Develop Reference

Saving state of UI in Android

I'm making a to-do list app and after user presses the button I create a new GridLayout(and all the data about time and name of the task inside of it) and add it into my RelativeLayout. How do I save those GridLayouts in UI so after the activity is destroyed and launched again those layouts are there.
After pressing the button I trigger the Create Activity method
public void CreateActivity(String name,int hours, int minutes,int i)
{
RelativeLayout.LayoutParams relparams= new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.WRAP_CONTENT);
relparams.addRule(RelativeLayout.BELOW,i);
relparams.setMargins(0,50,0,100);
Glayouts.add(new GridLayout(this));
Glayouts.get(i+1).setBackgroundColor(Color.GRAY);
Glayouts.get(i+1).setMinimumWidth(relative.getWidth());
Glayouts.get(i+1).setId(i+1);
Glayouts.get(i+1).setPadding(10,0,0,0);
GridLayout.LayoutParams namee = new GridLayout.LayoutParams();
namee.columnSpec = GridLayout.spec(0);
namee.rowSpec = GridLayout.spec(0);
namee.setGravity(Gravity.LEFT);
final TextView Actname = new TextView(this);
Actname.setText(name);
GridLayout.LayoutParams checkbox = new GridLayout.LayoutParams();
checkbox.columnSpec = GridLayout.spec(1);
checkbox.rowSpec = GridLayout.spec(0);
checkbox.setGravity(Gravity.RIGHT);
CheckBox check = new CheckBox(this);
// ADDING TO LAYOUT
Glayouts.get(i+1).addView(Actname,namee);
Glayouts.get(i+1).addView(check,checkbox);
relative.addView(Glayouts.get(i+1),relparams);

Theoretically when you extends View, then you can also override onSaveInstanceState and onRestoreInstanceState methods, where you must provide your own SavedState class that typically extends BaseSavedState. You can find info on that here
In your case, your layout is dynamic, therefore this doesn't really work. To tell you the truth, your layout probably shouldn't be constructed this way, you should be rendering the grid using a RecyclerView based on a "model" that describes this layout, render the items of the grid via the RecyclerView.Adapter, and you should persist either the "model", or the data you use to construct this model along with the user-inputted state so that you can re-construct the model that will be rendered via your RecyclerView.
You can read more about RecyclerView here.
You can read more about data persistence here.
You can read about using onSaveInstanceState to save data in Activities/Fragments across config change and process death (but not finishing then restarting the app) here.

You can’t. The best way to save state is to use some persistence mechanism, for example database (I’d recommend Room as it is officially supported by Google).
After clicking a button, you should put all the needed information (name, hours, minutes) in the database and when Activity is created, you can read all persisted data and - basing on it - create all needed layouts again.
Another option is storing data in SharedPreferences - it is much easier to setup, so you can also start with this solution. Please note, I'm suggesting it as a first step in the world of persistency in Android, not as a preferred solution for storing data.

RecyclerView doesn't refresh after modifying database's row

I am programming an app for Android. I uploaded it to GitHub: app
I have a ViewPager (MainActivity.java) controlling two Fragments. On the first Fragment (FirstFragment.java) you can add People (People.java) which appears on the RecyclerView (also on FirstFragment.java). When you click one of the list items on the RecyclerView its details (name and id) appear on the second fragment (SecondFragment.java). The SecondFragment.java also contains a button you can delete the selected People with.
To store the People objects I used a List of People and managed it with the methods in PeopleLab.java. The program was working fine: I could add/remove People objects to the list and it appeared on the RecyclerView fine.
After that, I decided to replace the List with a database. It only meant creating the database (the 3 files in database folder) and editing the already existing and two new methods in PeopleLab.java. The other files remained untouched.
The database is working as expected (checked it with sqlite3), I can add/remove People like before and the queries work. My only problem is that the changes don't appear on the RecyclerView. But if I close and reopen the app, the changes appear.
It's like the RecyclerView doesn't care about the database in runtime, only do when the app starts (or closes, not sure).
Do you have any idea what could cause the problem? My only guess is I miss something about how Android apps handle databases.
P.S.: sorry for my English.

You do call notifyDataSetChanged() on the adapter but you don't provide any new data for that adapter.
In your FirstFragment :
private void updateUI() {
PeopleLab peopleLab = PeopleLab.get(getActivity());
List<People> peoples = peopleLab.getPeople();
if(mAdapter == null) {
mAdapter = new PeopleAdapter(peoples);
mRecyclerView.setAdapter(mAdapter);
} else {
// You actually have to change your dataset
mAdapter.changeDataSet(peoples);
}
}
And in your Adapter :
public void changeDataSet(List<People> people) {
this.mPeoples = people;
notifyDataSetChanged();
}
This some brutal way to do it though.
It would be better to notify your adapter on insertion / removal calling notifyItemInserted(int itemPosition) or notifyItemRemoved(int itemPosition). (And refreshing your dataset, by the way)

It will not work automatically.You can either use to notify the adapter the underlying data has been changed so that adapter can fetch and reload the data.It can be done using adapter.notifyDataSetChanged()
Or use can use CursorLoader to achieve the same

Android: Adding accessibility to a custom view

I'm attempting to implement accessibility on a few custom views for an Android app.
I've condensed what is done in the Google Authenticator app with no luck:
public class CardView extends RelativeLayout {
// ...
#Override
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
event.setClassName(this.getClass().getName());
event.setPackageName(this.getContext().getPackageName());
event.getText().add("Card Test");
return true;
}
}
All TalkBack reports back is "Double-tap to select" when it's inside a ListView or ViewPager.
Does ViewPager override accessibility events?
What do I need to do in order to have TalkBack say "Card Test" inside ViewPagers and ListViews like I expect it to?

For current versions of Android, you need to set the content description of the view.
myView.setContentDescription("Card Test");

ListView and associated classes expect you to use the onItemSelectedListener instead of assigning an onClickListener to each View (and rightfully so).

If incorporating alanv's suggestion, try to convince android system to read out the content description
by either
If(accessibilityModeIsEnabled())//custom method that checks context.getSystemService(Context.ACCESSIBILITY_SERVICE).isEnabled()
myView.sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_HOVER_ENTER);
or AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED.
or requestFocus
Above should done when myView is visible. May be during onMesasure when width and height are both positive
If list view is still unable to do so, then try doing the above tricks on the first element of list view. Accessibility in Android varies devices to device and not one strategy fits all

Adapter for a custom layout of listview

I am developing an android project in which I have to load from group of String arrays(say title,description,id) to the listview item TextView.
I did something similar with a database using a cursor like this
String[] from = new String[]{"medicine","healthsystem"};
int[] to = new int[] {R.id.textlist1,R.id.textlist2};
// Now creating an array adapter and set it to display using my row
SimpleCursorAdapter notes =new SimpleCursorAdapter(this,R.layout.notes_row, c, from, to);
I listed all the targets in "from" and all the origin in "to".
Now my problem is I don't have a database so cant use a cursor.
I have 3 arrays of strings which i want to load into textviews(title,description,id) of each item
How to do this
Please kindly help me out
thank you :)

If you don't have a cursor, why are you using a SimpleCursorAdapter?
Read this article about creating a SimpleListView using SimpleAdapter for alternate ideas.

There are lots of examples of populating lists from various data sources in the ApiDemos project that comes with the Android SDK - browse through those, and you should find one that fits what you're trying to do.

First of all you need to create a Class that holds that information, something like:
public class StringHolder{
String titte;
String description;
int id;
}
Then you create the layout of your row that says where you want your title, your description and your image.
Then you create an Adapter. The adapter will hold your data and will say for each position in the list what information should be loaded.
At last you need to use your adapter in an activity.
For more information you can see a tutorial here: http://www.softwarepassion.com/android-series-custom-listview-items-and-adapters/

android listview pagination implementation

Hi am working on an android application. And am using a listview in some of my activities.
The problem is all of my listviews displayed are much longer so that the user needs to scroll the whole list to go for the last item.
Am trying to implement a pagination for this, like at first say only 20 items need to displayed on the listview. And at the end of my listview i need a titlebar which have next & previous buttons and on clicking on next button the listview will load the next records from 21st to 40 and so on.
Am using java rest webservice to load the listview.
Can anyone give me a good suggestion for solving my problem.?

Solution 1:
You can load all the data at once if its not TOO MUCH, store it locally & then you can navigate in that locally stored data. Define some variables like StartPoint & EndPoint & get the desired data from that stored data. Increment decrement the values of StartPoint & EndPoint by using the PreviouButton & NextButton.
Solution 2:
Get only the desired data from your data source for example 10 records each time when a Navigation button is clicked.

I suggest than you load list data in a custom Adapter class that extends BaseAdapter class. Like #oriolpons suggested, you should add a footer view, and when you click on button next call some method that is fetching next for example 20 rows, and then add them in your adapter object and call notifyDataSetChanged().
For example
private OnClickListener mListener = new OnClickListener() {
public void onClick(View v) {
ArrayList<YourObject> al = getSomeData(int startRow, int endRow);
MyCustomAdapter adapter = new MyCustomAdapter();
for(YourObject a : al)
adapter.add(a);
getListView.setAdapter(adapter);
notifyDataSetChanged();
}
};
Hope this helps.

The easiest solution is to add a footer view to the listview. And on the item click listener you can see if it is the last position (load more items), or not
//add the footer before adding the adapter, else the footer will not load!
View footerView = ((LayoutInflater)this.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listfooter, null, false);
this.getListView().addFooterView(footerView);

#Tijo . Refer this site http://www.androidhive.info/2012/03/android-listview-with-load-more-button/. You can have a button which would call the execute method of Async task and that will load the remaining list for you.