Custom view for groups ExpandableListView

Question

Tell me please .. made my markup for group headers in ExpandableListView . In the adapter wrote the following:

 public class ExpListAdapter extends SimpleCursorTreeAdapter { DBHeler dbHeler; private int layout; public ExpListAdapter(Context context, Cursor cursor, int groupLayout, String[] groupFrom, int[] groupTo, int childLayout, String[] childFrom, int[] childTo) { super(context, cursor, groupLayout, groupFrom, groupTo, childLayout, childFrom, childTo); this.layout = childLayout; } @Override public View newGroupView(Context context, Cursor cursor, boolean isExpanded, ViewGroup parent) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE); View view = inflater.inflate(layout, parent, false); ViewHolder viewHolder = new ViewHolder(view); view.setTag(viewHolder); return view; } @Override protected void bindGroupView(View view, Context context, Cursor cursor, boolean isExpanded) { super.bindGroupView(view, context, cursor, isExpanded); ViewHolder holder = (ViewHolder) view.getTag(); String category = cursor.getString(cursor.getColumnIndex(Contract.Entry.COLUMN_NAME)); holder.txtCategory.setText(category); } }

I get the error:

Process: test.myapp, PID: 6572 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText (java.lang.CharSequence) (ExpListAdapter.java:82)

Accepted Answer · 2017-02-16T06:28:38

The error is caused by the fact that you specify the wrong markup for a custom type of group:

 public class ExpListAdapter extends SimpleCursorTreeAdapter { DBHeler dbHeler; private int layoutChild; ptivate int layoutGroup; public ExpListAdapter(Context context, Cursor cursor, int groupLayout, String[] groupFrom, int[] groupTo, int childLayout, String[] childFrom, int[] childTo) { super(context, cursor, groupLayout, groupFrom, groupTo, childLayout, childFrom, childTo); dbHeler = new DBHeler(context); layoutChild = childLayout; layoutGroup = groupLayout; } @Override public View newGroupView(Context context, Cursor cursor, boolean isExpanded, ViewGroup parent) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE); View view = inflater.inflate(layoutGroup, parent, false); // разметка групп ViewHolder viewHolder = new ViewHolder(view); view.setTag(viewHolder); return view; } @Override public View newChildView(Context context, Cursor cursor, boolean isLastChild, ViewGroup parent) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE); View view = inflater.inflate(layoutChild, parent, false); // разметка вложенных ViewHolder viewHolder = new ViewHolder(view); view.setTag(viewHolder); return view; } }

To change the type of the group disclosure indicator, you need to draw two types of this indicator: closed and open, then write a selector, let's call its indicator.xml:

 <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_expanded="true" android:drawable="@drawable/group_indicator_expanded" /> <item android:drawable="@drawable/group_indicator" /> </selector>

file is placed in the folder res / drawable

Now in the markup of your ExpandableListView indicate this indicator:

 <ExpandableListView android:id="@+id/expandableListView1" android:layout_width="match_parent" android:layout_height="match_parent" android:groupIndicator="@drawable/indicator" > </ExpandableListView

>

I have this indicator stretched to the full height of the group, is it possible to make it not stretch, but be the same size as it was?
Specify the areas of stretching - the edges of your indicator, where there is no image, so that empty space is stretched.
@ Veronica to expand the first group expdListView.expandGroup(0);

Custom view for groups ExpandableListView

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