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
Related
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've a question about ListView and listeners.
Suppose i have a listview in my app. Each item of it contains a checkbox.
And i've the following code:
public View getView(final int position, View convertView, ViewGroup parent) {
CheckBox checkbox = (CheckBox)v.findViewById(R.id.checkbox);
checkbox.setOnCheckedChangeListener(new OnCheckedChangeListener(){
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// some code
}
});
}
As you can see I set setOnCheckedChangeListener every time when getView method is called.
So is it right way to set listener? Or should I set it once? Is it bad in terms of performance? Or it doesn't matter? And if I set the listener multiple times whether it will overwrite previous listener or will i have multiple listeners for this event?
Each listener that you set will overwrite the previous one (if any). Setting a listener, or anything else, will consume a super small amount of time, however here you're also creating a new anonymous class which will take longer.
For the maximum performance, I would make a few adjustments:
Use convertViews to cache the views
Use ViewHolder pattern to avoid multiple findViewById calls
Use a single listener for all checkboxes and set it only on the cached views (if convertView == null)
Save the position of the item that the CheckBox is located in as the CheckBox's tag
Here's an example:
private static class ViewHolder {
CheckBox checkBox;
}
private CompoundButton.OnCheckedChangeListener mCheckListener = new CompoundButton
.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
Log.e("TAG", "CheckBox position: " + buttonView.getTag());
}
};
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
/* Inflate the layout here */
holder = new ViewHolder();
holder.checkBox = (CheckBox) convertView.findViewById(R.id.checkbox);
/* Find other views in you layout here */
holder.checkBox.setOnCheckedChangeListener(mCheckListener);
// Set the holder as tag, so you can fetch it later for re-use
convertView.setTag(holder);
} else {
// Fetch the holder
holder = (ViewHolder) convertView.getTag();
}
// Set the checkbox position
holder.checkBox.setTag(position);
return convertView;
}
If you're not familiar with using convertViews and the ViewHolder pattern you should watch The World of ListView that explains it all.
Is it bad in terms of performance? Or it doesn't matter?
It does not matter. The setter just assign the object.
And if I set the listener multiple times whether it will overwrite
previous listener or will i have multiple listeners for this event?
you will have just one for each instance of the checkbox upon you called setOnCheckedChangeListener. The ListView is particular case due of its recycling mechanism
I know that many similar questions have been posted on stackoverflow, so please don't think I haven't searched high and low. I think my problems simply comes from now completely understanding listViews and the lifecycles of list items. I have a list view that can contain two types of messages, outbound or inbound. Originally, my listView would use a different background color depending on the type of message (outbound vs inbound), and it worked flawlessly. Now my application doesn't require a different background for list items, but it actually requires different layouts for different list items.
This is a clip of my Adapter.
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
SoapBoxMessage thisMessage = messages.get(position);
if (v == null) {
LayoutInflater inflater = (LayoutInflater) getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (thisMessage.isOutbound()) {
v = inflater.inflate(R.layout.outbound_row, null);
} else {
v = inflater.inflate(R.layout.inbound_row, null);
}
}
Adapters can support different ViewItemTypes that will solve your recycling problems.
static public enum LAYOUT_TYPE {
INBOUND,
OUTBOUND
}
#Override
public int getViewTypeCount () {
return LAYOUT_TYPE.values().length;
}
#Override
public int getItemViewType (int position) {
if ( messages.get(position).isOutbound())
return LAYOUT_TYPE.OUTBOUND.ordinal();
else
return LAYOUT_TYPE.INBOUND.ordinal();
}
#Override
public View getView (int position, View convertView, ViewGroup parent) {
LAYOUT_TYPE itemType = LAYOUT_TYPE.values()[getItemViewType(position)];
... (code until inflater )
switch (itemType){
case INBOUND:
convertview = /inflate & configure inbound layout
break;
case OUTBOUND:
convertview = /inflate & configure outbound layout
break;
}
you don't need to worry about recycling views because the listview will respect the ViewItemTypes for each position and it will only provide a convertview of the correct viewtype for that position
The problem is that listview is recycling the view so when you check if the view is null it wont pass that because the view is not null when it is recycled
you would need to inflate the view each time getView is called, basically removing if(v == null)
Try to use a ViewHolder like this:
ViewHolder holder;
public View getView(int position, View convertView, ViewGroup parent) {
convertView = null;
SoapBoxMessage thisMessage = messages.get(position);
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (thisMessage.isOutbound()) {
convertView = inflater.inflate(R.layout.outbound, null, false);
//specific to your outbound layout
holder = new ViewHolder();
holder.text= (TextView)convertView.findViewById(R.id.textview);
holder.group = (RadioGroup)convertView.findViewById(R.id.toggleGroup);
holder.toggle = (ToggleButton)convertView.findViewById(R.id.toggleButton);
} else {
convertView = inflater.inflate(R.layout.inbound, null, false);
//specific to your inbound layout
holder = new ViewHolder();
holder.text= (TextView)convertView.findViewById(R.id.textview);
holder.group = (RadioGroup)convertView.findViewById(R.id.toggleGroup);
holder.toggle = (ToggleButton)convertView.findViewById(R.id.toggleButton);
}
convertView.setTag(holder);
}
else{
holder = (ViewHolder) convertView.getTag();
}
//Here you can set the text or other code you want to implement
holder.text.setText("Whatever!");
return convertView;
}
static class ViewHolder {
//TODO put components you use like:
TextView text;
RadioGroup group;
ToggleButton toggle;
}
It's because of the recycling that is happening. You would need something along these lines:
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
SoapBoxMessage thisMessage = messages.get(position);
if (convertView == null) {
LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
convertView = mInflater.inflate(R.layout.listview_feedlog_item, null);
holder = new ViewHolder();
holder.txtTime = (TextView) convertView.findViewById(R.id.textTime);
holder.txtDate = (TextView) convertView.findViewById(R.id.textDate);
convertView.setTag(holder);
} else
holder = (ViewHolder) convertView.getTag();
// I don't know how your SoapBoxMessage is made up so here are two sample methods
holder.txtTime.setText(thisMessage.getTime());
holder.txtDate.setText(thisMessage.getDate());
return convertView;
}
/* private view holder class */
private class ViewHolder {
TextView txtTime;
TextView txtDate;
}
Also, remember to always reset or initiate a value in the getView method. Since a View can be recycled it might carry with it properties of its former life.
Whether this is a good practice or not, Removing if (v == null) will solve the problem.
Anyway, you will have to re-inflate the view.
I have developed an app in which I display data in Gridview. All data comes from local storage. I am able to display each data correctly and there are no issues with it. But when I have scroll the Gridview and goto the bottom and getback to Top,it changes position. And sometimes when I scroll down and getback to Top, a blank screen appears on screen;no data found at all!
So I thought that there is issue with getView(). I am unable to figure out the problem
Code of getView():
#Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder viewholder;
// LayoutInflater inflator = activit.getLayoutInflater();
if(convertView == null) {
// recycled view is null so create it.
viewholder = new ViewHolder();
convertView = inflator.inflate(R.layout.gridviewrow, null);
viewholder.imgvGridicon = (ImageView) convertView.findViewById(R.id.imgvGridicon);
viewholder.txtGridItemlabel = (TextView) convertView.findViewById(R.id.txtGridItemlabel);
convertView.setTag(viewholder);
} else {
viewholder = (ViewHolder) convertView.getTag();
}
if ((lstpinfo.get(position).appname.toString()) != null) {
viewholder.imgvGridicon.setImageDrawable((lstpinfo.get(position).icon));
viewholder.txtGridItemlabel.setText(lstpinfo.get(position).appname.toString());
}
return convertView;
}
Update::
Intitalize of inflater::
private LayoutInflater inflator;
private ArrayList<PInfo> lstpinfo = new ArrayList<PInfo>();
public GridViewAdapter(Context cntx, ArrayList<PInfo> lstpinfo) {
activit = cntx;
inflator = LayoutInflater.from(cntx);
this.lstpinfo = lstpinfo;
}
You have to set your view height with fixed value. There's a scrolling bug in android gridview with different heights. Please see this for reference.
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;
}