Develop Reference

Do I use ViewHolder correctly? Everithing is worked, but i still have doubts with the ListView optimization with holder recycler

I am just adapting my custom adapter code with ViewHolder so that i can optimize my list view with a recycler, but i am not sure if i do it right.
My view holder class:
public class ViewHolderTask {
int positionHolder;
TextView nameHolder;
TextView timeHolder;
TextView sessionHolder;
TextView dateHolder;
FloatingActionButton mFabTaskHolder;
public ViewHolderTask(View v, int position) {
this.positionHolder = position;
this.nameHolder = v.findViewById(R.id.taskNameText);
this.timeHolder = v.findViewById(R.id.timeTextView);
this.sessionHolder = v.findViewById(R.id.textViewSession);
this.dateHolder = v.findViewById(R.id.dateTextView);
this.mFabTaskHolder = v.findViewById(R.id.myFabTask);
}
My custom adapter class:
#NonNull
#Override
public View getView(int position, #Nullable View convertView, #NonNull ViewGroup parent) {
ViewHolderTask holder;
if(convertView == null){
LayoutInflater inflater = (LayoutInflater) context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE );
convertView = inflater.inflate(R.layout.task_row, parent, false);
holder = new ViewHolderTask(convertView, position);
convertView.setTag(holder);
}else{
holder = (ViewHolderTask) convertView.getTag();
}
Task task = taskArrayList.get(position);
//set the configurations
holder.getTimeHolder().setText(getTimeString(task.getTime()));
holder.getNameHolder().setText(task.getName());
holder.getDateHolder().setText(getDateString(task.getDate()));
holder.getSessionHolder().setText(getSessionString(task.getSession()));
//Set the FAB listener
addFabListener(holder.getmFabTaskHolder(), position);
//set the clicked background
if(TaskActivity.getIsClicked() && TaskActivity.getPositionClicked()-1 == position){
convertView.setBackgroundResource(R.color.backgroundSelectedItem);
}
return convertView;
}
Do I use it right?

Seems to be fine for me other than this portion of the code
//set the clicked background
if(TaskActivity.getIsClicked() && TaskActivity.getPositionClicked()-1 == position){
convertView.setBackgroundResource(R.color.backgroundSelectedItem);
}
You might need to reset the background resource back to default for the item which is not clicked. maybe you have to add "else" part to the "if"

How to implement getView when creating custom spinner

I want to have custom spinner that has image and a textView in drop down list so I created different layout and inflated it, and its working fine but for layout of spinner before pressing spinner I just want to have a text like "choose from list" but when I inflating with
android.R.layout.simple_spinner_item
for getView, I'm just getting a drop down arrow and not text
How to populate layout in getView, do i have to create new dataset? different from dropdown? here is my code: I'm implementing SpinnerAdapter for custom adapter
#Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
convertView = inflater.inflate(R.layout.spinner_item, parent, false);
ImageView iv = (ImageView) convertView.findViewById(R.id.iv);
TextView tv = (TextView) convertView.findViewById(R.id.tv1);
iv.setImageResource(R.drawable.flower);
tv.setText(itemList[position]);
return convertView;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
convertView = inflater.inflate(android.R.layout.simple_spinner_item,
parent, false);
return convertView;
}

Declare the ViewHolder Class inside your spinner adapter
private static class ViewHolder{
TextView tv_itemname;
}
And modify your getView() method like this:
public View getView(final int position, View convertView, ViewGroup parent) {
View vi = convertView;
SpinnerListAdapter.ViewHolder holder;
if(convertView==null){
vi = inflater.inflate(R.layout.spinner_item_row, null);
holder = new SpinnerListAdapter.ViewHolder();
holder.tv_itemname = (TextView) vi.findViewById(R.id.tv_itemname);
vi.setTag( holder );
}
else
{
holder = (SpinnerListAdapter.ViewHolder) vi.getTag();
}
if (position == 0)
{
holder.tv_itemname.setText("Choose one of the following category");
}else{
holder.tv_itemname.setText(itemList[position]);
}
return vi;
}

text1 is the identifier for TextView in android.R.layout.simple_spinner_item
#Override
public View getView(int position, View convertView, ViewGroup parent) {
convertView = inflater.inflate(android.R.layout.simple_spinner_item,
parent, false);
TextView text1 = (TextView) convertView.findViewById(android.R.id.text1);
text1.setText(itemList[position]);
return convertView;
}

Setting layout of first ListView Item

So I am attempting to set a different layout resource for my first ListItem element using this code:
int type;
#Override
public int getItemViewType(int position) {
if(position==0) {
type = R.layout.queue_item_next;
} else {
type = R.layout.queue_item;
}
return type;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = (View) inflater.inflate(getItemViewType(position), parent, false);
}
This code works however with some unexpected behavior. For some reason the last element of the ListView is also being set to have this alternate layout and I have no idea why.
What could cause this to happen?
Thanks.

Issue is coming due getItemViewType() is returning value greater than number of view types. You can use bellow code working perfectly fine for me.
#Override
public int getItemViewType(int position) {
if(position==0) {
return 0;
}
return 1;
}
#Override
public int getViewTypeCount() {
return 2;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
int type = getItemViewType(position);
if(type == 0)
convertView = (View) inflater.inflate(R.layout.first_layout, parent, false);
else
convertView = (View) inflater.inflate(R.layout.second_layout, parent, false);
}
}
Note : If only first view is different then best option is to use headerView using function listview.addHeaderView() function using this link

because you are using if(convertView == null) {}
that means if previous view is available in memory use that one else create a new one. So, sometimes on scroll fast/slow depends on resources available of phone it varies.
to solve this problem dont check if(convertView == null)
use like this
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = (View) inflater.inflate(getItemViewType(position), parent, false);
}

Gridview repeating images but not the text in android

In ImageView, my images are being shuffled but not the text. This is my getView() method:
public View getView(int position, View convertView, ViewGroup parent) {
View v;
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) mainActivity.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
v = inflater.inflate(R.layout.item_people, parent, false);
} else {
v = (View) convertView;
}
TextView textView = (TextView) v.findViewById(R.id.name);
ImageView imageView = (ImageView) v.findViewById(R.id.image);
if (list.get(position).getClass() == SearchData.Video.class) {
SearchData.Video video = (SearchData.Video) list.get(position);
textView.setText(video.getVideoName());
if (video.getCoverPicture().length > 0)
imageView.setBackground(mainActivity.Base64toImage(video.getCoverPicture()[0].getImg()));
} else if (list.get(position).getClass() == SearchData.Actor.class) {
SearchData.Actor actor = (SearchData.Actor) list.get(position);
textView.setText(actor.getFirstName());
if (actor.getPicture().length > 0)
imageView.setBackground(mainActivity.Base64toImage(actor.getPicture()[0].getImg()));
}
return v;
}
I am setting image and text of actors. When I scroll down then up the images have shuffled, but not text. Why?

Did you tried the same with ViewHolder
Normally when ever getView() method is called, the gridview/ listview will automatically notified as a change, So that is the reason for your image shuffling s / changing in your gridview.
So, try to implement your Gridview with ViewHolder pattern and avoid those shuffling s / re-orderings
here is the sample code for view holder pattern implementation.
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolderItem viewHolder;
// The convertView argument is essentially a "ScrapView" as described is Lucas post
// http://lucasr.org/2012/04/05/performance-tips-for-androids-listview/
// It will have a non-null value when ListView is asking you recycle the row layout.
// So, when convertView is not null, you should simply update its contents instead of inflating a new row layout.
if(convertView==null){
// inflate the layout
LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
convertView = inflater.inflate(layoutResourceId, parent, false);
// well set up the ViewHolder
viewHolder = new ViewHolderItem();
viewHolder.textViewItem = (TextView) convertView.findViewById(R.id.textViewItem);
// store the holder with the view.
convertView.setTag(viewHolder);
}else{
// we've just avoided calling findViewById() on resource everytime
// just use the viewHolder
viewHolder = (ViewHolderItem) convertView.getTag();
}
// object item based on the position
ObjectItem objectItem = data[position];
// assign values if the object is not null
if(objectItem != null) {
// get the TextView from the ViewHolder and then set the text (item name) and tag (item ID) values
viewHolder.textViewItem.setText(objectItem.itemName);
viewHolder.textViewItem.setTag(objectItem.itemId);
}
return convertView;
}
your ViewHodler should be like this
// ViewHolder.
// caches our TextView
static class ViewHolderItem {
TextView textViewItem;
}
This is not the exactly same to your question, but you can edit the above logic for your way.
Hope it Helps :)

Changing the size of cells in grid view?

I have a gridview in Android which is populated by a custom view which inherits from imagebuttons.
What I would like to do is modify the size of the imagebuttons inside the gridview as well as their padding between cells.
Here is my getView() code. I've tried using layouts but can't because I don't have access to the parent view.
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (image == null)
image = BitmapFactory.decodeResource(context.getResources(), R.drawable.dollar);
ExpenseIcon ic = new ExpenseIcon(context);
ic.setImageBitmap(image);
return ic;
}
How do I do that?

You can set the with with setColumnWidth(int) or set the column count by calling setNumColumns(int) depending on what you extactly trying. By the way you can also set that values by xml (android:columnWidth and android:numColumns).
For the spacing you can use android:horizontalSpacing or setHorizontalSpacing(int) and android:verticalSpacing or setVerticalSpacing(int).
For controling the highe you need to change your getView function:
public YourConstructor() {
// inflater should be a private member variable
inflater = (LayoutInflater)context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
// other code...
}
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null) {
// create new one and put it into convertView. e.g.:
convertView = new ExpenseIcon(context);
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(HEIGHT,WIDTH);
convertView.setLayoutParams(lp);
}
// set the image to the currient convertView. e.g.:
((ExpenseIcon)convertView).setImageBitmap(image);
return convertView;
}

Create an XML and inflate.I gave sample to use in getview...Set imagesize in the layout..
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.grid_item, null);
holder = new ViewHolder();
holder.image = (ImageView) convertView.findViewById(R.id.grid_item_image);
convertView.setTag(holder);
}else {
holder = (ViewHolder) convertView.getTag();
}
holder.image.setImageResource(list.get(position).getIconid());
return convertView;
}
static class ViewHolder {
ImageView image;
}