Question

我正在尝试通过在片段中扩展ExpandableListAdapter来实现ExpandableListview。与父节点一起显示片段时没有问题。一旦我单击父应用程序，就会停止并引发异常，并通过展开显示孩子

    E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.ekatechhp.pkmapplication, PID: 29388
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
    at com.example.ekatechhp.pkmapplication.holder.ExpandableListAdapter.getChildView(ExpandableListAdapter.java:50)
    at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:451)
    at android.widget.AbsListView.obtainView(AbsListView.java:2346)
    at android.widget.ListView.makeAndAddView(ListView.java:1876)
    at android.widget.ListView.fillDown(ListView.java:702)
    at android.widget.ListView.fillSpecific(ListView.java:1367)
    at android.widget.ListView.layoutChildren(ListView.java:1663)
    at android.widget.AbsListView.onLayout(AbsListView.java:2148)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1775)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:142)
    at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:41)
    at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1556)
    at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:888)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
    at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2678)
    at android.view.View.layout(View.java:16651)
    at android.view.ViewGroup.layout(ViewGroup.java:5440)
    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2183)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1943)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
    at android.view.Choreographer.doCallbacks(Choreographer.java:670)
    at android.view.Choreographer.doFrame(Choreographer.java:606)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
    at android.os.Handler.handleCallback(Handler.java:746)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.ja

我不明白为什么它会引发异常。在活动中，它起作用了，但出现了碎片问题

ExpandableListAdapter.java

    public class ExpandableListAdapter extends BaseExpandableListAdapter {

    private Context _context;
    private List<String> _listDataHeader; // header titles
    // child data in format of header title, child title
    private HashMap<String, List<String>> _listDataChild;

    public ExpandableListAdapter(Context context, List<String> listDataHeader,
                                 HashMap<String, List<String>> listDataChild) {
        this._context = context;
        this._listDataHeader = listDataHeader;
        this._listDataChild = listDataChild;
        }

    @Override
    public Object getChild(int groupPosition, int childPosititon) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .get(childPosititon);
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    @Override
    public View getChildView(int groupPosition, final int childPosition,
                             boolean isLastChild, View convertView, ViewGroup parent) {

        final String childText = (String) getChild(groupPosition, childPosition);

        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_item, null);
        }
        TextView txtListChild = (TextView) convertView.findViewById(R.id.lblListItem);
        txtListChild.setText(childText);
        return convertView;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .size();
    }

    @Override
    public Object getGroup(int groupPosition) {
        return this._listDataHeader.get(groupPosition);
    }

    @Override
    public int getGroupCount() {
        return this._listDataHeader.size();
    }

    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        String headerTitle = (String) getGroup(groupPosition);
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.my_know_list_group, null);
        }

        TextView lblListHeader = (TextView) convertView
                .findViewById(R.id.lblListHeader);
        lblListHeader.setTypeface(null, Typeface.BOLD);
        lblListHeader.setText(headerTitle);

        return convertView;
    }

    @Override
    public boolean hasStableIds() {
        return false;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
   }

Answer 1

以此替换您的代码

final String childText = (String) getChild(groupPosition, childPosition);

带有以下代码

final String childText =String.valueOf(getChild(groupPosition, childPosition));

因为您的方法getChild返回long，而textview需要String作为输入

在活动中未引发异常，更改为片段时适配器出现问题

1 个答案: