Related
I understand how a ViewHolder's onBindViewHolder works, however I'm unclear about how notifyItemRangeChanged(0, this.data.size()); works in this example and what it does exactly.
The data that is supplied to this adapter is in Json format.
The adapter is below:
public class AdapterQuestion extends RecyclerView.Adapter<AdapterQuestion.ViewQuestion>{
private LayoutInflater mLayoutInflater;
//this is an arrayList of questionData objects
private ArrayList<QuestionData> data =new ArrayList<>();
//Created the layoutInflator
public AdapterQuestion(Context context){
//get from context
mLayoutInflater=LayoutInflater.from(context);
}
public void setBloglist(ArrayList<QuestionData> data){
this.data =data;
notifyItemRangeChanged(0, this.data.size());
}
#Override
public ViewQuestion onCreateViewHolder(ViewGroup parent, int viewType) {
//inflates the customQuestion view or converts it to java code
View view= mLayoutInflater.inflate(R.layout.customquestion, null);
//We now want to convert the View into a ViewQuestion, view Question takes
//a view so we pass the view into view question and then return it.
ViewQuestion holder=new ViewQuestion(view);
return holder;
}
//ViewGroup parent and ViewType are not being assigned.
#Override
public void onBindViewHolder(ViewQuestion holder, int position) {
//here we need to bind the data to our view, there is currently no Data!
//We need to get the data from our JSON
//Parameters is a ViewHolder and a Position
//This gives us the current information object from the whole arraylist
//data.get(position) data is the arraylist and we are getting the current position or index;
//That current obj is of Type QuestionData
QuestionData currentObj= data.get(position);
//we are accessing the Inflated view, or saved view with holder
//holder.answerText is the textView in holder. We are then taking that current object
//We are getting the text of the current object and setting it to the AnswerText view
holder.answerText.setText(currentObj.getMtext());
holder.answerId.setText(currentObj.getId());
holder.mVotes.setText(currentObj.getVotes());
holder.mLikeButton.setTag(currentObj);
}
#Override
public int getItemCount() {
return data.size();
}
public class ViewQuestion extends RecyclerView.ViewHolder{
//once we create it once the reclycer view will automatically recycle it
private TextView answerText;
private TextView answerId;
private TextView mVotes;
private LikeButton mLikeButton;
public ViewQuestion (View itemView){
super(itemView);
//here we are finding the views by their ID
answerText=(TextView)itemView.findViewById(R.id.answerText);
answerId=(TextView)itemView.findViewById(R.id.answerId);
mVotes=(TextView)itemView.findViewById(R.id.VoteTextView);
mLikeButton= (LikeButton)itemView.findViewById(R.id.heart_buttons);
mLikeButton.setOnLikeListener(new OnLikeListener() {
#Override
public void liked(LikeButton likeButton) {
Voting vote = new Voting();
vote.onUpVote(convertToString(),
getAdapterPosition(),ViewQuestion.this);
System.out.print("Adapter Position"+getAdapterPosition());
}
#Override
public void unLiked(LikeButton likeButton) {
Voting onDown=new Voting();
onDown.onDownVote(convertToString(),
getAdapterPosition(), ViewQuestion.this);
}
});
}
public String getVoteView(){
String voteView=mVotes.getText().toString();
return voteView;
}
public String convertToString(){
String converted=answerId.getText().toString();
return converted;
}
public int convertToInt(){
String converted=answerId.getText().toString();
int ConvertedInt=Integer.parseInt(converted);
return ConvertedInt;
}
}
}
When the data that is to be set in RecyclerView is changed, the Adapter needs to get notified of the data change so that it can change the data in recyclerview.
The method
notifyItemRangedChanged(fromIndex,toIndex);
is used to notify the adapter that some set of data is changed among the whole data and it tells the adapter that adapter should refresh the data and reload it into the recyclerView starting from fromIndex to toIndex as passed into the method .
use this method if you have multiple data changed but not all , those changed data also are in cluster so that you can say from 5th to 10th index data are changed .
If all data are changed call :
notifyDataSetChanged();
if only one dataItem is changed then call :
notifyItemChanged(dataPosition);
Using notifyItemRangeChanged(0, this.data.size()) it’s bad practice.
Best way is using notifyItemChanged or notifyItemRangeChanged with payload.
Payload - optional parameter (key). That give you opportunity to check what kind of update do you need.
public void onBindViewHolder(/*...*/, List payloads) {
if (payloads.isEmpty()) {
setText(holder, position);
downloadBitmap(holder, position);
} else if (payloads.contains(SET_ONLY_TEXT)){
setText(holder, position);
}
}
In this example payloads used for checking when adapter should update only the text.
in your case you are not doing it(notifyItemRangeChanged) right as you might as well can call notifyDataSetChanged(); because you are telling the adapter that the entire list has changed and not specific position.
I have a RecyclerView with an TextView text box and a cross button ImageView. I have a button outside of the recyclerview that makes the cross button ImageView visible / gone.
I'm looking to remove an item from the recylerview, when that items cross button ImageView is pressed.
My adapter:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> implements View.OnClickListener, View.OnLongClickListener {
private ArrayList<String> mDataset;
private static Context sContext;
public MyAdapter(Context context, ArrayList<String> myDataset) {
mDataset = myDataset;
sContext = context;
}
#Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_text_view, parent, false);
ViewHolder holder = new ViewHolder(v);
holder.mNameTextView.setOnClickListener(MyAdapter.this);
holder.mNameTextView.setOnLongClickListener(MyAdapter.this);
holder.mNameTextView.setTag(holder);
return holder;
}
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mNameTextView.setText(mDataset.get(position));
}
#Override
public int getItemCount() {
return mDataset.size();
}
#Override
public void onClick(View view) {
ViewHolder holder = (ViewHolder) view.getTag();
if (view.getId() == holder.mNameTextView.getId()) {
Toast.makeText(sContext, holder.mNameTextView.getText(), Toast.LENGTH_SHORT).show();
}
}
#Override
public boolean onLongClick(View view) {
ViewHolder holder = (ViewHolder) view.getTag();
if (view.getId() == holder.mNameTextView.getId()) {
mDataset.remove(holder.getPosition());
notifyDataSetChanged();
Toast.makeText(sContext, "Item " + holder.mNameTextView.getText() + " has been removed from list",
Toast.LENGTH_SHORT).show();
}
return false;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mNumberRowTextView;
public TextView mNameTextView;
public ViewHolder(View v) {
super(v);
mNameTextView = (TextView) v.findViewById(R.id.nameTextView);
}
}
}
My layout is:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="center_vertical"
android:id="#+id/layout">
<TextView
android:id="#+id/nameTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="18sp"
android:padding="5dp"
android:background="#drawable/greyline"/>
<ImageView
android:id="#+id/crossButton"
android:layout_width="16dp"
android:layout_height="16dp"
android:visibility="gone"
android:layout_marginLeft="50dp"
android:src="#drawable/cross" />
</LinearLayout>
How can I get something like an onClick working for my crossButton ImageView? Is there a better way? Maybe changing the whole item onclick into a remove the item? The recyclerview shows a list of locations that need to be edited. Any technical advice or comments / suggestions on best implementation would be hugely appreciated.
I have done something similar.
In your MyAdapter:
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
public CardView mCardView;
public TextView mTextViewTitle;
public TextView mTextViewContent;
public ImageView mImageViewContentPic;
public ImageView imgViewRemoveIcon;
public ViewHolder(View v) {
super(v);
mCardView = (CardView) v.findViewById(R.id.card_view);
mTextViewTitle = (TextView) v.findViewById(R.id.item_title);
mTextViewContent = (TextView) v.findViewById(R.id.item_content);
mImageViewContentPic = (ImageView) v.findViewById(R.id.item_content_pic);
//......
imgViewRemoveIcon = (ImageView) v.findViewById(R.id.remove_icon);
mTextViewContent.setOnClickListener(this);
imgViewRemoveIcon.setOnClickListener(this);
v.setOnClickListener(this);
mTextViewContent.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View view) {
if (mItemClickListener != null) {
mItemClickListener.onItemClick(view, getPosition());
}
return false;
}
});
}
#Override
public void onClick(View v) {
//Log.d("View: ", v.toString());
//Toast.makeText(v.getContext(), mTextViewTitle.getText() + " position = " + getPosition(), Toast.LENGTH_SHORT).show();
if(v.equals(imgViewRemoveIcon)){
removeAt(getPosition());
}else if (mItemClickListener != null) {
mItemClickListener.onItemClick(v, getPosition());
}
}
}
public void setOnItemClickListener(final OnItemClickListener mItemClickListener) {
this.mItemClickListener = mItemClickListener;
}
public void removeAt(int position) {
mDataset.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, mDataSet.size());
}
Edit:
getPosition() is deprecated now, use getAdapterPosition() instead.
first of all, item should be removed from the list!
mDataSet.remove(getAdapterPosition());
then:
notifyItemRemoved(getAdapterPosition());
notifyItemRangeChanged(getAdapterPosition(), mDataSet.size()-getAdapterPosition());
if still item not removed use this magic method :)
private void deleteItem(int position) {
mDataSet.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, mDataSet.size());
holder.itemView.setVisibility(View.GONE);
}
Kotlin version
private fun deleteItem(position: Int) {
mDataSet.removeAt(position)
notifyItemRemoved(position)
notifyItemRangeChanged(position, mDataSet.size)
holder.itemView.visibility = View.GONE
}
The Problem
RecyclerView was built to display data in an efficient and responsive manner.
Usually you have a dataset which is passed to your adapter and is looped through to display your data.
Here your dataset is:
private ArrayList<String> mDataset;
The point is that RecyclerView is not connected to your dataset, and therefore is unaware of your dataset changes.
It just reads data once and displays it through your ViewHolder, but a change to your dataset will not propagate to your UI.
This means that whenever you make a deletion/addition on your data list, those changes won't be reflected to your RecyclerView directly. (i.e. you remove the item at index 5, but the 6th element remains in your recycler view).
A (old school) solution
RecyclerView exposes some methods for you to communicate your dataset changes, reflecting those changes directly on your list items.
The standard Android APIs allow you to bind the process of data removal (for the purpose of the question) with the process of View removal.
The methods we are talking about are:
notifyItemChanged(index: Int)
notifyItemInserted(index: Int)
notifyItemRemoved(index: Int)
notifyItemRangeChanged(startPosition: Int, itemCount: Int)
notifyItemRangeInserted(startPosition: Int, itemCount: Int)
notifyItemRangeRemoved(startPosition: Int, itemCount: Int)
A Complete (old school) Solution
If you don't properly specify what happens on each addition, change or removal of items, RecyclerView list items are animated unresponsively because of a lack of information about how to move the different views around the list.
The following code will allow RecyclerView to precisely play the animation with regards to the view that is being removed (And as a side note, it fixes any IndexOutOfBoundExceptions, marked by the stacktrace as "data inconsistency").
void remove(position: Int) {
dataset.removeAt(position)
notifyItemChanged(position)
notifyItemRangeRemoved(position, 1)
}
Under the hood, if we look into RecyclerView we can find documentation explaining that the second parameter we pass to notifyItemRangeRemoved is the number of items that are removed from the dataset, not the total number of items (As wrongly reported in some others information sources).
/**
* Notify any registered observers that the <code>itemCount</code> items previously
* located at <code>positionStart</code> have been removed from the data set. The items
* previously located at and after <code>positionStart + itemCount</code> may now be found
* at <code>oldPosition - itemCount</code>.
*
* <p>This is a structural change event. Representations of other existing items in the data
* set are still considered up to date and will not be rebound, though their positions
* may be altered.</p>
*
* #param positionStart Previous position of the first item that was removed
* #param itemCount Number of items removed from the data set
*/
public final void notifyItemRangeRemoved(int positionStart, int itemCount) {
mObservable.notifyItemRangeRemoved(positionStart, itemCount);
}
Open source solutions
You can let a library like FastAdapter, Epoxy or Groupie take care of the business, and even use an observable recycler view with data binding.
New ListAdapter
Google recently introduced a new way of writing the recycler view adapter, which works really well and supports reactive data.
It is a new approach and requires a bit of refactoring, but it is 100% worth switching to it, as it makes everything smoother.
here is the documentation, and here a medium article explaining it
Here are some visual supplemental examples. See my fuller answer for examples of adding and removing a range.
Add single item
Add "Pig" at index 2.
String item = "Pig";
int insertIndex = 2;
data.add(insertIndex, item);
adapter.notifyItemInserted(insertIndex);
Remove single item
Remove "Pig" from the list.
int removeIndex = 2;
data.remove(removeIndex);
adapter.notifyItemRemoved(removeIndex);
Possibly a duplicate answer but quite useful for me. You can implement the method given below in RecyclerView.Adapter<RecyclerView.ViewHolder>
and can use this method as per your requirements, I hope it will work for you
public void removeItem(#NonNull Object object) {
mDataSetList.remove(object);
notifyDataSetChanged();
}
I tried all the above answers, but inserting or removing items to recyclerview causes problem with the position in the dataSet. Ended up using delete(getAdapterPosition()); inside the viewHolder which worked great at finding the position of items.
The problem I had was I was removing an item from the list that was no longer associated with the adapter to make sure you are modifying the correct adapter you can implement a method like this in your adapter:
public void removeItemAtPosition(int position) {
items.remove(position);
}
And call it in your fragment or activity like this:
adapter.removeItemAtPosition(position);
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private Context context;
private List<cardview_widgets> list;
public MyAdapter(Context context, List<cardview_widgets> list) {
this.context = context;
this.list = list;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(this.context).inflate(R.layout.fragment1_one_item,
viewGroup, false);
return new MyViewHolder(view);
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
TextView txtValue;
TextView txtCategory;
ImageView imgInorEx;
ImageView imgCategory;
TextView txtDate;
public MyViewHolder(#NonNull View itemView) {
super(itemView);
txtValue= itemView.findViewById(R.id.id_values);
txtCategory= itemView.findViewById(R.id.id_category);
imgInorEx= itemView.findViewById(R.id.id_inorex);
imgCategory= itemView.findViewById(R.id.id_imgcategory);
txtDate= itemView.findViewById(R.id.id_date);
}
}
#NonNull
#Override
public void onBindViewHolder(#NonNull final MyViewHolder myViewHolder, int i) {
myViewHolder.txtValue.setText(String.valueOf(list.get(i).getValuee()));
myViewHolder.txtCategory.setText(list.get(i).getCategory());
myViewHolder.imgInorEx.setBackgroundColor(list.get(i).getImg_inorex());
myViewHolder.imgCategory.setImageResource(list.get(i).getImg_category());
myViewHolder.txtDate.setText(list.get(i).getDate());
myViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
list.remove(myViewHolder.getAdapterPosition());
notifyDataSetChanged();
return false;
}
});
}
#Override
public int getItemCount() {
return list.size();
}}
i hope this help you.
if you want to remove item you should do this:
first remove item:
phones.remove(position);
in next step you should notify your recycler adapter that you remove an item by this code:
notifyItemRemoved(position);
notifyItemRangeChanged(position, phones.size());
but if you change an item do this:
first change a parameter of your object like this:
Service s = services.get(position);
s.done = "Cancel service";
services.set(position,s);
or new it like this :
Service s = new Service();
services.set(position,s);
then notify your recycler adapter that you modify an item by this code:
notifyItemChanged(position);
notifyItemRangeChanged(position, services.size());
hope helps you.
String str = arrayList.get(position);
arrayList.remove(str);
MyAdapter.this.notifyDataSetChanged();
To Method onBindViewHolder Write This Code
holder.remove.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Cursor del=dbAdapter.ExecuteQ("delete from TblItem where Id="+values.get(position).getId());
values.remove(position);
notifyDataSetChanged();
}
});
Incase Anyone wants to implement something like this in Main class instead of Adapter class, you can use:
public void removeAt(int position) {
peopleListUser.remove(position);
friendsListRecycler.getAdapter().notifyItemRemoved(position);
friendsListRecycler.getAdapter().notifyItemRangeChanged(position, peopleListUser.size());
}
where friendsListRecycler is the Adapter name
you must to remove this item from arrayList of data
myDataset.remove(holder.getAdapterPosition());
notifyItemRemoved(holder.getAdapterPosition());
notifyItemRangeChanged(holder.getAdapterPosition(), getItemCount());
//////// set the position
holder.cancel.setTag(position);
///// click to remove an item from recycler view and an array list
holder.cancel.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
int positionToRemove = (int)view.getTag(); //get the position of the view to delete stored in the tag
mDataset.remove(positionToRemove);
notifyDataSetChanged();
}
});
make interface into custom adapter class and handling click event on recycler view..
onItemClickListner onItemClickListner;
public void setOnItemClickListner(CommentsAdapter.onItemClickListner onItemClickListner) {
this.onItemClickListner = onItemClickListner;
}
public interface onItemClickListner {
void onClick(Contact contact);//pass your object types.
}
#Override
public void onBindViewHolder(ItemViewHolder holder, int position) {
// below code handle click event on recycler view item.
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onItemClickListner.onClick(mContectList.get(position));
}
});
}
after define adapter and bind into recycler view called below code..
adapter.setOnItemClickListner(new CommentsAdapter.onItemClickListner() {
#Override
public void onClick(Contact contact) {
contectList.remove(contectList.get(contectList.indexOf(contact)));
adapter.notifyDataSetChanged();
}
});
}
In case you are wondering like I did where can we get the adapter position in the method getadapterposition(); its in viewholder object.so you have to put your code like this
mdataset.remove(holder.getadapterposition());
In the activity:
mAdapter.updateAt(pos, text, completed);
mAdapter.removeAt(pos);
In the your adapter:
void removeAt(int position) {
list.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, list.size());
}
void updateAt(int position, String text, Boolean completed) {
TodoEntity todoEntity = list.get(position);
todoEntity.setText(text);
todoEntity.setCompleted(completed);
notifyItemChanged(position);
}
in 2022, after trying everything the whole internet given below is the answer
In MyViewHolder class
private myAdapter adapter;
inside MyViewHolder function initalise adapter
adapter = myAdapter.this
inside onclick
int position = getAdapterPosition()
list.remove(position);
adapter.notifyItemRemoved(position);
I have a simple array of Strings that I was displaying in a horizontal ListView with an ArrayAdapter. What I'm looking to do is: when the user selects an item from the ListView, make that item not clickable and change the background color of that item. Perhaps like a "grayed-out" look to it. I was looking into creating a custom Adapter and overriding the isEnabled(int position) method but I don't know how I would go about this. Any advice, suggestions, or help will be greatly appreciated thanks!
I was looking into creating a custom Adapter and overriding the isEnabled(int position) method but I don't know how I would go about this.
This is quite easy to do. I recommend a SparseBooleanArray to track the enabled items for efficiency:
public class MyAdapter extends ArrayAdapter<String> {
private SparseBooleanArray enabledItems = new SparseBooleanArray();
public MyAdapter(Context context, int textViewResourceId, List<String> objects) {
super(context, textViewResourceId, objects);
}
#Override
public boolean areAllItemsEnabled() {
return false;
}
#Override
public boolean isEnabled(int position) {
return enabledItems.get(position, true);
}
public void toggleItem(int position) {
boolean state = enabledItems.get(position, true);
enabledItems.put(position, !state);
}
}
The AutoComplete feature of Eclipse did must of the work, but here are some quick notes:
You must override areAllItemsEnabled() along with isEnabled()
I designed toggle() to be used by an onItemClickListener() you only need to call adapter.toggle(position)
If you want to change the row's appearance (more than what enabling and disabling does by default) simply override getView(). Don't forget to cover both cases:
public View getView(int position, View convertView, ViewGroup parent) {
convertView = super.getView(position, convertView, parent);
if(!isEnabled(position)) {
/* change to disabled appearance */
}
else {
/* restore default appearance */
}
return convertView;
}
Hope that helps!
pass position to adapter class when you click on list item
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
adapter.setSelectedIndex(position);
}
add method of setSelectedIndex to adapter class
public void setSelectedIndex(int ind)
{
selectedIndex = ind;
notifyDataSetChanged();
}
Now check the postion of this listview if same then enable and disable value in getView me method
if(selectedIndex!= -1 && position == selectedIndex)
{
holder.tv.setBackgroundColor(Color.BLACK);
}
else
{
holder.tv.setBackgroundColor(selectedColor);
}
holder.tv.setText("" + (position + 1) + " " + testList.get(position).getTestText());
Reference from here
Use setEnabled(bool) property:
yourlistview.setEnabled(false);
Not sure whether it will work or not
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// your code
view.setBackgroundColor(Color.BLUE);
view.setEnabled(false);
}
My vision is to create a color coded listView, where I want to have a slim colored bar in each item's layout. This bar should be a certain color based on an int I pass to the activity. How do I create such a bar(essentially a filled rectangle) and set its color. Currently, I am using a custom layout for my list and using a SimpleAdapter with an ArrayList.
I know I will have to use
if (integerForColor == someNumber)
//set the color of the shape, bar
I am sure this is a simple thing that I simply cannot think of at the moment, or must be missing a fundamental. Thank you in advance for your effort.
EDIT 1:
Trying to decode some of the answers that were here, I realized that you guys need my code on how I am building my list:
public class AddScreen extends Activity implements OnClickListener,
OnItemClickListener, OnItemLongClickListener {
SimpleAdapter adapter;
List<HashMap<String, String>> painItems = new ArrayList<HashMap<String, String>>();
ListView listthings;
public void onCreate(Bundle savedInstanceState) {
from = new String[] { "row_1", "row_2" };
to = new int[] { R.id.row1, R.id.row2 };
adapter = new SimpleAdapter(this, painItems, R.layout.mylistlayout,
from, to);
listthings.setAdapter(adapter);
}
I have added the getView() Method:
public View getView (int position, View convertView, ViewGroup parent){
convertView.setBackgroundColor(R.drawable.red);
return convertView;
//I have no inflater as of now...
}
EDIT 2: As per #huntsfromshadow 's suggestion, I have created a new activity and overridden the getView() method there.
//Imports
public class Adapter extends SimpleAdapter{
public Adapter(Context context, List<? extends Map<String, ?>> data,
int resource, String[] from, int[] to) {
super(context, data, resource, from, to);
// TODO Auto-generated constructor stub
}
#Override
public View getView(int position, View convertView, ViewGroup parent){
View row = convertView;
row.setBackgroundColor(0xFF0000FF);
return row;
}
}
Unfortunately, it still does not work.
Assuming you have everything else setup,
it's probably easiest to define your colored backgrounds in xml like so (red.xml):
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:startColor="#DD0000"
android:endColor="#EE0000"
android:angle="270" />
</shape>
And then use it like this:
context.getResources().getColor(R.drawable.red).
You'll have to pass in and save a context object from the parent Activity.
Look at the answer I gave on how to create a ListView (yes it's parsing data from JSON - ignore that) here
Create a custom adapter and override getView. That is the point where you can do any complicated layout decisions based on values and logic.
A google search for custom adapter will give you a lot of resources.
As #CaspNZ said, use .xml shape files.
In your code extend a 'ListAdapter' (probably either BaseAdapter or ArrayAdapter). Override the getView function like this:
public View getView (int position, View convertView, ViewGroup parent){
if (convertView == null){
//assuming you already have inflater initilized somewhere
convertView = inflater.inflate(you_layout_file.xml, parent, false);
}
//some logic to determine what color the background should be
convertView.setBackgroundDrawable(R.drawable.the_file_you_want_to_use.xml)
}
I hacked together something very similar to color code the text of each item differently. You could adapt it pretty easily to change the color of a bar instead.
Since each element in the list has a different color, you have to remember which color is associated with which location in the array. I just used a simple integer array as a member of my ColorItemsAdapter.
private class ColorItemsAdapter extends ArrayAdapter<String>
{
/*
* For each line to be added to the log, the text is stored in "items"
* and the text color is stored in "colors"
*/
ArrayList<String> items = new ArrayList<String>();
ArrayList<Integer> colors = new ArrayList<Integer>();
int length = 0;
public ColorItemsAdapter(Context context, int textViewResourceId, List<String> stringObj)
{
super(context, textViewResourceId, stringObj);
if(stringObj != null)
{
length = stringObj.size();
}
}
/**
* Adds an item to the adapter, and specifies what color the item should be
* #param item
* The text to be added
* #param color
* The color of the text to be added
*/
public void add(String item, Integer color)
{
items.add(item);
colors.add(color);
length++;
super.add(item);
}
/**
* Adds an item to the adapter at position <i>index</i>
* #param item
* The text to be inserted
* #param index
* The index at which to insert the text
* #param color
* The color of the text to be inserted
*/
public void insert(String item, int index, Integer color)
{
items.add(index, item);
colors.add(index, color);
length++;
super.insert(item, index);
}
/*
* Changes the color of the TextView appropriately before calling the super
*/
public View getView(int position, View convertView, ViewGroup parent)
{
TextView v = (TextView) convertView;
if (v == null)
{
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = (TextView) vi.inflate(R.layout.log_list_item, null);
}
/*
* Here I am setting the text color
* but you could set some other attribute instead.
*/
v.setTextColor(colors.get(position));
return super.getView(position, v, parent);
}
}
Then, to add an item to your list (in this case a red one), you could just use
myColorItemsAdapter.insert(message, 0, Color.RED);
So I had my listview working perfectly then I decided to add a context menu. As soon as I did that whenever I normal clicked an item in my listview, the entire list gets inverted on the first click. Subsequent clicks do nothing to the order, but when the first item is de-selected again the list returns to normal. When I take out the context menu logic that I added, the list view problem does not go away.
I've attached a debugger and the elements in my list adapter are never reordered, and the ListView itself is never set to reverse with .setStackFromBottom()
Here is my onClick listener registered to handle the click events of the list view items:
public void onClick(View v) {
ViewHolder holder = (ViewHolder) v.getTag();
CheckBox b = holder.box;
Boolean check = b.isChecked();
b.setChecked(!check);
if (!check) {
mChecked.add(holder.fu);
if (mChecked.size() == 1) {
buttonLayout.setVisibility(View.VISIBLE);
}
} else {
mChecked.remove(holder.fu);
if (mChecked.size() == 0) {
buttonLayout.setVisibility(View.GONE);
}
}
}
The viewholder class just holds references to objects I use in the listview for optimizations. I cannot figure out why this is causing my list to invert when displayed, I've tried moving the listener to a different view in the layout, I've tried re-writing the listener, nothing seems to work! Any advice would be appreciated.
Edit: here is the code for the view holder
/** Class to provide a holder for ListViews. Used for optimization */
private class ViewHolder {
TextView date;
TextView gallons;
TextView cost;
TextView cpg;
TextView mpg;
CheckBox box;
FillUp fu;
}
as well as the adapter:
public class FillUpAdapter extends BaseAdapter {
ArrayList<FillUp> mElements;
ArrayList<FillUp> mChecked;
Context mContext;
public FillUpAdapter(Context c, ArrayList<FillUp> data) {
mContext = c;
mElements = data;
mChecked = new ArrayList<FillUp>();
}
public void clearChecked() {
mChecked.clear();
}
public ArrayList<FillUp> getChecked() {
return mChecked;
}
public boolean remove(FillUp f) {
mChecked.remove(f);
return mElements.remove(f);
}
#Override
public int getCount() {
return mElements.size();
}
#Override
public Object getItem(int arg0) {
return mElements.get(arg0);
}
#Override
public long getItemId(int arg0) {
return mElements.get(arg0).getId();
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LinearLayout layout;
ViewHolder holder;
if (convertView != null) {
layout = (LinearLayout) convertView;
holder = (ViewHolder) layout.getTag();
} else {
layout = (LinearLayout) LayoutInflater.from(mContext).inflate(
R.layout.fillup_list_item, parent, false);
holder = new ViewHolder();
holder.cost = (TextView) layout
.findViewById(R.id.fillUpListTotalValue);
holder.cpg = (TextView) layout
.findViewById(R.id.fillUpListCostPerGal);
holder.gallons = (TextView) layout
.findViewById(R.id.fillUpListGalValue);
holder.mpg = (TextView) layout
.findViewById(R.id.fillUpMPGText);
holder.date = (TextView) layout
.findViewById(R.id.fillUpListDate);
holder.box = (CheckBox) layout
.findViewById(R.id.fillUpListCheckBox);
holder.fu = (FillUp) getItem(position);
layout.setTag(holder);
}
holder.date.setText(holder.fu.getDate());
holder.gallons.setText(holder.fu.getGallonsText());
holder.cpg.setText(holder.fu.getCostText());
holder.cost.setText(holder.fu.getTotalText());
holder.mpg.setText(String.format("%03.1f MPG",holder.fu.getMPG()));
if (convertView != null) {
holder.box.setChecked(mChecked.contains(holder.fu));
}
layout.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
ViewHolder holder = (ViewHolder) v.getTag();
CheckBox b = holder.box;
Boolean check = b.isChecked();
b.setChecked(!check);
if (!check) {
mChecked.add(holder.fu);
if (mChecked.size() == 1) {
buttonLayout.setVisibility(View.VISIBLE);
}
} else {
mChecked.remove(holder.fu);
if (mChecked.size() == 0) {
buttonLayout.setVisibility(View.GONE);
}
}
}
});
return layout;
}
}
UPDATE:
Ok, so I've narrowed it down to the visibility change on the buttonLayout view, which is a linear layout of buttons on the bottom of the Activity's layout, underneath the ListView. Whenever I change that view's visibility to View.VISIBLE (which happens when the first item is checked) the list's order is reversed. The order is restored when the view's visibility is set to View.GONE
I have no idea what would cause that though :(
After narrowing the scope a bit more, I discovered the problem was not the changing of the visibility of my button bar, but actually the passing around of FillUp objects in holder.fu of my ViewHolder class. By changing that to instead reference the adapter's getItem(position) method, everything seemed to work out. Quite an odd bug, since the adapter itself was not having the order of the elements changed, but passing around a reference to the object made it very unhappy.
If your listview background color changes when you click on it, I think it is about your theme. Just play with the cache color parameters of your listview, here is an example:
<ListView
android:layout_width="fill_parent"
android:id="#android:id/list"
android:scrollingCache="true"
android:persistentDrawingCache="all"
android:cacheColorHint="#0000"
android:layout_height="wrap_content"
android:fastScrollEnabled="true"
android:stackFromBottom="true"
android:smoothScrollbar="true"
android:paddingTop="115dip">
</ListView>