I have views with hundreds layouts (Linears with TextViews), basically it's like list with data.
My presenter after querying the database (sqlbrite, rxjava, its asynchronous) calling method on view which simply create linear with textviews and adds it to some other Linear (its parent for every added view)
With 100+ rows of data on my older phone there is a freeze. How can I reduce it? I can't add views on other thread than UI of course.
First thing you need to use a recycler view for list of views. and ofcoarse you can use 100 different types of views with ViewTypes of recycler view
Second if you insist not to use recycler view then you may better use AsyncTask for adding views at least. Because in some methods of AsyncTask you can access the UI thread and can add elements.
Third possibility is with event bus. you will add a method to the fragment/activity and register it with event bus. make it run in background from the tag(java tags). and call it from background thread for adding items(views)
Hope some of it solve your problem :) if not get back to me with more explanation of the question.
P.S EventBus is a library work almost the same as BroadcastReceivers but it has more features and its more efficient as well.
Related
I am actually developing an Android application on which I should display dynamic forms based on metadata contained inside JSON documents. Basically the way it works (without the details) is that a JSON document represent the structure of a form:
{
"fields": [
{
"name": "fieldA",
"type": "STRING",
"minCharacters": 10,
"maxCharacters": 100
},
{
"name": "fieldB",
"type": "INTEGER",
"min": 10,
"max": 100
},
{
"name": "fieldC",
"type": "BOOLEAN_CHECKBOX",
"defaultValue": true
}
...
],
"name": "Form A"
}
What I'm doing actually when the application receive one of those JSON documents is that it loop through each fields and parse it to the appropriate view (EditText, Checkbox, custom view, etc.), adding a tag to the view (to be able to retrieve it easily) and add the view to a LinearLayout. Here is a pseudo-code of how it is working actually:
//Add form title
linearLayout.addView(new TextView(form.name));
//Add form fields
for(Field field: form.fields) {
View view;
switch(field.type){
case STRING: view = new EditText();
...
}
view.setTag(field.id);
linearLayout.addView(view);
}
The issue with this is that with large forms (like >20 fields), it need to inflate lot of views and the UI thread suffer a lot. Another point to take into account is that a single screen may have multiple forms (one after another vertically sorted).
To avoid overloading the UI thread I thought of 2 possible solutions:
Using a RecyclerView.
Using Litho by Facebook.
But multiple questions comes to me when considering these 2 solutions:
Is it a good use case to use Litho? Or using a RecyclerView is enough?
What about the state of my views? If I use a Recycling pattern, would I be able to keep the state of each of my fields (even those off-screen) and so being able to save the form without losing data?
If I use a Recycling pattern to display one form, how would I handle multiple forms? Can we have nested RecyclerView? Forms need to be displayed one after another like inside a vertical RV but if forms themselves are RV, how should I handle this?
This is more a "good practice" question and giving the right way or one of the right way of achieving my goal than a need of a specific answer with code example, etc.
Thank's in advance for your time.
When architecting for the mobile application I would like to address the following questions:
Is it a good use case to use Litho? Or using a RecyclerView is enough?
Are the views are being recycled properly:
What does it mean to us is consider, creating 40-50 view per screen and as user moves out of the view, system should not mark all views for GC rather it should be inside some kind archived list and as we require it again we should be able to fetch from it.
Why do we need to that: GC is the costliest operation which would cause app rendering to be jitter, we try to minimize the GC to called at this point by not clearing the views
For this I would like to go with litho, justification is here as your requirement seems to have more of variable count of viewtypesreference
Conclusion: Litho +1, RecyclerView +0
What about the state of my views? If I use a Recycling pattern, would I be able to keep the state of each of my fields (even those off-screen) and so being able to save the form without losing data?
Saving EditText content in RecyclerView This is one the component but same logic should be appliced to checkbox or radiobutton as well. or as in state-maintenance for litho is here
Conclusion: Litho +1, RecyclerView +1 both has specific API's to achieve state maintenance
If I use a Recycling pattern to display one form, how would I handle multiple forms? Can we have nested RecyclerView? Forms need to be displayed one after another like inside a vertical RV but if forms themselves are RV, how should I handle this?
This has to be addressed with user experience plus technical capability: As per user behaviour IMHO,I discourage the nested vertical scroll however others were able to achieve it you can easily find on how to in SO. Optimal solution would be to have horizontal scroll within either Andriod's or litho's recycler view as here
NOTE: If you need to know implementation details, please raise it as separate question, I would be happy to help there
UPDATE #1:
The issue with this is that with large forms (like >20 fields), it need to inflate lot of views and the UI thread suffer a lot.
UI creation/layout has to be performed at the backend only adding to the view has to be done on UI thread. And litho does it in-built. However same can be achieved native recycler view as well but you have to move off the UI thread and post periodically to UI.
Ok, you have two separate problems here. One is overwork the UI thread, and the other is to keep the state of your anonymous views. About the first part:
1.-Litho could help you with this. But you have to move all your logic towards litho components instead of android widgets. Since I don't know your codebase, I don't know how hard this can be. A recyclerview would help with view recycling, but that only matters if you are well, using a list.
2.-It could, as long as you have a way to keep a representation of the widget's state that you can pass to the adapter and then back to the view (I'm assuming you generate all the windows by code and then have zero reference to them) and so. It sounds messy, and it is messy, so I won't try it.
3.-You can, but is messy. Best approach in this case would be having horizontal recyclerviews inside a vertical recyclerview. Nesting recyclerviews inside another recyclerview with the same direction creates funny problems, like "Why this cell is not scrolling". I would avoid using the recyclerview as a parent if the view does not need it.
Now, to the solutions:
A) UI Overloading: According to your pseudocode, you aren't inflating stuff. You are creating java objects which happens to be subclasses of View. That's good, because creating objects in a background thread is far easier than inflating (Parsing XML and use it as arguments to generate identical copies of a given resource by invoking constructors) stuff in a background thread. While a LinearLayout context constructor requires an UI thread to be executed, other things, like textviews, don't. So you can create the latter ones inside an asynctask and after you are done generating your whole hierarchy, execute the methods that need the UI thread and add the generated layout to the window. For the view classes that don't support being created as java objects asynchronously, you can have an XML file with just that component, like the linearLayout, and create then asynchronously with the support package asyncLayoutInflater. this solution can be implemented in any codebase and would allow you to make your UI generation completely asynchronous.
B)Keeping track of the view state: Again, I'm assuming your view hierarchy is anonymous. If so, what you need is to generate an interface you can use as a contract to invoke both state saving and state loading from a lifecycle aware component, like the activity. After creating such interface, subclass the widgets and create a subscription/event bus system in each widget that saves/loads the state from the widget every time is triggered. That way, each of of the components on the screen would be able to remember their state while remaining anonymous.
Just use the RecyclerView and create views on runtime (you are not inflating, you are instantiating)
Dynamically creating and adding views should not slow the UI thread considerably on mid-range devices. If it does, do investigate for bottlenecks elsewhere
You can perform a simple benchmark by adding/removing/setting text with lots of views dynamically inside a RecyclerView or even a LinearLayout hosted by a ScrollView, and you'll see it goes smooth
Use jetpack composer provided by android
https://developer.android.com/jetpack/compose
I have a mix of 10-15 custom views and fragments to be shown in a vertical list. I am not sure if RecyclerView has any advantage in scenarios where all views are dissimilar. RecyclerView seems to add lot of boiler-plate code, and I think the only advantage I would get is easier enter/exit animation.
My custom views/fragment also make web-service call on being created. We don't cache web-requests for business reasons. My understanding is that RecyclerView would trigger these web-service calls on each binding, resulting in redundant calls and visible latency. Comparatively ScrollView should load the views once, and it keeps them all in memory, avoiding multiple calls.
Is my understanding correct ? I need some help understanding performance implications with ScrollViews, in the given scenario.
ScrollView
With a ScrollView, all of its subviews will be created at once, regardless of visibility on screen. If using a ScrollView for your solution, you'll probably want to "listen" for when its subviews become visible to update their content, using placeholders initially. You could also build something that will fetch the content in a background thread. This may get more complex than you want very quickly.
RecyclerView
A RecyclerView provides the advantage of deferring creation of child views until they become visible automatically, and can re-use child views with common layouts.
By using different "item view types" for each of your children, you'll disable the "recycling" part of RecyclerView, but still get the benefit of deferring the creation of views until they are scrolled into view.
RecyclerViews do provide a fairly structured pattern for you to work with via the Adapter and ViewHolders. Though not personally familiar with it, RecyclerView also has a RecyclerView.ViewCacheExtension which is intended to give the developer control over caching of views.
Overall, the advantage of late binding (don't create and load views that might never be viewed) and the flexibility of the RecyclerView will probably yield good results for you.
First of all you have to decide what you are using View or Fragment or maybe both. Don't compare View with Fragment there is a common misconception about these two, they are not similar, actually a Fragment is close to an Activity in terms of architecture and implementation.
Second, can you reuse some of these View/Fragment, if yes, then RecycleView can help you a lot.
After you decided about the topics above:
My understanding is that RecyclerView would trigger these web-service
calls on each binding
No, this is not true, the binding method is called whenever a new item is displayed (reused or newly created), you can implement adapter to perform the web API only once on an item, this is your choice.
I always go for RecycleView/ListView whenever possible, it helps to reduce the memory footprint and can reduce the implementation. In some cases, where there is no huge memory usage on views and I can't reuse some of the implementation, then I go for ScrollView, but I think twice before implementing it.
Can i call setcontentview multiple times if my layout is same but the resource changes.for instance if images get exchanged in 2 imageview widgets??(this is infact all that is happening in my app)
You can switch the setContentView several times. However, I have learned in practice, that UI elements don't cross over. In other words each time you set the view, you have to re-findViewById for your UI elements.
You should go for ViewFlipper. Follow this link,it may help you.
Calling setContentView() multiple times
You can "refresh" the ImageViews by calling
myImageView.invalidate();
This will make the view be redrawn. If you're using an AdapterView (such as a ListView) call
myListView.notifyDataSetChanged();
I have an activity with a HorizontalScrollView. When it opens, I start filling this view (or rather, a container layout inside it) with another views. This is done from another thread by using handler.post.
The views are added in bunches of 15, and when there are no more views to add, I start updating them with new data (this is a kind of streaming data from a server).
The problem is that the scrollview is empty until all of the views are added. As soon as they are all added and start updating, the scrollview gets drawn.
How do I refresh it in the process of adding views? I don't want the screen to be empty for 3 seconds while all of the views are added.
Thanks a lot.
UPDATE: turned out this problem is not specific for HorizontalScrollView, this is the case for any generic layout.
Im not sure I understand exactly how your program is constructed, so that the views are not shown until you start updating... but perhaps myLayout.forceLayout() helps?
The thing is ofcourse that layout only gets shown after onCreate().
I could imagine you use a AsyncTask to perform data lookup and use the callbacks provided in that class to update the UI, since they run on the main thread. This way you can just finish the onCreate(), and then start updating your view.
Dynamically I am creating the linear layout and adding the views to linear layout every 5 sec I need to update data to linear layout from database .
But When I checked the log output it is adding to linear layout but gui is not getting updated for every 5 sec. I am using scheduled fixed timer task .
What should i do ?
I agree w/ the other answer from Dimitar that you probably don't want to do this with a linear layout.
However if you must, are you calling invalidate() on the LinearLayout after adding a new view to it?
If you want to visualize data in your application, you should adapt this data to the UI component that will display it. LinearLayout doesn't sound like a good choice for what you are trying to do.
Most often, in Android this is done by using a subclass of BaseAdapter and displaying the data in a subclass of AdapterView. Changes in the adapted data should be handled by the adapter, and the UI component should be updated accordingly.
If you are using SQLite database, take a look at the classes Cursor and CursorAdapter.