. It''s available here[^] Right now does not work, but if you uncomment the adapter, change ListActivity to Activity and change setContentView, it will work (checked/unchecked toast text).

Another curious thing I found is that with ListActivity does not work never.... wondering if it''s related...

推荐答案

我上次回答:http ://www.codeproject.com/Questions/253369/Problem-getting-Checkbox-items-on-the-ListView

这仍然是一个普遍的问题.

阅读该stackoverflow-thread的答案，您会发现:

I answered last time: http://www.codeproject.com/Questions/253369/Problem-getting-Checkbox-items-on-the-ListView

and it is still a common problem.

Read the answers of that stackoverflow-thread and you''ll find this:

private void addClickHandlerToCheckBox(CheckBox checkbox) {
    checkbox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
        public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
            CheckBox checkbox = (CheckBox)arg0; 
            boolean isChecked = checkbox.isChecked();
            // Store the boolean value somewhere durable
        }
    }
);

那么您可以访问持久存储"中存储的值.



您需要将侦听器添加到复选框-否则您将不知道哪个复选框已被选中.

then you can access the value that you have stored "somewhere durable".



You need to add the listener to the checkbox - otherwise you will not know which checkbox has been hit.

   // HashMap as member variable to store state of the checkboxes
   // needs to be final to be accessed in anonymous listener class
   // Don't be scared by the Key and Value, those work as fine as int and boolean
   private final HashMap<integer,> oMapCheckBoxSelection = new HashMap<integer,>;

   // ID's for the Checkboxes
   // store as variable to have a common reference
   private final static int
     iCheckBoxXY = 0,
     iCheckBoxXZ = 1;
{
   
   // ...

   CheckBox oCheckBoxXY = (CheckBox) findViewById(R.id.nomeAPP);
   oCheckBoxXY.setID();
   addClickHandlerToCheckBox(oCheckboxXY);


   // ....

   // Check if the checkbox is in the Hashmap and read it.
   if(oMapCheckBoxSelection.contains(iCheckBoxXY)){
     boolean isCheckboxSelected = oMapCheckBoxSelection.get(iCheckBoxXY);
   }


}

private void addClickHandlerToCheckBox(CheckBox checkbox) {
    checkbox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
        public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
            CheckBox checkbox = (CheckBox)arg0; 
            oMapCheckBoxSelection.put(checkbox.getID(), checkbox.isChecked());
        }
    }
);

问题是获取正确的初始化HashMap值，并在尝试读取该值之前验证它是否已初始化.
您还可以在初始化复选框时初始化HashMap值:
oMapCheckBoxSelection.put(oCheckBoxXY.getID(), oCheckBoxXY.isChecked());
...但是我想更喜欢使用HashMap.contains进行检查，以确保它是.

Problem is to get a proper initialized HashMap Value and to verify if it is initialized before you try to read that value.
You might also init the HashMap-Value when you init the Checkbox:
oMapCheckBoxSelection.put(oCheckBoxXY.getID(), oCheckBoxXY.isChecked());
...but I''d like to prefer the check with HashMap.contains to make sure it is.

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