在片段中使用列表视图
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【中文标题】在片段中使用列表视图【英文标题】：Using list view in fragments 【发布时间】：2015-06-05 20:39:32 【问题描述】：我有一个抽屉布局片段（在主活动中），它显示一个可扩展列表，当我单击扩展项目的子项目时，会出现一个弹出窗口。这个带有自定义布局的弹出窗口包含文本视图、一个列表视图和 2 个按钮。
我为列表视图提供了 id：android:id="@android:id/list"，并从 onCreateView 函数中的 ViewGroup 返回 null，如下所示：
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
View rootView = inflater.inflate(R.layout.fragment_settings, null);
并使类扩展 Fragment 而不是 ListFragment
我执行了前 3 个步骤以避免“内容具有 id 属性为 'android.R.id.list' 的视图不是 ListFragment 中的 ListView 类”错误
但我仍然有指向
的 NullPointerException 错误failListView.setAdapter(adapter);
当点击“故障安全设置”项时
我看到了一些建议，但都没有用，比如 rootView .findViewById?() 不是 getActivity().findViewById() ==> 我已经这样做了。 或在 onCreateView 函数之前声明列表视图。 我真的很生气，我尝试了很多与其他人合作的建议。
尽管如此，我已经尝试将此 sn-p 添加到 onActivityCreated 函数中
TestFailsafeAdapter adapter = new TestFailsafeAdapter(getActivity().getApplicationContext(),
R.layout.dialog,R.id.textView1,
getResources().getStringArray(R.array.failsafe_list));
failListView.setAdapter(adapter);
任何帮助将不胜感激。
以下是弹出窗口中使用的自定义布局（dialog.xml）：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_
android:layout_ >
<LinearLayout
android:id="@+id/headers_container"
android:layout_
android:layout_
android:layout_marginTop="5dp"
android:orientation="horizontal" >
<TextView
android:id="@+id/textView1"
android:layout_
android:layout_
android:text="FailSafe"
android:textSize="16sp" />
<TextView
android:id="@+id/textView2"
android:layout_
android:layout_
android:layout_toRightOf="@+id/textView1"
android:text="On"
android:textSize="16sp" />
</LinearLayout>
<ListView
android:id="@android:id/list"
android:layout_
android:layout_
android:layout_alignParentLeft="true"
android:layout_below="@+id/headers_container"
android:background="#ffeeaa" >
</ListView>
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_
android:layout_
android:gravity="center"
android:layout_below="@android:id/list"
android:orientation="horizontal" >
<Button
android:id="@+id/dialogButtonReset"
android:layout_
android:layout_
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:text="Reset" />
<Button
android:id="@+id/dialogButtonSend"
android:layout_
android:layout_
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:text="Send" />
</LinearLayout>
</RelativeLayout>
以下是具有可绘制布局的可展开列表的片段（SettingsFragment.java）：
public class SettingsFragment extends Fragment
ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
int position = 0;
ListView failListView = null;
public SettingsFragment()
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
// View rootView = inflater.inflate(R.layout.fragment_settings, container, false);
View rootView = inflater.inflate(R.layout.fragment_settings, null);
failListView = (ListView) rootView.findViewById(android.R.id.list);
TestFailsafeAdapter adapter = new TestFailsafeAdapter(getActivity().getApplicationContext(),
R.layout.dialog,R.id.textView1, getResources().getStringArray(R.array.failsafe_list));
failListView.setAdapter(adapter);
return rootView;
@Override
public void onActivityCreated(Bundle savedInstanceState)
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
// get the listview
expListView = (ExpandableListView) getActivity().findViewById(R.id.lvExp);
// preparing list data
prepareListData();
listAdapter = new ExpandableListAdapter(getActivity(), listDataHeader, listDataChild);
// setting list adapter
expListView.setAdapter(listAdapter);
// Listview Group click listener
expListView.setOnGroupClickListener(new OnGroupClickListener()
public boolean onGroupClick(ExpandableListView parent, View v,
int groupPosition, long id)
return false;
);
// Listview Group expanded listener
expListView.setOnGroupExpandListener(new OnGroupExpandListener()
@Override
public void onGroupExpand(int groupPosition)
Toast.makeText(getActivity(),
listDataHeader.get(groupPosition) + " Expanded",
Toast.LENGTH_SHORT).show();
);
// Listview Group collasped listener
expListView.setOnGroupCollapseListener(new OnGroupCollapseListener()
@Override
public void onGroupCollapse(int groupPosition)
Toast.makeText(getActivity(),
listDataHeader.get(groupPosition) + " Collapsed",
Toast.LENGTH_SHORT).show();
);
// Listview on child click listener
expListView.setOnChildClickListener(new OnChildClickListener()
@Override
public boolean onChildClick(ExpandableListView parent, View v,
final int groupPosition, final int childPosition, long id)
// TODO Auto-generated method stub
if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equals("USB") )
FragmentManager manager = getFragmentManager();
/** Instantiating the DialogFragment class */
AlertDialogRadio alert = new AlertDialogRadio();
/** Creating a bundle object to store the selected item's index */
Bundle b = new Bundle();
/** Storing the selected item's index in the bundle object */
b.putInt("position", position);
/** Setting the bundle object to the dialog fragment object */
alert.setArguments(b);
/** Creating the dialog fragment object, which will in turn open the alert dialog window */
alert.show(manager, "alert_dialog_radio");
if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equals("Failsafe Setup") )
Toast.makeText(getActivity()," Failsafe Setup",Toast.LENGTH_SHORT).show();
// create a Dialog component
final Dialog dialog = new Dialog(getActivity());
//tell the Dialog to use the dialog.xml as it's layout description
dialog.setContentView(R.layout.dialog);
dialog.setTitle("Failsafe Setup");
ListView failListView = (ListView) dialog.findViewById(android.R.id.list);
Button dialogButtonReset = (Button) dialog.findViewById(R.id.dialogButtonReset);
Button dialogButtonSend = (Button) dialog.findViewById(R.id.dialogButtonSend);
dialogButtonReset.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
Toast.makeText(getActivity()," Failsafe Reset",Toast.LENGTH_SHORT).show();
);
dialogButtonSend.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
Toast.makeText(getActivity()," Failsafe Send",Toast.LENGTH_SHORT).show();
);
dialog.show();
return false;
// end of OnClickChild method
);
private void prepareListData()
listDataHeader = new ArrayList<String>();
listDataChild = new HashMap<String, List<String>>();
// Adding child data
listDataHeader.add("Connection");
listDataHeader.add("Mission Limits");
listDataHeader.add("Compass Calibration");
listDataHeader.add("Sensor Calibration");
listDataHeader.add("Failsafe");
// Adding child data
List<String> Connection = new ArrayList<String>();
Connection.add("USB");
Connection.add("Wi-Fi");
List<String> MissionLimits = new ArrayList<String>();
List<String> CompassCalibration = new ArrayList<String>();
List<String> SensorCalibration = new ArrayList<String>();
List<String> Failsafe = new ArrayList<String>();
Failsafe.add("Failsafe Setup");
listDataChild.put(listDataHeader.get(0), Connection); // Header, Child data
listDataChild.put(listDataHeader.get(1), MissionLimits);
listDataChild.put(listDataHeader.get(2), CompassCalibration);
listDataChild.put(listDataHeader.get(3), SensorCalibration);
listDataChild.put(listDataHeader.get(4), Failsafe);
【问题讨论】：
【参考方案1】：NPE 在这里：
failListView.setAdapter(adapter);
因为ListView 和android:id/list id 位于dialog.xml 布局中，即Dialog 布局，而不是fragment_settings.xml 中，即SettingsFragment 片段布局。
因此，使用 Dialog 的上下文或对象无法访问 onCreateView 中的 ListView
【讨论】：
那么我如何访问 dialog.xml 中的元素 @ρяσѕρєя K 我在 SettingsFragment.java 类中添加了一行代码，因此代码如下所示： View rootView = inflater.inflate(R.layout.fragment_settings, container, false); rootView2 = inflater.inflate(R.layout.dialog, 容器, false); failListView = (ListView) rootView2.findViewById(android.R.id.list);所以列表视图出现但它是空的，为什么项目没有出现？有什么帮助吗？ @jaradat: 从 onCreateView 返回 `rootView2` 它让我 NPE 指向 // 设置列表适配器 expListView.setAdapter(listAdapter); 我需要rootView和rootView2，我怎样才能得到这2个视图？？以上是关于在片段中使用列表视图的主要内容，如果未能解决你的问题，请参考以下文章