We Keep Coding

How to make the holder in if else statements of onClick method work without final in argument Viewholder in arguments of onBindViewHolder method

I am trying to make a text change when a button located along with the text (layoutPasswd) in recycler view and to change it back if the button is again pressed.Like a password hiding button. The values to the adapter is from a static class object as arraylist. The problem occurring now is that the value for all the items (only for layoutPasswd) in recycler view is same.
public void onBindViewHolder(#NonNull final viewHolder holder, int position) {
holder.layoutUName.setText(users.get(position).getUserName());
pos = position;
holder.layoutPasswd.setText("********");
holder.btnViewChanger.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (holder.view1) {
holder.layoutPasswd.setText(users.get(pos).getPasswd());
holder.btnViewChanger.setText("hide");
holder.view1 = false;
} else {
holder.layoutPasswd.setText("********");;
holder.btnViewChanger.setText("Show");
holder.view1 = true;
}
}
});

You cannot rely on the ViewHolders or Views in a RecyclerView to hold any state, because they are recycled. Every time a view scrolls onto the screen, first it calls your onBindViewHolder function to update the contents of that ViewHolder to match the data.
Any configuration you set on the views or the ViewHolder instance in onBindViewHolder cannot be relied on to stay the same if the view scrolls off the screen, because the original ViewHolder might be recycled to be used for some other data, and when it scrolls back on screen, you might be looking at some other view that has been recycled from other data that just scrolled off the screen.
So if your views have configuration that you want to "stick", you have to back it up when you change it, and restore it in onBindViewHolder. The way you accomplish this will depend on how you are managing the data that you pass to the adapter.
If you can modify your User class, you can add a Boolean to it that stores whether it should show the password. Then in your onBindViewHolder, you restore the state based on this Boolean. And you also update this Boolean when the state changes.
I also updated the way the click listener works to simplify it for toggling. I removed the pos = position line, because almost certainly that is not something you should be doing.
public void onBindViewHolder(#NonNull final viewHolder holder, int position) {
final User user = users.get(position)
holder.layoutUName.setText(user.getUserName());
holder.layoutPasswd.setText(user.isShowPassword() ? user.getPasswd() : "********");
holder.btnViewChanger.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
user.setShowPassword(!user.isShowPassword());
holder.layoutPasswd.setText(user.isShowPassword() ? user.getPasswd() : "********");
holder.btnViewChanger.setText(user.isShowPassword() ? "hide" : "show");
}
});
// ...
}
If you cannot modify the User class, this is more complicated. Then the adapter should have its own ArrayList<Boolean> to store the state by position index, but you need to keep this list at least as long as the data that is bound, and reset everything to false if the whole list of data is refreshed.

How to get child views of listview item from outside the adapter

I want to thank you in advance for the solution to my question.
I have a custom adapter for my listview. the list item has an imageView(1), a progressBar(3), and a download button(2).
When the download button for each list item is clicked, I grab vital details of the listitem such as the position of the view, the resourceid of the button, the resource id of imageview and the resource id of progress bar, then i make an parcealable object of class "Download".
Download download = new Download();
download.setUrl(url);
download.setButtonResource(this.downloadBt.getId());
download.setCreativeWork(creativeWork);
download.setDownloadBt(this.downloadBt);
download.setProgressBarResource(this.progressBar.getId());
download.setProgressBar(this.progressBar);
download.setContext(activity);
download.setViewResource(view.getId());
Intent intent = new Intent(activity, BroadcastService.class);
intent.putExtra("download", download);
Log.e("download button", url);
activity.startService(intent);
I start a service which does the download and reports back using a broadcast. When this broadcast message is received I want to update the progress bar.
My problem is how to get the progress bar concerned from my mainactivity which receives the message. How do I reference this?
I am currently using a parcelable object to pass the resource id for the progressbar, all the way from the adapter to the service, then to the receiving activity(mainActivity) using the intent's putExtra(), then I do this at the mainActivity
Download download = (Download)intent.getParcelableExtra("download");
ProgressBar progressBar = (ProgressBar)findViewById(download.getProgressBarResource());`
The issue here is that always only returns the first item of the list, regardless of which listitem is clicked. I would want to get each unique listitem and update the progress bar and the download button. Thanks

I am assuming that you show this layout in a ListView or RecyclerView. First thing that need to do is, add a field for index in your Download class to identify the position in the list from where that button was pressed. Next, pass the index from your getView() or onBindViewHolder() to the function that creates the Download object and add that index to the object.
When you receive the when you broadcast any update from your Service, do include the index value. Now, in your code in your activity where you receive the broadcast value, extract the value of index and the progress. Now, you could write something like this to update the progress of that view in the list:
int index = ... //some value you received in broadcast
int progress = ...//some value you received in broadcast
View view = listView.getChildAt(index);
if (view != null) {
ProgressBar progressBar = (ProgressBar) view.findViewById(R.id.progressBar);
if (progressBar != null) {
progressBar.setProgress(progress);
}
}

This can be one of the solution to your problem
First You need to pass progress value to the adapter that may be zero in start.
Implement setOnItemClickListener for your listview
listView.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
final int position, long id) {
//now point to your item position and do your stuff here
}
});
When ever you receive broadcast for download progress. Just update your ListView by Nullifying previous items with new items containing download progress values.

Not sure if this is what you looking for...
In you adapter. do below.. (I take a sample from my project which do a delete card from the list, when the delete button is clicked)
In getView function inside adapter.
Card card = list.get(position);
viewHolder.imgDelete.setTag(card);// --> i set the whole card info to tag
outside the adapter.
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
int id = v.getId();
if (id == R.id.iv_delete_card) {
//System.out.println("---> Card: " + tag);
//delete card
Object tag = v.getTag();
if (tag != null && tag instanceof Card) {
promptDeleteCard((Card) tag);
}
}
}

Items of RecyclerView are not showing correctly

In my onBindViewHolder of my RecyclerView.Adapter<SearchAdapter.ViewHolder> when user clicks on cardview a button becomes visible. But when I'm scrolling recyclerview some other items buttons are shown as visible too. Why is this happening?
this is my code:
#Override
public void onBindViewHolder(final ViewHolder viewHolder, final int position) {
viewHolder.card.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (viewHolder.content_layout.getVisibility() == View.VISIBLE) {
viewHolder.content_layout.setVisibility(View.GONE);
viewHolder.address.setMaxLines(2);
viewHolder.attribute.setMaxLines(2);
} else {
viewHolder.content_layout.setVisibility(View.VISIBLE);
viewHolder.address.setMaxLines(8);
viewHolder.attribute.setMaxLines(8);
}
}
});
...
}

Once you start scrolling down the list your views get recycled. This means a previously inflated ViewHolder (some that gets created in onCreateViewHolder) is reused.
So what you have to do is to remember the clicked positions (e.g. via a SparseBooleanArray) and check in onBindViewHolder whether the view should be visible (previously clicked) or not.
You can find a basic usage example of the SparseBooleanArray in this StackOverflow post

The 'other' visible items buttons are the ones using the same viewholder that was modified in the callback. So because viewholders (and views) are recycled :
They should only store information that can be retrieved each time the viewholder is bound to a position.
Anything that may be changed in the views state should be refreshed in onBindViewHolder()
In your case you should store the 'is selected' somewhere else and reset the visibility and maxlines in onBindViewHolder() (not only in the callback)

Good idea is to make a class object with all data you need for one item in recycler view, also add there one boolean isItemWasClicked and inside onBindViewHolder() check this boolean and make buttons visible or not.
For example:
public class OneItemOfList{
int priceToDisplay;
String name;
String date;
boolean wasClicked;
}
public class YourAdapter extends RecyclerView.Adapter<OneItemOfList.ViewHolder> {
ArrayList<OneItemOfList> items;
...
#Override
public void onBindViewHolder(ViewHolder viewHolder, final int position) {
viewHolder.view.setText(items.get(position).name);
if (items.get(position).wasClicked)
viewHolder.button.setVisible(View.VISIBLE);
else
viewHolder.button.setVisible(View.GONE);
viewHolder.view2.setOnClickListener(...
OnClick(...){
items.get(position).wasClicked = !items.get(position).wasClicked;
});
}
...
}

create an array for example Boolean array, and when each position clicked, set true in same position of array. and in onBindViewHolder check if that array[position] is true set that item visible if.

Drag and Drop in a `ListView`

I am trying to implement a drag and drop in a ListView in android(Ice Cream Sandwich). So when the dragged object reaches the edge of the ListView, I am scrolling the ListView in the relevant direction. The problem is that when we scroll, sometimes the adapter creates new Views as necessary and these 'new' Views did not receive the ACTION_DRAG_STARTED event earlier and hence do not receive the DragEvent updates. Is there any way I can send the events to these views as well?

An easiest way to implement drag and drop in listview is you use this great library.
https://github.com/commonsguy/cwac-touchlist
it's worth trying.

Looking at the source for View, I see:
static final int DRAG_CAN_ACCEPT = 0x00000001;
int mPrivateFlags2;
boolean canAcceptDrag() {
return (mPrivateFlags2 & DRAG_CAN_ACCEPT) != 0;
}
mPrivateFlags2 is package-private and not exposed by the SDK. However, you should be able to change it in a subclass by doing:
try {
Field mPrivateFlags2 = this.getClass().getField("mPrivateFlags2");
int currentValue = mPrivateFlags2.getInt(this);
mPrivateFlags2.setInt(this, currentValue | 0x00000001);
} catch (Exception e) {
}

I have the same problem. I did not solved this recycling problem, but I found a possible workaround still using the Drag & Drop framework. The idea is to change of perspective: instead of using a OnDragListener on each View in the list, it can be used on the ListView directly.
Then the idea is to find on top of which item the finger is while doing the Drag & Drop, and to write the related display code in the ListAdapter of the ListView. The trick is then to find on top of which item view we are, and where the drop is done.
In order to do that, I set as an id to each view created by the adapter its ListView position - with View.setId(), so I can find it later using a combination of ListView.pointToPosition() and ListView.findViewById().
As a drag listener example (which is, I remind you, applied on the ListView), it can be something like that:
// Initalize your ListView
private ListView _myListView = new ListView(getContext());
// Start drag when long click on a ListView item
_myListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
view.startDrag(null, shadowBuilder, _myListView.getItemAtPosition(position), 0);
return true;
}
});
// Set the adapter and drag listener
_myListView.setOnDragListener(new MyListViewDragListener());
_myListView.setAdapter(new MyViewAdapter(getActivity()));
// Classes used above
private class MyViewAdapter extends ArrayAdapter<Object> {
public MyViewAdapter (Context context, List<TimedElement> objects) {
super(context, 0, objects);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View myView = convertView;
if (myView == null) {
// Instanciate your view
}
// Associates view and position in ListAdapter, needed for drag and drop
myView.setId(position);
return myView;
}
}
private class MyListViewDragListener implements View.OnDragListener {
#Override
public boolean onDrag(View v, DragEvent event) {
final int action = event.getAction();
switch(action) {
case DragEvent.ACTION_DRAG_STARTED:
return true;
case DragEvent.ACTION_DRAG_DROP:
// We drag the item on top of the one which is at itemPosition
int itemPosition = _myListView.pointToPosition((int)event.getX(), (int)event.getY());
// We can even get the view at itemPosition thanks to get/setid
View itemView = _myListView.findViewById(itemPosition );
/* If you try the same thing in ACTION_DRAG_LOCATION, itemView
* is sometimes null; if you need this view, just return if null.
* As the same event is then fired later, only process the event
* when itemView is not null.
* It can be more problematic in ACTION_DRAG_DROP but for now
* I never had itemView null in this event. */
// Handle the drop as you like
return true;
}
}
}
Now if you need to have a visual feedback when doing a drag and drop, there are several strategies. You can for instance have 2 instance variables in your activity named:
private boolean ongoingDrag = false; // To know if we are in a drag&drop state
private int dragPosition = 0; // You put the itemPosition variable here
When doing the drag and drop in MyListViewDragListener you modify these variables, and you use their state in MyViewAdapter. Of course do not forget to update the UI (in the event thread of course, use a Handler) with something like _myListView.getAdapter()).notifyDataSetChanged() or maybe _myListView.invalidate() method.

The problem is because listView.getPositionForView(view) returns -1 if the view is not visible when it is called. So relying on that will fail when you scroll the list. So, instead of setting a view.setOnLongClickListener() you can set a listView.setOnItemLongClickListener() on the list item which calls startDrag() on the item. onItemLongClick() gives you the position which you can pass to in the myLocalState parameter of startDrag(). Then you recover that in onDrag() using event.getLocalState() and casting it to an Integer. Like this...
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
position -= listView.getHeaderViewsCount();
DragShadowBuilder dragShadow = new View.DragShadowBuilder(view);
view.startDrag(null, dragShadow, position, 0);
return true;
}
});
Then in your OnDragListener...
#Override
public boolean onDrag(View eventView, DragEvent event) {
Integer dragViewPos = ((Integer) event.getLocalState());
int eventViewPos = listView.getPositionForView(eventView) - listView.getHeaderViewsCount();
...
}

How can I update multi select in android dialog window

I have been unable to find a tutorial helping with multi-selects using cursors. As of right now my logic is working the way I want but the check boxes will not update properly. What am I overlooking?
return new AlertDialog.Builder(this).setTitle("Items")
.setMultiChoiceItems(cur, CHECK, EDATE, new DialogInterface.OnMultiChoiceClickListener() {
#Override
public void onClick(DialogInterface dialog, int position, boolean checked)
{
DBM.open();
AlertDialog AD = (AlertDialog) dialog;
ListView list = AD.getListView();
list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
itemCur = (Cursor) list.getItemAtPosition(position);
if (checked)
{
//update query
DBM.setChecked(checkCur.getInt(checkCur.getColumnIndex(ID)), itemId, userId, 1);
list.setItemChecked(1, true);
} else
{
DBM.setChecked(checkCur.getInt(checkCur.getColumnIndex(ID)), itemId, userId, 0);
list.setItemChecked(1, false);
}
DBM.close();
}
}).setPositiveButton("OK", new DialogButtonClickHandler()).create();

Dialogs on android can't be modified. If you look at the source code you will see that dialogbuilder delegates all the presentation work to some components and you don't have access to them after creation. Thus changing the state of the components you use for building the dialog won't update the dialog components afterwards.
You can see this mechanism here and here : you don't have access to the access controller after onCreate has been called on the alert controller.
The best if you want to achieve this is to rebuild a new activity and give it a dialog theme.

You can just use the setCursor() method for AlertDialog. Its pretty simple so you probably wouldn't need a tutorial.
A relevant SO questions is here and the docs for it are here

So after digging into the issue a bit and going through a couple different iterations I finally found a solution that I am fairly happy with. With school and work pushing hard I have had little time outside to work on extra projects and I have been sitting with this solution for while now but unable to get it posted.
The final piece to my puzzle was finding the changeCursor function, this fixed the issue of the old data that no longer matched the DB to load. My current hurdle is the time it takes to check a box, there is an obvious lag from clicked to updated. I have found that mutliple records update when one is clicked. I have not been able to find a valid reason for these extra updates.
Below is the code I currently have implemented to have the multi-select working. This just the dialog code, for a working demo I will be posting a project on GitHub for a working prototype of it all in action. (Now made public, Multiselect Dialog)
I am a fairly new Android developer, majority of my Android knowledge has been self taught and learned through the knowledge of online resources. I was working on a school project and wanted to implement a multiselect in a dialog that would update the main activity with the selected choices. Please lend any advice you can on how to improve this.
Pros:
- Populates check boxes properly on load.
- Updates database when check is clicked.
- Keeps display updated after data change.
Cons:
- Must click check box to update value.
- Unable to undo changes made while in dialog. The values save onClick, I have not been able to think of a way to temporarily store the new values until confirmed by the user.
- A single click updates multiple records, also sometimes when choices scroll off the screen values update
#Override
protected Dialog onCreateDialog(int id)
{
switch (id) {
case 0:
LayoutInflater factory = LayoutInflater.from(this);
// Setup of the view for the dialog
final View bindListDialog = factory.inflate(R.layout.multi_list_layout, null);
multiListView = (ListView) bindListDialog.findViewById(R.id.multiList);
// Because I do not know how to properly handle an undo in this situation
// I make the dialog only close if the button is pressed and confirms the changes
return new AlertDialog.Builder(MultiSelectDemoActivity.this).setTitle(R.string.multiSelectTitle)
.setCancelable(false).setView(bindListDialog)
.setPositiveButton(R.string.btnClose, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton)
{
updateItemList(); // In my implementation there is a list view
// that shows what has been selected.
}
}).create();
default:
return null;
}
}
private static final boolean ONCREATE = true;
private static final boolean ONUPDATE = false;
private void setupMultiList(Boolean newList)
{
demoDBM.open();
multiCur = demoDBM.getList(userId); // Gets all items tied to the user.
startManagingCursor(multiCur);
// Uses the cursor to populate a List item with an invisible ID column,
// a name column, and the checkbox
demoDBM.close();
if (newList)
{
// Creates a new adapter to populate the list view on the dialog
multiAdapter = new SimpleCursorAdapter(this, R.layout.check_list_item, multiCur, new String[] { DemoDBM.ID,
DemoDBM.NAME, DemoDBM.SEL }, new int[] { R.id.itemId, R.id.itemName, R.id.itemCheck });
multiAdapter.setViewBinder(new MyViewBinder());
multiListView.setAdapter(multiAdapter);
} else
{
// updates the previously made adapter with the new cursor, without changing position
multiAdapter.changeCursor(multiCur);
}
}
#Override
protected void onPrepareDialog(final int id, final Dialog dialog, Bundle args)
{
setupMultiList(ONCREATE);
}
public class MyViewBinder implements ViewBinder
{
#Override
public boolean setViewValue(View view, Cursor cursor, int columnIndex)
{
int checkId = cursor.getColumnIndex(DemoDBM.SEL);
if (columnIndex == checkId)
{
CheckBox cb = (CheckBox) view;
// Sets checkbox to the value in the cursor
boolean bChecked = (cursor.getInt(checkId) != 0);
cb.setChecked(bChecked); // Switches the visual checkbox.
cb.setOnCheckedChangeListener(new MyOnCheckedChangeListener());
return true;
}
return false;
}
}
public class MyOnCheckedChangeListener implements OnCheckedChangeListener
{
#Override
public void onCheckedChanged(CompoundButton checkBox, boolean newVal)
{
View item = (View) checkBox.getParent(); // Gets the plain_list_item(Parent) of the Check Box
// Gets the DB _id value of the row clicked and updates the Database appropriately.
int itemId = Integer.valueOf(((TextView) item.findViewById(R.id.itemId)).getText().toString());
demoDBM.open();
demoDBM.setChecked(itemId, userId, newVal);
demoDBM.close();
setupMultiList(ONUPDATE);
}
}