(FYI, I'm targeting 2.2 Froyo in my project, so any solution would have to work at that build level.)
What I want to do seems quite simple; show a list of items in a ListView, and allow the user to tap to select multiple items before performing an operation on all of them at once.
To provide a little more detail, I am binding a ListView to an array of objects. The screen consists of other controls, with the ListView in the middle. Each list item has several components; two images, and a text label. NO checkbox. Instead, when the user taps an item, the background should change to indicate that it is checked. If the item is tapped again, the background should change back to indicate it is not checked. The user may tap one or more items. If the user scrolls the list off the screen and scrolls it back, the state of those items should be preserved.
From what I've researched, I gather that I need to:
use a Drawable as the background for the list items with selectors for checked, pressed and default states
create a custom class extending LinearLayout or RelativeLayout and implementing Checkable, then use this as the root View for the list item layout
I've found several tutorials online, but none work. Either they have runtime errors, or simple don't do anything... pressing the buttons does not change their appearance to checked.
I found an alternative approach in the O'Reilly "Android Cookbook." Rather than doing all of the above, they add a boolean to the objects the ListView is bound to, then manually add code to change that boolean when a list item is clicked and to change the background in the adapter for an item where the boolean is true. In other words, they don't use Checkable at all. This does not seem like an ideal solution to me; abandoning the Android API in favor of custom hacks often seems to cause bugs later on, and I'm uncomfortable with adding GUI information (whether or not an item is selected) to what should be a purely data-carrying POJO conceptually representing a chunk of information.
My question is this: does anyone have a WORKING tutorial to accomplish what I have described, using Android's Checkable functionality? Or is this so problematic that something like the O'Reilly hack always has to be used?
I have never read Android Cookbook but their strategy is exactly what I would do. I would decline to call this a hack and suggest this is the kind of thing that the Android framework intends to do. A selected state in my opinion is part of the model you wish to protect, I do see how it could be in a gray area as it removes the purity of your POJO's.
There is a second strategy you could use to protect the purity of your POJO's use the state of the background to find if something is selected or not. Additionally you could also use a plain color resource instead of a drawable background.
Related
I would like to start by saying if you can think of a better title for this problem, feel free to change it since I have no clue how to explain this in a short way.
So here is my problem:
For the application I am trying to make I have these schedules, one schedule for today, and one for upcoming days. Both of these are a listview inside a fragment.
(I used those fragments to create tabs to seperate the two.)
Each game (let's call them games because calling them activities would be confusing) on the schedule has a status, and here is where the annoying part comes. I have been asked to check if any game has been started, and if so I need to disable the buttons to start any other game than the one that is already ongoing.
EDIT: The main problem is that I cannot use findViewById on the listview item because apparently it is a null object reference
I made a little "paint"ing to give you more of a graphical representation.
So long story short, I need a way to check the status inside of every listview item inside of the listview inside of the fragment inside the activity to use said status to disable every button except for the one of the ongoing game.
Little side note: If no games have been started yet, all buttons are enabled.
I hope this made sense.
If you want some code to go with this, feel free to ask but be warned, I am making this inside a testing app so a lot of useless testing data and sloppy code.
EDIT:
This is where I am stuck in a more clear example:
The start buttons are enabled but should be disabled.
Scrolling further down the list, there is a started 'game' and right below it, a game with the same status as in the previous picture where the button is disabled as it should be.
This is because the "isStartable" boolean in my code goes to false after the game with status "start" has passed and the following items are disabled.
When I scroll back up, it is how it should be, the items are all disabled but I need them to be like this when the listview gets filled. Any way to refresh the data in this listview and taking the "isStartable" boolean with it?
This is what it looks like after I scroll back up.
create a model class for your listview data items. Set a boolean variable in model class like isGameStarted. Set that variable as per your result.Then in your listview adapter, put a condition as below
if(isGameStarted){
holder.startButton.setEnable(true);
else
holder.startButton.setEnable(false);
I'm using Recyclerview to show a list. I want to delete some items like IOS. In my listview template I have added a button to delete item which is invisible by default. In my activity I have another button attached at bottom (Not part of listview) and on tap of this button I want to make all delete buttons of listview visible.
My Question is how can I get reference to all delete buttons of listview in activity and is it the right way to do this?
Thanks
Assuming you have ViewHolders set up, you already have references to all the buttons in your list. All you have to do is to make them visible for every item in the list with a simple loop.
In case you haven't implemented ViewHolders I suggest you check out the documentation and take a look at some simple tutorials on how to use them.
On a side note. If I understood correctly you're making a bottom tab for your app and since you referenced iOS I gotta say this; Remember that Android and iOS are two unique operating systems with their own ways of handling things. Check out Googles pure Android documentation.
In your question title you say RecyclerView, but in your text you say ListView. The solution is similar either way, but it's best to be perfectly clear what you're doing.
In either case, there are at least two different solutions.
First, you could use a boolean flag to determine if all the the item buttons should be showing or not. You check this flag at the time the item view is inflated or created and toggle the button accordingly. If the boolean flag is ever changed, the easiest thing to do is tell the RecyclerView/ListView that the underlying data has changed and to redraw all the views. Call notifyDatasetChanged on the adapter.
The other thing you can do at the time the item buttons should change is iterate all the visible item views, find the button, and change its visibility. With RecyclerView, you can do this, and with ListView you can do this.
I'm not averse to rolling my own, but wanted to make sure I'm not overlooking pre-existing functionality.
I need a ListView where each View can take a highlighted state and then be un-selected by virtue of selecting a different item in the list. Basically a radio list.
I totally understand how to build one myself, so please don't jump down my throat with "what have you tried"... I'm just asking if I'm overlooking a pre-built tool already baked into the Android toolkit.
Either add attribute android:choiceMode=singleChoice in layout.
or,
call setChoiceMode(AbsListView.CHOICE_MODE_SINGLE) on ListView from your code.
If you need item views to highlight on selection, use android.R.layout.simple_list_item_activated_1 or android.R.layout.simple_list_item_activated_2 for item layout.
I was looking for a ListPreference in which the user can change the order of items from a list. The items would be draggable and can be re-ordered by the user.
I saw this in my custom ROM (and I'm almost sure I saw it in Cyanogenmod) for the QuickPanel. Here's a screenshot to get the idea through:
I know how I can make custom ListView items and set the icon to indicate that the items are draggable, but I don't know how to make them draggable, and change the order accordingly. As for saving them in the preferences, I found this which could be implemented easily.
PS: I know Cyanogenmod is open-source, but I couldn't find the source for this particular thing :( The closest I could get was this, which should be somewhere near the other screen...
Thanks in advance for any tip about this.
UPDATE: I ended up using the files from the accepted answer, with additions and modifications. I am listing them here for further reference.
Use a custom Adapter (ArrayAdapter in my case), to implement the visual feedback that this item is draggable, which is an ImageView near the TextView. This is optional.
Set a DragListener and RemoveListener to update the list accordingly. The ListView does not do that automatically. And it depends on the Adapter you are using.
There was a line that casted a View to a ViewGroup, it made some errors, so I removed the cast without any issue, it was not needed. (in the onInterceptTouchEvent method).
Change mRemoveMode = 1; in the constructor of TouchInterceptor, or one of: FLING = 0; SLIDE = 1; TRASH = 2;. I think for TRASH, a resource should be available too.
I actually took the file not from the answer's link but from the Cyanogenmod one, which I already had, but I guess these files were the same.
These are the actual files in the project (at r12, at the time of writing):
The Preference using this ListView
The ListActivity with the listeners and the Adapter
The actual ListView
I hope it helps somebody else :)
There is no built-in widget to do this, but you may want take a look at the custom implementation used by the AOSP music player to allow for re-ordering of songs in playlists.
TouchInterceptor.java
That's the class which is extending ListView and is responsible for handling all of the MotionEvents and re-ordering its items, as well as detecting swipes for deleting items. You can see it implemented into an activity here in the TrackBrowserActivity.java class.
It has three interfaces you should also be aware of: DragListener, DropListener, and RemoveListener. You can use these interfaces to provide it callbacks to fire for those events, so that you can update changes made to the list order to your SavedPreferences (since the ListView will not handle that for you).
You can easily extend or modify the TouchInterceptor class to add additional functionality since the low-level stuff is all there for you.
I have a ListView backed by customized ArrayAdapter where each item has 2 LinearLayouts - one I call head, and the other one - body.
The body is hidden (gone) until user clicks on the row at which time it slides out. The second click (on the head) will hide the body. However if user clicks on the body it brings another activity. All of this works just fine, here comes the problem:
When user presses on body I want a visual indication of the action just the same way as regular list item will flicker an orange background when pressed. I'm not getting this by default since (my theory) the onPress event is intercepted by body's view and not processed by the list item.
The first thing I tried was to execute body.setBackground('#ff00ff') (never mind the color) in onPress event. That didn't work since (I suspect) there's no repainting after the call. Then I dig a little bit more and decided to use <selector/>-based background. I defined body_background.xml in drawable folder and assigned that to the body's background property.
There I noticed that background will only change if the even is processed by the list. For example if I set <item android:state_selected="true" android:drawable="#drawable/selected"/> then when I press on the head - the background of both elements (head and body) will change, however when I press on body - nothing.
So to summarize my question - how do I change background of the child element in the list item if I assign custom onClick handler to it? Any hints will be greatly appreciated
OK. Here's some more info I dig along the way.
I'm currently trying to switch implementation to ExpandableListView which provides the functionality I had to coded in (sliding body). The problem I may have here is that I have a fancy "endless" list implementation and I'm using ArrayAdapter#add method to dynamically add items to the list while scrolling (see my tutorial on androidguys.com) Well, the add method is missing from the BaseExpandableListAdapter so I need to see if adding items to internal array will work (it didn't for ArrayAdapter) possibly doing ExpandableListView#notifyChanged() will take care of that
The fact that I don't see anything when I'm directly using setBackgroundColor method is probably due to the subsequent call to startActivity call that halts all painting until new Activity is displayed
P.S. this has been resolved by switching to ExpandableListView. And may I add - it's beautiful! No need to invent anything