I am working on an Android app which will support the Ice cream sandwich API but work on older devices such as running android 2.1.
I'm doing this by doing a check of what the current API version is, and if its post ice cream sandwich call one activity and then if its anything below, call a different activity.
I am allowing the user to perform a search, when it gets the results it then clears ArrayList and then adds the items from the search back in, and then calls the arrayadapter.notifydatasetchanged. This code I've copied and pasted from the ICS version into the pre ICS version, the ICS works fine but on the pre ics version the list view doesn't get updated. Below is the code that I have.
public void performSearch(ArrayList<Spanned> searchPasswords)
{
if (searchPasswords.size() > 0)
{
btnClearSearch.setVisibility(View.VISIBLE);
passwords.clear();
for (int i = 0; i < searchPasswords.size(); i++)
{
passwords.add(searchPasswords.get(i));
}
passwordArrayAdapter.notifyDataSetChanged();
btnClearSearch.setOnClickListener(mBtnClearSearch);
common.showToastMessage(searchPasswords.size() + " result(s) found", Toast.LENGTH_LONG);
}
else
{
common.showToastMessage("No search results found", Toast.LENGTH_LONG);
}
}
I've debugged this function so it is definetely calling it, and its displaying the toast messags with saying how many results were found, but the list view doesn't get changed.
Update
I have just made a discovery which is a bit confusing. As a test in the function that does the initial loading of the list view I manually create a new search ArrayList<Spanned> and pass this to the same PerformSearch(ArrayList<Spanned>) that I am having the problem with and this works without any problems.
The problem with the performSearch not updating the ListView only seems to happen when it is being called from onActivityResult. I know that onActivityResult is working fine as when the performSearch function is called it then prints out there is 1 result(s) found so its definitely got data just the list view doesn't get refreshed from the onActivityResult calling the performSearch function.
You can try:
passwordArrayAdapter = new WHAT_EVER_ADAPTER_THIS_IS(searchPasswords, extra_constructor_params);
YOUR_LIST_VIEW.setAdapter(passwordArrayAdapter)
instead of:
passwordArrayAdapter.notifyDataSetChanged();
I had a similar issue. Neither notidfyDataSetChanged() nor setAdapter() worked.
Finally I figured out a solution which may not be as efficient as using notifyDataSetChanged() but it works.
/**
* Updates courses' list adapter.
*/
private void updateListAdapter()
{
final ArrayAdapter a = (ArrayAdapter) coursesList.getAdapter();
runOnUiThread(new Runnable()
{
public void run()
{
populteCoursesList();
a.clear();
for (MainScreenListModel model : listModels)
{
a.add(model);
}
a.notifyDataSetChanged();
}
});
}
courseList is my custom list. populateCoursesList() gets the data from db and listModels is a Vector of models for list view.
As you can see I have to clear the adapter and fill it once again.
I think your mistake is to forget to clear the adapter, if you try it like this it should work:
public void performSearch(ArrayList<Spanned> searchPasswords)
{
if (searchPasswords.size() > 0)
{
btnClearSearch.setVisibility(View.VISIBLE);
passwordArrayAdapter.clear();
for (int i = 0; i < searchPasswords.size(); i++)
{
passwordArrayAdapter.add(searchPasswords.get(i));
}
passwordArrayAdapter.notifyDataSetChanged();
btnClearSearch.setOnClickListener(mBtnClearSearch);
common.showToastMessage(searchPasswords.size() + " result(s) found", Toast.LENGTH_LONG);
}
else
{
common.showToastMessage("No search results found", Toast.LENGTH_LONG);
}
}
passwords.clear();
for (int i = 0; i < searchPasswords.size(); i++)
{
passwords.add(searchPasswords.get(i));
}
passwordArrayAdapter.notifyDataSetChanged();
As per the code, u r modifying the list(passwords), but is it the same instance that is being used by the adapter (passwordArrayAdapter). If not then notifyDataSetChanged() wont work.
From my understanding, you can either set the list again with a new instance of passwordArrayAdapter.
ur_list_view.setAdapter(new PasswordArrayAdapter(newly_formed_password_list, and other parameters));
or use getter and setter to update the list(passwords) and then call notifyDataSetChanged()
I dont know much from only the code snippet you've pasted but from what I see there is no persistent link between passwords and the passwordsArrayAdapter....passwordsArrayAdapter initialises itself with the elements of passwords and passwordsArrayAdapter will not know when passwords changes. To add new items you should call passwordsArrayAdapter.add(searchPasswords).Dont bother calling notifyDataSetChanged() explicitly.
public void performSearch(ArrayList<Spanned> searchPasswords)
{
if (searchPasswords.size() > 0)
{
btnClearSearch.setVisibility(View.VISIBLE);
passwordArrayAdapter.clear();
passwordArrayAdapter.setNotifyOnChange(true);
for (int i = 0; i < searchPasswords.size(); i++)
{
passwordArrayAdapter.add(searchPasswords.get(i));
}
btnClearSearch.setOnClickListener(mBtnClearSearch);
common.showToastMessage(searchPasswords.size() + " result(s) found", Toast.LENGTH_LONG);
}
else
{
common.showToastMessage("No search results found", Toast.LENGTH_LONG);
}
}
I wouldnt think there'd be a relation with the onActivityResult bit -- the above code should fix it.
Call notifyOnChange(false) before clearing and adding the new entries. Otherwise, the clear() and every add() internally trigger a call to notifyDataSetChanged(), which, as I experienced, confuses the ListView. Keep your explicit notifyDataSetChanged(), which also resets the internal notifyOnChange flag to true again.
Thanks everyone for your help and suggestions, I've managed to find out what the problem was.
In my OnResume method for the activity I call a function called populateListArray which retrieves all of the information from the database and lists in the ListView.
When the activity was returned it was calling the OnResume method so after it got the results it then reset the list view back with all the original content.
To get round it I added a variable called performingSearch which I initialise to false. When I perform the search I set this to true and in the onResume, if the variable is true I don't do anything and after the perform search function has finished I set the variable back to false again.
Thanks everyone again for your help
Related
Last week I started learning Android as I needed to create an application for one of the projects at Uni.
The application is a simple barcode/QRcode scanner and it should scan the code, compare its result with the database (I'm using Firebase) and either return other data from database if the barcode is found or ask the user if he wants to add the barcode to the database if it's not found.
I thought the easiest way to do it would be to use AlertDialog, but the app crashes every single time I scan the code.
I debugged the app and checked the Logcat, what I get is:
You need to use a Theme.AppCompat theme (or descendant) with this activity.
This is exactly where I get the error and where I wanted to use AlertDialog - based on the value in the variable details.
private BarcodeCallback callback = new BarcodeCallback() {
#Override
public void barcodeResult(final BarcodeResult result) {
barcodeView.decodeSingle(callback);
dbRef.child("Items").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> item = dataSnapshot.getChildren().iterator();
Boolean isFound = false;
while (!isFound || item == null) {
DataSnapshot i = item.next();
String check = i.child("ID").getValue().toString();
if (result.getText().equals(check)) {
isFound = true;
details = "Consumption: " + i.child("Consumption").getValue().toString()
+ "\nCost: " + i.child("Cost").getValue().toString()
+ "\nName: " + i.child("Name").getValue().toString();
} else {
details = "Not found";
}
}
new AlertDialog.Builder(getApplicationContext())
.setMessage("This is just an example for the purpose of the question.")
.create()
.show();
}
I get the error exactly on the line with .show();.
In the previous posts I found that you can't display AlertDialog in this place, and you need to use runOnUiThread function or Handler, none of those options worked for me, and I was getting the error in the same place.
Do you guys have any advice or suggestions?
Also, I'm sorry for the way this post looks like or for any missing but required information. I know it's not an excuse, but this is my first post here.
Thanks in advance for any replies.
The problem is here:
new AlertDialog.Builder(getApplicationContext())
You can't build a Dialog using the application context. To reach this you need an Activity Context.
Read this question or this article for further understanding
I am trying to perform some task based on the data retrieved from Firebase.
for (inti=0;i<dateList.size();i++)
{
attendanceDateRef= attendanceRef.child(dateList.get(i));
attendanceClassRef= attendanceDateRef.child(ViewAttendanceSelectClassActivity.selectedClass);
attendanceClassRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshotdataSnapshot) {
for (DataSnapshotdsp : dataSnapshot.getChildren())
{
attendanceList.add(dsp.getValue(String.class));
Log.e("attendanceListValues",dsp.getValue(String.class));
}
}
#Override
public void onCancelled(DatabaseErrordatabaseError) {
}
});
}
intindex=1;
for (inti=1;i<=attendanceList.size();i++)
{
if(i%4==0)
{
fullDateRangeList.add(dateList.get(index));
index++;
}
else
{
fullDateRangeList.add(dateList.get(index));
}
}
Log.e("fullDateRangeList",String.valueOf(fullDateRangeList.size()));
Log.e("attendanceList",String.valueOf(attendanceList.size()));
above code is written on the OnClick event of a Button , when I click on the Button following output is generated on logcat:
fullDateRangeList:0
attendanceList:0
attendanceListValues:Value1
attendanceListValues:Value2
attendanceListValues:Value3
attendanceListValues:Value4
.
.
.
attendanceListValues:ValueN
from the above output it looks like second loop is executing before data is retrieved from Firebase and that is why size of fullDateRange and attendanceList is 0.
is there any way i can prevent second loop from executing until data is stored in attendanceList?
You cannot stop that method or make it wait until you get the all the data from your database. This is the behaviour of an asynchronous method. You need to change the logic of your code a little bit by declaring and using that data only inside the onDataChange() method, otherwise it will be always empty.
Also there is another approach. If you want, you can dive into the asynchronous world and use my answer from this post.
I create an app with Firebase. There is an issue that i can't solve, and didn't find it talked here.
In this method I want to check if some data is already in the server. If not - I want to add it (the code of adding works well. The Firebase database is being changed as I want). so I'm using onDataChange method as following:
public boolean insertNewList(String title)
{
System.out.println("start: ");
final boolean[] result = new boolean[1];
result[0]=false;
final String group = title;
mRootRef = some reference...
mRootRef.addValueEventListener(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
System.out.println(0);
if (dataSnapshot.child(group).getValue() != null)
{
System.out.println(group + " is already exist");
System.out.println(1);
}
//write the data.
else
{
mRootRef=mRootRef.child(group);
mRootRef.push().setValue("some data");
System.out.println(2);
result[0]=true;
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
});
System.out.println(3);
return result[0];
}
But what realy happens is this output:
begin:
3 (just skip on onDataChange method and return false).
some print after calling the function
0 (goes back to function and enter to onDataChange method)
2 (finally goes where I want it to go)
0 (for some reason enters twice :( )
1
And because of that i receive wrong results in this function.
Can you help please?
Replace
mRootRef.addValueEventListener(new ValueEventListener()
with
mRootRef.addListenerForSingleValueEvent(new ValueEventListener()
When you add the the value to firebase, "addValueEventListener" called again, not like addListenerForSingleValueEvent that shots only once anywhy.
The output that you showed us looks normal to me. Let me try to explain:
begin: // a) this comes from the System.out.println("begin")
3 // b) you DECLARE your value event listener and then you run
// the System.out.print("3") statement
0 // c) you just added a listener so firebase calls you, and
// your listener fires
2 // d) this is the first time your listener fires, so you go
// into the block called "write the data"
0 // e) since you just wrote the data, firebase calls you again
1 // f) this time, since the data has been written, you go into
// the block called "is alraedy exist"
This is normal behaviour for firebase.
In c), firebase always calls you back one time when you declare a listener.
In e), firebase calls you because the data changed.
But in b), you are only declaring your listener, not yet running it, so the statements after this declaration are executed and you see "3" before anything else happens.
I am using 'ion-infinite-scroll' in html to load more items from server for this i am using below code
<ion-infinite-scroll immediate-check="false" on-infinite="getListOfAreas()" distance="1%">
</ion-infinite-scroll>
Here, getListOfAreas() function is called when I scroll screen to bottom and it fetches data from server.This is getListOfAreas() function defined on controller
$scope.getListOfAreas = function (shoudlShowLoader) {
AreaBusiness.getAreasListing(shoudlShowLoader, function(serviceResponse) {
$scope.$broadcast('scroll.infiniteScrollComplete');
if (serviceResponse != null) {
var isSuccess = serviceResponse.Success;
if (isSuccess) {
}
}
}
}
On browser, i have debugged some how
$scope.$broadcast('scroll.infiniteScrollComplete');
above line of code keeps calling and spinner keep rotating.I don't know the reason. Am I missing anything?
$scope.$broadcast('scroll.infiniteScrollComplete'); only lets ionic know that the current page of data has been fetched and that it's safe to now fetch the next page. This does not indicate that all data has finished loading.
Looks like the official recommendation is to add an ng-if to the scroll delegate and remove it from dom once there is not more data to load.
Example:
<ion-infinite-scroll
ng-if="moreDataCanBeLoaded()"
icon="ion-loading-c"
on-infinite="loadMoreData()">
</ion-infinite-scroll>
Source: https://ionicframework.com/docs/api/directive/ionInfiniteScroll/
I have resolved the issue, after spending sometime. The issue which I found, I was not adding those elements into the list which were to be shown on UI. So, list was not being updated on controller that is why it kept calling.So I updated my code and added those fetched items from service to list associated to ui as mentioned in my below code
$scope.$broadcast('scroll.infiniteScrollComplete');
if (serviceResponse != null) {
var isSuccess = serviceResponse.Success;
if (isSuccess) {
if ($scope.areas != undefined && $scope.areas.length > 0) {
pushDataToPOIList(serviceResponse.PointOfInterestData);
} else {
$scope.areas = serviceResponse.PointOfInterestData;
}
pushDataToVehiclesList() method I added that is pushing new data into list to update list and on UI as well. This helped me to sort out the problem.
I'm working in an app using Parse.com and I've been experiencing some random behavior, I made a simpler version of my code to show you and while it keeps being random (the results I expect happen about 4 in 5 times) it got better (in my code it's correct about 2/5 of the runs).
So the method is this, a very simple creation and filling of a new object:
public void test(){
final List<ParseObject> list = new ArrayList<>();
for(j=0;j<4;j++){
list.add(new ParseObject("Object"));
list.get(j).put("Column1", "sup");
list.get(j).put("Column2", "bro");
if(j==3){
ParseObject.saveAllInBackground(list, new SaveCallback() {
#Override
public void done(ParseException e) {
Toast.makeText(MainActivity.this, "NANANANANANANANA BATMAN!",Toast.LENGTH_LONG).show();
}
});
}
}
}
}
Problem is it creates 4 ParseObjects (as it should) only 4/5 of the tries, then 1/4 it's only 3. Why does this happen?
Why don't you create and store your ParseObject in a variable and then, use put("Column1", "sup"); and put("Column2", "bro"); on it before adding this variable directly to your list? because you are accessing your list two times for nothing where it can be avoided.
It would be cleaner and it would allow you to debug better.