At the moment I have this code running. I am working in eclipse and at the moment am getting this error
The method getItem(int) is undefined for the type Expandable.MySimpleCursorTreeAdapter
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition,
int childPosition, long id) {
// use groupPosition and childPosition to locate the current item in the adapter
Intent intent = new Intent(Categories.this, com.random.max.Random.class);
Cursor cursor = (Cursor) mscta.getItem(childPosition);
intent.putExtra("EMPLOYEE_ID", cursor.getInt(cursor.getColumnIndex("_id")));
//Cursor cursor = (Cursor) adapter.getItem(position);
//intent.putExtra("EMPLOYEE_ID", cursor.getInt(cursor.getColumnIndex("_id")));
startActivity(intent);
return true;
}
You using a Cursor Adapter, Cursors can only be iterated over (in a sequence).
So there is no getItem(position) method because you cant pick a specific item.
Use a different Adapter for your underlying DataModel like a ArrayAdapter.
Ok here some code for a AdapterImplementation
first:
YourCustomAdapter extends ArrayAdapter<YourDataObject>
than you simple implement the inherited Methods, the important Methods are getView and getItem
in getView you define how the Data will be shown in your ListView.
Use ViewHolder to cache your Items for scrolling.
#Override
public View getView(int position, View convertView, ViewGroup parent) {
final ViewHolder holder;
View v = convertView;
if (v == null) {
v = inflater.inflate(layoutResource, null);
holder = new ViewHolder();
holder.firstLine = (TextView) v.findViewById(R.id.textview);
v.setTag(holder);
} else {
// Get the ViewHolder back to get fast access to the TextView
// and the ImageView.
holder = (ViewHolder) v.getTag();
}
holder.firstLine = "test";
return v;
}
basicly you fill your holder with your stuff and save it inside your View, the next time your dont have to fill in your Resources again.
the second method getItem(int position) is simple:
you have to specify how to get the item on position "position" on your DataStructure.
If you have an Array you could write:
#Override
public long getItem(int position) {
return myDataArray.get(position);
}
Related
listContent.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
for(int i=0;i<showLists.size();i++){
//
TextView v=(TextView)listContent.getChildAt(i).findViewById(R.id.txtDes);
v.setTextColor(Color.BLACK);
}
TextView v=(TextView)listContent.getChildAt(position).findViewById(R.id.txtDes);
v.setTextColor(Color.RED);
Toast.makeText(context,"POS "+showLists.get(position).getDes(),Toast.LENGTH_SHORT).show();
}
});
I have been the problem with get position item of listview. Android just has shown about 12 row on devide's creen, when I click another item on listview (my listview have 30 item ) which shown the error.
And this is error:
"Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference" .
Thanks for read.
listContent.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
for (int i = 0; i < showLists.size(); i++) {
TextView v = (TextView) view.findViewById(R.id.txtDes);
v.setTextColor(Color.BLACK);
}
TextView v = (TextView) view.findViewById(R.id.txtDes);
v.setTextColor(Color.RED);
Toast.makeText(context, "POS " + showLists.get(position).getDes(), Toast.LENGTH_SHORT).show();
}
});
Your question is indeed about Null Pointer Exception, but is harder to identify why this is happening. The problem can be found here:
for(int i=0;i<showLists.size();i++){ <-- this line actually causes the crash
//
the crash is in the next line, at the findViewById
TextView v=(TextView)listContent.getChildAt(i).findViewById(R.id.txtDes);
v.setTextColor(Color.BLACK);
}
Your for has the wrong upper limit because of a mechanism known as recycling, and because of this mechanism your list view will never have the same number of rows as the amount of data that needs to be displayed (read about recycling to understand this). Given this fact, we know for sure that the number of views found in list view (listContent.getChildCount()) will be smaller than showLists.size() and thus making the call listContent.getChildAt(i) to return a NULL value when the index equals listContent.getChildCount() creating the crash.
Now you might be tempted to change showLists.size() with listContent.getChildCount() and see that the app doesn't crash anymore, but if you click a row, then other rows are coloured also as you scroll the list (the recycling is again the problem). To really fix the problem you should save the index of the selected row and call notifyDatasetChanged, so when getView is called in adapter you simply check the current position to be displayed with the selected position. In case of equality you change the color of text to red, otherwise to black. Below, you will find some parts of an example:
int currentPosition = -1;
// Just a basic adapter. The getView method is the key here
final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1) {
#NonNull
#Override
public View getView(int position, #Nullable View convertView, #NonNull ViewGroup parent) {
View view = super.getView(position, convertView, parent);
if (position == currentPosition) {
((TextView) view).setTextColor(Color.RED);
} else {
((TextView) view).setTextColor(Color.BLACK);
}
return view;
}
};
// and here is the onItemClick
listView.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
currentPosition = position;
adapter.notifyDataSetChanged();
}
});
public View getView(int position, View convertView, ViewGroup parent)
{
LayoutInflater inflater= (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View viewRow=convertView;
if(viewRow==null){
viewRow=inflater.inflate(layout,parent,false);
viewHolder viewHolder=new viewHolder();
viewHolder.imgIcon = (ImageView) viewRow.findViewById(R.id.imgIcon);
viewHolder.txtDes = (TextView) viewRow.findViewById(R.id.txtDes);
viewRow.setTag(viewHolder);
}
viewHolder holder= (viewHolder) viewRow.getTag();
holder.imgIcon.setImageResource(listMoiNhat.get(position).getIcon());
holder.txtDes.setText(listMoiNhat.get(position).getDes());
if(position==currentpos){
holder.txtDes.setTextColor(Color.RED);
}
else {
holder.txtDes.setTextColor(Color.RED);
}
return viewRow;
}
//and here is create customListMoiNhat object
final customListMoiNhat customListMoiNhat=new customListMoiNhat(context,R.layout.moinhat_customlistview,showLists,currentpos);
customListMoiNhat.notifyDataSetChanged();
listContent.setAdapter(customListMoiNhat);
listContent.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
currentpos=position;
customListMoiNhat.notifyDataSetChanged();
}
});
I've created listview with dynamically items inside which contains two items: CheckBox and TextView. When user taps checkbox inside item it updates background color of textView. It works fine until this item is scrolled out of the visible for user space of list and I get error: java.lang.NullPointerException at com.viewactivities.AddNewPosition.changeTextColorWhenCheckBoxIsClicked(AddNewPosition.java:183).
I have also implemented interface with one method responsible for changing color. I have observed that method "changeTextColorWhenCheckBoxIsClicked" is fired also when item from listView is not visible anymore (Here it causes error). Can anyone help?
Code for class which contains listview and method to change color:
#Override
public void changeTextColorWhenCheckBoxIsClicked(int position) {
// TODO Auto-generated method stub
listView.getChildAt(position).findViewById(R.id.listViewItemText).setBackgroundColor(Color.BLUE);
}
And code from listView adapter:
#Override
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder viewHolder = null;
globalPosition = position;
if(convertView==null){
LayoutInflater inflater = ((AddNewPosition) mContext).getLayoutInflater();
convertView = inflater.inflate(layoutResourceId, parent, false);
viewHolder = new ViewHolder();
viewHolder.text = (TextView) convertView.findViewById(R.id.listViewItemText);
viewHolder.checkbox = (CheckBox) convertView.findViewById(R.id.listViewItemCheckBox);
viewHolder.checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
int getPosition = (Integer) buttonView.getTag(); // Here we get the position that we have set for the checkbox using setTag.
listOfObjects.get(getPosition).setCheckBoxEnabled(buttonView.isChecked()); // Set the value of checkbox to maintain its state. changeTextColorWhenCheckBoxIsClicked(getPosition);
}
});
convertView.setTag(viewHolder);
convertView.setTag(R.id.listViewItemText, viewHolder.text);
convertView.setTag(R.id.listViewItemCheckBox, viewHolder.checkbox);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
viewHolder.checkbox.setTag(position); // This line is important.
viewHolder.text.setText(listOfObjects.get(position).getTextFromListViewItemObject());
viewHolder.checkbox.setChecked(listOfObjects.get(position).getIsCheckedBoxEnabled());
//viewHolder.text.setBackgroundColor(Color.RED);
//ListViewItemObject tmpObject = listOfObjects.get(position);
//TextView listItemText = (TextView) convertView.findViewById(R.id.listViewItemText);
//CheckBox checkBox = (CheckBox) convertView.findViewById(R.id.listViewItemCheckBox);
//checkBox.setChecked(false);
//listItemText.setText(tmpObject.getTextFromListViewItemObject());
return convertView;
}
#Override
public void changeTextColorWhenCheckBoxIsClicked(int position) {
// TODO Auto-generated method stub
((AddNewPosition) mContext).changeTextColorWhenCheckBoxIsClicked(position);
}
ListView reuses its views so instead of using setTag() use a list to maintain the position.
viewHolder.checkbox.setTag(position); // This line is important.
Something like this -
Android Listview Scrolling challenge for row elements
I am developing an app using a ListView with a simple custom adapter, each row containing a CheckBox object. However, due to ListView's recycling feature (that I don't plan on turning off), when any of the boxes are checked, others below or above in the ListView are also checked.
The following is my getView() in the adapter, along with the custom ViewHolder class:
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
LayoutInflater mInflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = mInflater.inflate(R.layout.populate_friends_row, null);
holder = new ViewHolder();
holder.nameCheckBox = (CheckBox) convertView.findViewById(R.id.isFriend);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.nameCheckBox.setText(data.get(position).contactLabel);
holder.nameCheckBox.setChecked(checked.get(position));
holder.nameCheckBox.setTag(String.valueOf(position)); // to properly track the actual position
holder.nameCheckBox.setOnCheckedChangeListener(new OnCheckedChangeListener(){
#Override
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
int pos = Integer.parseInt(buttonView.getTag().toString());
checked.set(pos, isChecked);
}
});
return convertView;
}
public static class ViewHolder {
public CheckBox nameCheckBox;
}
I am already holding the checked boxes in the ArrayList of booleans: checked.
Any help would be appreciated, thank you.
When you're calling holder.nameCheckBox.setChecked(checked.get(position)); to configure the view to be displayed for this view, the listener is called while the tag still has the position of the previous checkbox.
Try removing the listener (setting it to null) before calling setChecked
I got the following App with Costume adapter showing 2 images and 1 textview for each listview.
I can push/click/press each ListView just fine but i want to being able to recognize the X press aswell and i seem to not being able to get the view name or resource name.
My mainclass with the setOnItemclickListener looks like this
serverListView.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) {
//recieve and check if X image is pressed
}
});
This is the getView method in my Adapter. I tried to recognize the different image clicks in here without any different results.
#Override
public View getView(final int position,final View convertView,final ViewGroup parent) {
View row = convertView;
ServerHolder holder = null;
if(row == null){
LayoutInflater inflater = ((Activity)context).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent, false);
holder = new ServerHolder();
holder.imgIcon = (ImageView)row.findViewById(R.id.thumbImage);
holder.txtTitle = (TextView)row.findViewById(R.id.name);
holder.removeIcon = (ImageView)row.findViewById(R.id.removeServer);
row.setTag(holder);
}
else{
holder = (ServerHolder)row.getTag();
}
RowServer rs = servers.get(position);
holder.imgIcon.setImageResource(rs.getIcon());
holder.txtTitle.setText(rs.getName());
return row;
}
You probably have to add listeners to the subitems in getView(...). Try setOnClickListener(...) for the views you want to have events attached.
I have a GridView with custom View in it, which is a Button and a TextView. I defined the setOnItemClickListener but it looks like it never invoked, please see peaces of code below.
gridview = (GridView) findViewById(R.id.main_gridview);
gridview.setAdapter(new GridAdapter(this));
gridview.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(getApplicationContext(), "gadsfadsf",
Toast.LENGTH_SHORT).show();
Log.d("Main", "onItemClick");
}
});
The marked answer is kind of a hack. Instead of setting an onclicklistener to the button just ensure, that the ButtonView and the TextView has the following property:
android:clickable="false"
I had the same issue. While I've not yet figured out why it never gets invoked, I can propose a workaround.
Instead of setting the onClickListener on your GridView, set it on the Button itself inside your GridAdapter, inside your getView() method.
That worked for me!
It could be that some items in your GridView are stealing focus. Try adding these attributes to any elements you have inside the grid:
android:focusable="false"
android:focusableInTouchMode="false"
Instead of setting the onClickListener on your GridView,
set it on the Button itself inside your GridAdapter, inside your getView() method.
That worked for me!
I had the same problem, the event grid.itemClickListener was never launched.
In my case I had two listeners: grid.itemClickListener and another clickListener attached to a Button within the item's layout.
After fiddling with the layout for a while, I realized that if there was a widget, within the item's layout, with focusable=true, then itemClickListener was never launched. The clickListener attached to the Button worked well though.
Maybe that was your case. Anyway, I think this information might be useful to other users running into the same problem.
Thanx to CodingUser
what we were doing is directly accessing the Layout inside the GridView, so the onItemClickListener finds it confusing to access the item.
So the solution is to apply the onClickListener inside the Adapter (i.e. normally ArrayAdapter)
so what i m trying to say is:
public View getView(int position, View convertView, ViewGroup parent) {
//Here row is a view and we can set OnClickListener on this
final View row;
ViewHolder holder = null;
if (convertView == null) {
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
//Here we inflate the layout to view (linear in my case)
row = inflater.inflate(layoutResourceId, parent, false);
holder = new ViewHolder();
holder.imageTitle = (TextView) row.findViewById(R.id.text);
holder.image = (ImageView) row.findViewById(R.id.image);
row.setTag(holder);
} else {
row = convertView;
holder = (ViewHolder) row.getTag();
}
ImageItem item = data.get(position);
holder.imageTitle.setText(item.getTitle());
holder.image.setImageBitmap(item.getImage());
//Now get the id or whatever needed
row.setId(position);
// Now set the onClickListener
row.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(context, "Clicked" + row.getId() + "!!",
Toast.LENGTH_SHORT).show();
}
});
return row;
}
You can set OnClick for view in Adapter of GridView .It work for me .
public View getView(final int position, View convertView, ViewGroup parent) {
ObjMenuVideo objListVideo = mListMenuVideo.get(position);
final ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
inflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.item_video_of_kind, null);
holder.tv_number_views = (TextView) convertView
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.tv_number_views.setText(String.valueOf(objListVideo.getViews()));
convertView.setId(position);
convertView.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent menuVideoIntent = new Intent(mContext,
ActivityDetailVideo.class);
mContext.startActivity(menuVideoIntent);
}
});
return convertView;
}