Can someone explain this issue to me ?
I have a listview that holds more rows than the screen can show, so scrolling.
If I click on one item, I replace an icon that is part of each row. That all works.
The issue I have is that when I click on lets say the first item, I change the icon for that first row. When I now scroll down I see that the first row outside the visible viewport also changed the icon.
Why is that happening and how can I avoid this issue ?
Thanks in advance,
Mozzak
Just to make sure, you are using a class that implements ListAdapter or extends some other sort of adapter right?
When using an adapter, you will have to keep in mind that the views in the ListView are recycled to save memory. Because of this, you will need to store the state in a separate variable.
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null)
{
LayoutInflater inflator = (LayoutInflater)parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflator.inflate(R.layout.listitem, null);
}
// Retreive my image that may or may not change
ImageView myIcon = (ImageView) convertView.findViewById(R.id.iconView);
// Checking my stored boolean for this position to see if I need to use icon2 or icon
if (myItem[position].needsIconChanged)
{
// I have set my boolean, so use icon2
myIcon.setImageResource(R.drawable.icon2);
}
else
{
// I have not set my boolean, or set it to false so set it to icon
myIcon.setImageResource(R.drawable.icon);
}
return convertView;
}
You will also have to remember to set that boolean in your onItemCLick
public void onItemClick(AdapterView<?> myAdapter, View myView, int position, long arg3) {
// Retreive your item and set a boolean or icon state (depending on what you do)
myAdapter.getItemAtPosition(position).needsIconChanged = true;
}
Related
I have an app that displays a list of articles, which when clicked on changes its background color to green. The ListView is expanded by ViewPager. The color change occurs so that the user knows which articles has been read.
It is also remembered, so that the next time the user loads up the same list, items that have been clicked on remains green. The code below is what I used to make this work. The problem that I am now having is that, when pressing down long enough for the context menu to appear, my articles on ListView no longer changes color upon selection.
Before I instigated the green background change for each item that is clicked on, selecting items in the ListView (context mode) used to get grayed out. The context menu and functionality still works, but it no longer shows which items have been selected. Please can someone advise?
public void onListItemClick(ListView l, View v, int postion, long id) {
Article a = ((toReadListAdapter) getListAdapter()).getItem(postion);
// when item has been clicked on, variable is set to true.
a.setRead(true);
saveToReadList(toReadList);
.....
Custom Adapter:
// Defining custom adapter
private class toReadListAdapter extends ArrayAdapter<Article> {
public toReadListAdapter(ArrayList<Article> listToRead) {
super(getActivity(), 0, listToRead);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = getActivity().getLayoutInflater().inflate(R.layout.new_articlelistfragment, null);
}
Article en = getItem(position);
.....
/*if the article has been clicked on, then read attribute value is true and
background is green*/
if(en.isRead()){
convertView.setBackgroundColor(Color.parseColor("#C8E6C9"));
}else{
convertView.setBackgroundColor((Color.parseColor("#ffffff")));
}
/* convertView.setBackgroundColor(Color.parseColor("#66BB6A"));*/
return convertView;
In the onClickListener() of listView item set
CheckedTextView item = (CheckedTextView)view;
if(item.isChecked()){
convertView.setBackgroundColor(Color.parseColor("#C8E6C9"));
}
I have the following situation.
I have a ListView, each item of the ListView is comprised of different widgets (TextViews, ImageViews, etc...) inflated form a Layout in the getView() method of the custom adapter.
Now, I would like to achieve the following:
when a certain event is triggered I want to change the background of a View which is inside the item.
Please how do I do it?
This is the the Item Layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/cardlayout"
android:layout_width="320dp"
android:layout_height="130dp"
android:background="#android:color/transparent"
android:orientation="vertical"
android:paddingBottom="5dp"
android:paddingRight="5dp"
android:paddingTop="5dp" >
<FrameLayout
android:layout_width="320dp"
android:layout_height="117dp" >
<View
android:id="#+id/card"
android:layout_width="320dp"
android:layout_height="117dp"
android:background="#drawable/card_selector" />
</FrameLayout>
</LinearLayout>
I need to change the background of card
I have tried doing this:
View v=lv.getAdapter().getView(index, null, lv);
View card =(View)v.findViewById(R.id.card);
card.setBackgroundResource(R.drawable.pressed_background_card);
But no success :-((
When your event is triggered you should just call a notifyDataSetChanged on your adapter so that it will call again getView for all your visible elements.
Your getView method should take into account that some elements may have different background colors (and not forget to set it to normal color if the element doesn't need the changed background, else with recycling you would have many elements with changed background when you scroll)
edit :
I would try something like this :
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null)
{
convertView = LayoutInflater.from(getContext()).inflate(R.layout.card, parent, false);
}
//This part should also be optimised with a ViewHolder
//because findViewById is a costly operation, but that's not the point of this example
CardView cardView =(CardView)convertView .findViewById(R.id.card);
//I suppose your card should be determined by your adapter, not a new one each time
Card card = getItem(position);
//here you should check sthg like the position presence in a map or a special state of your card object
if(mapCardWithSpecialBackground.contains(position))
{
card.setBackgroundResource(specialBackground);
}
else
{
card.setBackgroundResource(normalBackground);
}
cardView.setCard(card);
return convertView;
}
And on the special event i would add the position of the item into the map and call notifyDataSetChanged.
Use the onitemclicklistener which has method onclicksomething..that takes four or five parameters. (View parent, View view, int position, int id). Use the view parameter to customize your background.
Update
Here's some of my code, If you don't understand I recommend to read about recycling and ViewHolder pattern.
#Override
public View getView(int position, View convertView, ViewGroup parent) {
{
ViewHolder viewHolder;
// If convertView isn't a recycled view, create a new.
if(convertView == null){
LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.row_gallery_frame, parent, false);
viewHolder = new ViewHolder();
// Here you must be able to find your Widget inside convertView and set a listener to it I guess?
viewHolder.nameHolder = (TextView) convertView.findViewById(R.id.nameTv);
// Set a reference to newly inflated view
convertView.setTag(viewHolder);
}
// If it is, then get the ViewHolder by tag
else{
viewHolder = (ViewHolder)convertView.getTag();
}
// Set the data
GalleryFrame galleryFrame = galleryFrameArrayList.get(position);
viewHolder.nameHolder.setText(galleryFrame.getName());
return convertView;
}
}
// Viewholder pattern which holds all widgets used
public static class ViewHolder{
public TextView nameHolder;
}
I assume you have a model object that you use to "draw" the list item , and for example the background color is determined based on a boolean or something.
All you need to do, is change the value on which you base your decision which background color should that TextView have.
Your getView() method should have code like that
if (myModelObj.isBrown()) {
myTextView.setBackgroundResource(R.drawable.brown_bg);
else
myTextView.setBackgroundResource(R.drawable.not_brown_bg);
All you should do when ur event is triggered, is set the value of the brown boolean in your model
and call notifyDataSetChanged() on your adapter
EDIT
If for some reason you don't wanna call nofitfyDataSetChanged(), althought it won't move the scroll position of your list and with the right recyclying it won't cause bad performance
You can find the View object that represent the list item you want to edit-if it's visisble-, and simply change the background in it, without refreshing the list at all.
int wantedPosition = 10; // Whatever position you're looking for
int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount();
int wantedChild = wantedPosition - firstPosition
if (wantedChild < 0 || wantedChild >= listView.getChildCount()) {
// Wanted item isn't displayed
return;
}
View wantedView = listView.getChildAt(wantedChild);
then use wantedView to edit your background
This answer can be found here
try this one:
View v=lv.getAdapter().getView(index, null, lv);
View card =(View)v.findViewById(R.id.card);
card.setBackgroundResource(R.drawable.pressed_background_card);
card.invalidate();
v.invalidate();
those function force your views to redraw itself and they will render again.
look at invalidate()
What I normally do is this:
public static class EventDetailsRenderer {
private TextView title;
private TextView description;
private Event item;
public EventDetailsRenderer(View view) {
extractFromView(view);
}
private final void extractFromView(View view) {
title = (TextView) view.findViewById(R.id.EventTitle);
description = (TextView) view.findViewById(R.id.Description);
}
public final void render() {
render(item);
}
public final void render(Event item) {
this.item= item;
title.setText(item.getTitle());
description.setText(item.getDescription());
}
}
private class EventsAdapter
extends ArrayAdapter<Event> {
public EventsAdapter(Context context) {
super(context, R.layout.list_node__event_details, 0);
}
public void addAllItems(Event... services) {
for (int i = 0; i < services.length; i++) {
add(services[i]);
}
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Event event = getItem(position);
EventDetailsRenderer eventRenderer;
if (convertView != null && convertView.getTag() != null) {
eventRenderer = (EventDetailsRenderer) convertView.getTag();
} else {
convertView = getActivity().getLayoutInflater().inflate(R.layout.list_node__event_details, null);
eventRenderer = new EventDetailsRenderer(convertView);
convertView.setTag(eventRenderer);
}
eventRenderer.render(event);
return convertView;
}
}
NOTE: that this example might not compile I pasted it from some code I have and deleted some lines to show an example but the logic it the same.
And then when you want to render it, just get the children from the list, iterate over them, check if the renderer contains the card you want to flip and call its render method... then you render a specific item in the list without effecting the rest of the items.
Let me know if this works...
Adam.
User EasyListViewAdapters library https://github.com/birajpatel/EasyListViewAdapters
Features
Easier than implementing your own Adapter (ie handling
BaseAdaper#getView).Very Easier to provide multi-row support.
Library takes care of recycling all views, that ensures performance
& helps your list view scroll smoothly.
Cleaner code. By keeping different RowViewSetter classes for
different row-types makes your code easy to manage & easy to reuse.
No data browsing, Library takes care of browsing data through
data-structure when View is being drawn or event occurs so that
Users does not have to look for their data to take actions.
Just by passing correct row-types library will Auto-map your
data-types to row-types to render views. Row views can be created by
using XML or Java (doesn't restrict to XML-Only Approach).
Load More callbacks can be registered to implement paginatation
support to your list.
Handling children viewclicks, you can also register for
Children(present inside your rows) view click events.
All these Views are registered with single OnClickListner so that
this mechanism is very memory efficient when click event occurs
users you gets clickedChildView, rowData,int eventId as callback
params.
I have a ListView with lots of icons which may be clicked to change the state of their respective row items. I realise that I can create onClick handlers for all of them but I would like to a generic means of identifying which icon (View) has been clicked. (e.g. determine View at touch coords x,y?
Any idea how I can do that?
I am getting row clicks with the below handler:
lvClickListener = new AdapterView.OnItemClickListener()
{
#Override
public void onItemClick( AdapterView<?> arg0, View arg1, int position, long arg3 )
...
On each row I have 5 ImageViews.
I assume all rows are being inflated with the same layout and you are using the holder pattern (http://developer.android.com/training/improving-layouts/smooth-scrolling.html).
This way, you can have a single OnClickListener to "listen" for any of your ImageView (or whatever they are). You only need to set the listener in the momento you actually inflate the view (not when you reuse it), and then set for all ImageView in the same row the row position as the Tag, so, then in the onClick method, you can chech to which row they belong to (by the tag) and which ImageView is it (by the id)
class MyAdapter extends BaseAdapter implements OnClickListener
[...]
#Override
public View getView (int position, View convertView, ViewGroup parent)
{
MyHolder holder = null;
if(convertView != null)
{
holder = new MyHolder();
convertView = inflater.inflate(...)
holder.imageView1 = (ImageView)convertView.findViewById(R.id.[...] )
holder.imageView1.setOnClickListener(this);
holder.imageView2 = (ImageView)convertView.findViewById(R.id.[...] )
holder.imageView2.setOnClickListener(this);
[...]
convertView.setTag(holder);
}
else
{
holder = (HyHolder)convertView.getTag();
[...]
}
holder.imageView1.setTag(position);
holder.imageView2.setTag(position);
[...]
return convertView;
}
#Override
public void onClick(View v)
{
int id = v.getId();
Integer position = (Integer)v.getTag();
[...]
}
Of course you can then optimize this, put the views in an array or whatever or put the OnClickListener outside the Adapter (in the activity, or an instance variable), but this is the basic idea.
As a note, you should check what happens with the onItemClickListener, I'm not pretty sure, but it may cause problems intercepting touches (or it may no, I don't know), but if you're not going to use the whole row click, then you can remove it
You can do this in multiple ways, You can tag each ImageView to your AsyncTask(or whatever) you use. Or, refer https://github.com/square/picasso
After looking for some answers here, I find myself in a disturbing situation where my Listview is really getting on my nerve.
Here are the questions I looked for :
Maintain ListView Item State
How to save state of CheckBox while scrolling in ListView?
I'm using a custom adapter with a custom row as below.
My Listview is simple as it is displaying a custom row made of three elements :
1) an ImageView displaying contact picture cropped in a circle ;
2) a TextViewdisplaying the contact full name as plain text ;
3) and finally an ImageView that holds the purpouse of a CheckBox.
Please focus on the last element. The ImageView CheckBox-like will have its src changed upon click.
When the user click, the ImageView will switch between a check sign and an unchecked sign according to it's previous status. Possible status are : {checked | unchecked}
So far so good.
But as soon as I scroll the ListView, any aforementioned change will disappear as Android recycle unused view.
Here comes the so-called ViewHolder pattern. Unfortunately, this pattern is failling me on two issues :
First, when scrolling, my organized-in-an-alphabetical-order listview gets disorganized.
e.g. somehow, whitout any reason, the first displayed contact name gets displayed again later on the ListView as I scrolled. That can happen with any row ! So it would seem unused view are being wrongly re-used.
Second, and in accordance to the first issue, the checked status do seem to stay, but not always and if it does stay, it may very well stay on the wrong row ... and that can happen randomly, of course. Therefore ViewHoder is not a viable solution.
Before discouvering the ViewHolder pattern, I have been using a HashMap to store the item position upon click as followed :
ContactsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public final void onItemClick(final AdapterView<?> adapterView, final View view,
final int position, final long id) {
final ImageView check = (ImageView) view.findViewById(R.id.checkImage);
final TextView name = (TextView) view.findViewById(R.id.contactName);
final Boolean isChecked = Boolean.valueOf(checkedContactsList.isChecked(position));
if (isChecked != null && isChecked.booleanValue() == true) {
check.setImageDrawable(getActivity().getResources().getDrawable(R.drawable.unchecked_sign));
checkedContactsList.(position);
} else {
check.setImageDrawable(getActivity().getResources().getDrawable(R.drawable.checked_sign));
checkedContactsList.add(position, true);
}
}
});
I tried adding a different value instead of position.
I tried with ContactsListView.getPositionForView(view)
And I also tried with the View's ID, but still it doesn't work.
I wish I could use ContactsListView.getSelectedItemPosition() but it returns -1 as there is no selection event because I'm handling a touch/click event.
And this is how my Custom Adapter looks like :
public final View getView(final int position,
final View convertView, final ViewGroup parent) {
final LayoutInflater inflater = (LayoutInflater) this.context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final View contactRowView = inflater.inflate(R.layout.contact_row, parent, false);
final ImageView contactPic = (ImageView) contactRowView.findViewById(R.id.contactPic);
final TextView contactName = (TextView) contactRowView.findViewById(R.id.contactName);
final ImageView checkImage = (ImageView) contactRowView.findViewById(R.id.checkImage);
// the list is the same as above and therefore contains the exact same entries
if (this.checkedContactsList.isChecked(position))
checkImage.setImageDrawable(this.context.getResources().getDrawable(R.drawable.checked_sign));
contactPic.setImageBitmap(cropePictureInCircle(this.contacts.get(position).getPicture()));
contactName.setText(this.contacts.get(position).getName());
return contactRowView;
}
Is there a good way to keep the checked row checked and the unchecked row unchecked in the given alphabetical order ?
Thanks !
For the list position change I know the solution but for the second problem I am still searching for a solution, anyway first make a viewHolder class;
public class ViewHolder{
//put all of your textviews and image views and
//all views here like this
TextView contactName;
ImageView checkImage;
ImageView contactImage;
}
Then edit your adapter:
#Override
public View getView(int position, View convertView, ViewGroup parent)
{
final View contactRowView = convertView;
ViewHolder holder;
if (contactRowView == null) {
final LayoutInflater inflater = (LayoutInflater)
this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE
);
contactRowView =
inflater.inflate(R.layout.contact_row, parent,
false);
holder = new ViewHolder():
holder.contactPic = (ImageView)
contactRowView.findViewById(R.id.contactPic);
holder.contactName = (TextView)
contactRowView.findViewById(R.id.contactName);
holder.checkImage = (ImageView)
contactRowView.findViewById(R.id.checkImage);
contactRowView.setTag(holder);
} else {
holder = contactRowView.getTag();
// the list is the same as above and therefore contains the exact same entries
if (this.checkedContactsList.isChecked(position))
holder.checkImage.setImageDrawable(this.context.get.
Resources().getDrawable(R.drawable.checked_sign));
holder.contactPic.setImageBitmap(cropePictureInCircle(this.contacts.get(position).getPicture()));
holder.contactName.setText(this.contacts.get(position).getName());
return contactRowView;
}
}
Hope this helps and sorry because writing code from my phone is totally awkward.
I have got a Gridview in my app. I then added a OnItemLongClickListener to that GridView. Check out this code:
myGridView.setOnItemLongClickListener(new OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view,
int position, long id) {
view.setBackgroundResource(R.drawable.image_border);
return true;
}
});
Now, all I want to do is set a border to an image in my gridview. The problem with my code is that it sets the border to an image but when I start scrolling up and down, suddenly an other image has got the border although it was never clicked.
How come that the border gets set to other images as well. Any idea how I can fix this?
Your Adapter class does this internally to reduce memory consumption and to efficiently use device resources.
In your Adapter class you should do
public View getView (int position, View convertView, ViewGroup parent){
// convertView is reused from previously scrolled out view to reduce memory consumption
if( convertView == null ){
//We must create a View:
convertView = inflater.inflate(R.layout.my_list_item, parent, false);
}
// Set border to the image if it is selected otherwise set it to default
// keep in mind when you add any condition here, else should also be addressed
return convertView;
}