Develop Reference

ArrayList and ListView are not being populated

I am completely lost and have no idea why my ListView is not being populated. In my method where I am inserting data into my ArrayList, it says my adapter symbol cannot be resolved, but as far as I know I have properly declared the adapter in my onCreate.
Am I correct in assuming that if I have a ListView inside of my activity, set up an ArrayList that fills my adapter, and then tie that adapter to the ListView that my ListView will auto-populate in my activity whenever the array receives information?
Here are my declarations inside of my onCreate.
ListView listView = (ListView) findViewById(R.id.dispScores);
ArrayList<viewScores> savedScores = new ArrayList<viewScores>();
ScoreAdapter adapter = new ScoreAdapter(this, savedScores);
adapter.setDropDownViewResource(android.R.layout.simple_list_item_1);
listView.setAdapter(adapter);
These are the methods I am using to add data into my ArrayList.
public View.OnClickListener onClickListener = new View.OnClickListener() {
#Override
public void onClick(View view) {
EditText input1 = (EditText) findViewById(R.id.scorePrompt);
TextView output1 = (TextView) findViewById(R.id.textTotal);
String blankCheck = input1.getText().toString(); //CHANGE INPUT IN scorePrompt TO STRING
switch (view.getId()) {
case R.id.buttTotal:
if (blankCheck.equals("")) {
Toast blankError = Toast.makeText(getApplicationContext(), "YOU CANT SKIP HOLES JERK", Toast.LENGTH_LONG);
blankError.show();
break;
} else {
int num1 = Integer.parseInt(input1.getText().toString()); //Get input from text box
int sum = num1 + score2;
score2 = sum;
output1.setText("Your score is : " + Integer.toString(sum));
//ATTEMPTING TO WRITE TO ARRAYLIST
viewScores addScore = new viewScores(input1.getText().toString());
adapter.notifyDataSetChanged();
adapter.add(addScore); //WHY DOESNT THIS WORK?
j++;
input1.setText(""); //Clear input text box
break;
}
case R.id.allScores: //CHANGE THIS TO AN EDIT BUTTON, ADD A HOLE NUMBER COUNTER AT TOP OF SCREEN!!!!!
output1.setText("you messed up");
break;
case R.id.editScore: //Need to set up Save Array before we can edit
//CURRENTLY ONLY DISPLAYS THE LAST NUNMBER IN THE TEXTEDIT, NEED TO SET UP LISTVIEW!!!!!!
for (int i=0; i < j; i++){
// output1.setText(savedScores.get(i));
} break;
}
}
};
public class viewScores {
public String hole;
public viewScores(String holeNum) {
this.hole = holeNum;
}
}
public class ScoreAdapter extends ArrayAdapter<viewScores> {
public ScoreAdapter(Context context, ArrayList<viewScores> scores) {
super(context, 0, scores);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
viewScores score1 = getItem(position);
if (convertView == null){
convertView = LayoutInflater.from(getContext()).inflate(R.layout.activity_main, parent, false);
}
TextView ListView1 = (TextView) convertView.findViewById(R.id.dispScores);
ListView1.setText(score1.hole);
return convertView;
}
}
The app doesn't crash and I am able to enter values into my EditText. Below is the XML for the ListView.
<ListView
android:id="#+id/dispScores"
android:layout_width="250dp"
android:layout_height="250dp"
android:layout_marginLeft="15dp"
android:layout_marginStart="15dp"
app:layout_constraintLeft_toLeftOf="parent"
tools:layout_constraintLeft_creator="1"
tools:layout_constraintTop_creator="1"
tools:layout_editor_absoluteY="244dp" />

Whenever you update the model observed by your adapter, you need to call
adapter.notifyDataSetChanged()
So in your case,
viewScores addScore = new viewScores(input1.getText().toString());
savedScores.add(addScore);
adapter.notifyDataSetChanged()

How to reload list view after delete all item?

I have a delete all button and everytime it delete all item in a listview, the listview won't road but stay the same, they will reload only when I create a new item or restart this activity. I have print a log on my code and it seems that the list view reload before the delete method called. my code is this:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DBHelper db = new DBHelper(this);
final ListView listView = (ListView) findViewById(R.id.listView);
TextView empty = (TextView) findViewById(R.id.empty);
ArrayList<Inventory> listArray = new ArrayList<>();
listArray.clear();
listArray = db.read();
if (listArray.size() == 0) {
empty.setText("No Items");
} else {
empty.setText("");
}
ListViewAdapter customAdapter = new ListViewAdapter(listArray);
customAdapter.notifyDataSetChanged();
listView.setAdapter(customAdapter);
Button add_button = (Button) findViewById(R.id.button);
add_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
addNewItem(view);
}
});
Button button_deleteAll = (Button) findViewById(R.id.button_deleteAll);
button_deleteAll.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
deteleAll();
DBHelper db = new DBHelper(MainActivity.this);
final ListView listView = (ListView) findViewById(R.id.listView);
TextView empty = (TextView) findViewById(R.id.empty);
ArrayList<Inventory> listArray = new ArrayList<>();
listArray.clear();
listArray = db.read();
Log.v("arraysize:", String.valueOf(listArray.size()));
if (listArray.size() == 0) {
empty.setText("No Items");
} else {
empty.setText("");
}
ListViewAdapter customAdapter = new ListViewAdapter(listArray);
customAdapter.notifyDataSetChanged();
listView.setAdapter(customAdapter);
}
});
}
The method deleteAll() deletes all the data in SQLite.
I wish to know how to reload listview after this method called, rather than reload before this method.

add the delete all method in your adapter. call the deleteAll method of your adapter whenever button was clicked. the deleteAll method would be like below:
public void setListArray(ArrayList arrayList)
{
//assuming your adapter list is named "listArray"
this.listArray = arrayList;
notifyDataSetChanged();
}
and in your button click simply write this code:
button_deleteAll.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//assuming your list of itames here is named "mListArray"
mListArray.clear();
adapter.setListArray(mListArray);
}
}

I guess there is no need to initialize the customAdapter again in the button OnClick method. Also no need to setAdapter again.
Try to remove these lines in the onClick method.
Hope this fixes you issue.

Just add notifyDataSetChanged(); to your Adapter, inside a Listener. For example:
myListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override public void onItemClick(AdapterView<?> parent, android.view.View view, int position, long id) {
myArrayList.remove(position);
myArrayAdapter.notifyDataSetChanged();
}
});

use if-statement to recognize arraylist data in android

i want to use condition " if " for my array list
here is my code in (activity 1) to send string in textview with button to static variable that is in (exchange activity) :
Button btn1 = (Button) findViewById(R.id.btn1);
final TextView text = (TextView) findViewById(R.id.txt1);
btn1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
exchange.in =text.getText().toString();
}
});
here is my static variable in (exchange activity)
public static String in;
and here is my (activity 2) code that i use array list in it to receive & store string from (activity 1) that is in static variable (exchange.in)
ListView list;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<String> web = new ArrayList<String>(10);
for (int i = 0; i < 10; i++) {
web.add("");
}
CustomList adapter = new
CustomList(activity_main.this, web);
list = (ListView) findViewById(R.id.list);
list.setAdapter(adapter);
}
now i don't know how to store data from (exchange.in) to arraylist and then use if condition to recognize that, if arraylist(0) was full, put data that is in (exchange.in) to arraylist(1) and it will continue like this...
is anyone know about this?

Listview not updating after arraylist is updated?

I've seen many other posts in this context, but none helped. Problem is when i click on the addField button, the listview inside dialog adds new view just once. But at other clicks it doesn't get updated though The adapter works correctly (I mean the getView is called and also the arrayList in the adapter is changed in size).
I've used notifyDataSetChanged() in the adapter class. No result! I used an instance of adpater class in activity and called myAdapter.notifyDataSetChanged(). No result!
here is my code:
public class MainActivity extends Activity {
ListView lvfid;
FieldAdapter fAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//some code
showFid();
}
private void showFiD(){
final ArrayList <HashMap<String,String>> al = new ArrayList<HashMap<String,String>>();
final Dialog dialog = new Dialog(MainActivity.this , R.style.DialogTheme);
dialog.setContentView(R.layout.field_dialog);
dialog.setCancelable(true);
dialog.show();
Button addField = (Button) dialog.findViewById(R.id.btnfidField);
lvfid = (ListView) dialog.findViewById(R.id.lvfid);
//Another plan i have tested, but no result:
//fAdapter = new FieldAdapter(dialog.getContext(),al);
//lvfid.setAdapter(fAdapter);
addField.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
HashMap<String,String> h = new HashMap<String,String>();
h.put("name", "");
h.put("value", "");
al.add(h);
lvfid.setAdapter(new FieldAdapter(dialog.getContext(), al));
//fAdapter.notifyDataSetChanged();
}
});
}
public class FieldAdapter extends BaseAdapter{
private ArrayList <HashMap <String,String>> arrayList;
private LayoutInflater inflater;
public FieldAdapter(Context context, ArrayList<HashMap <String,String>> arrayList) {
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
this.arrayList = arrayList;
}
#Override
public int getCount() {
return arrayList.size();
}
#Override
public Object getItem(int position) {
return position;
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup arg2) {
View view = null;
if (convertView == null)
view = inflater.inflate(R.layout.field_inflater, null);
else
view = convertView;
Holder holder = new Holder();
holder.edName = (EditText) view.findViewById(R.id.edfidName);
holder.edValue = (EditText) view.findViewById(R.id.edfidValue);
//holder.edName.setText(arrayList.get(position).get("name"));
//holder.edValue.setText(arrayList.get(position).get("value"));
return view;
}
private class Holder {
private EditText edName;
private EditText edValue;
}
}
}
UPDATE:
I'm sorry i took everybody's time. The stupid problem was that my listview was inside a scrollview where it must not be! I hope this helps others who have the same issue!

Use the notifyDataSetChanged() every time the list is updated.

I had the same problem. I was facing with this problem when I wanted to update the listView after onDateChanged(). I resolved it with an extra ArrayList variable and an extra custom adapter in your case FieldAdapter variable.
Update your listView with a refresh adapter and array list variables after any operations. For example after button clicks.
1. Define a counter.
2. Check when the button is clicked, increase counter by one
3. Every time check the counter, if counter is greater than 1 it means the button is clicked more than once so update the list view with new variables (arrayList, FeildAdapter)
I recommend you to define the variables as a private class fields and name them such as refreshedArrayList and refreshedAdapter

Option
Try to use the ArrayAdapter. And don't create a new adapter every
time you click on the button.
only call the add(T o) function from the ArrayAdapter.
Other Option:
add a add function to your FieldAdapter in the add field adapter add the object to your arraylist and call notifiyDataSetChanged(the adapter has aslo one and the adapter notifies all his observers)
also don't create a new adapter every time you click the button.

public class MainActivity extends Activity {
ListView lvfid;
FieldAdapter fAdapter;
ArrayList <HashMap<String,String>> al ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//some code
al = new ArrayList<HashMap<String,String>>();
lvfid.setAdapter(new FieldAdapter(MainActivity.this , al));
showFid();
}
private void showFiD(){
final Dialog dialog = new Dialog(MainActivity.this , R.style.DialogTheme);
dialog.setContentView(R.layout.field_dialog);
dialog.setCancelable(true);
dialog.show();
Button addField = (Button) dialog.findViewById(R.id.btnfidField);
lvfid = (ListView) dialog.findViewById(R.id.lvfid);
//Another plan i have tested, but no result:
//fAdapter = new FieldAdapter(dialog.getContext(),al);
//lvfid.setAdapter(fAdapter);
addField.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
HashMap<String,String> h = new HashMap<String,String>();
h.put("name", "");
h.put("value", "");
al.add(h);
fAdapter.notifyDataSetChanged();
}
});
}

I'm sorry i took everybody's time! The stupid problem was just my listview was inside a scrollview where it must not be! after getting the listview out of scrollview the problem got solved.

Updating Recycler Listview dynamically using Database

I saw all the questions which is similar to my question ( in this , this , this and this link )
I had myAdapter.notifyDataSetChanged() in my Activity but it doesn't work
I have 3 classes,
DBHelper - For storing and getting Database contents ( NO ISSUES HERE )
SimpleRecyclerAdapter - Adapter for RecyclerList
ThirdActivity
What i did in ThirdActivity :
I have TextBox to get data and store it in Database and a Button. In
the Onclicklistener of Button, i specified code to
get text from textbox
add it into table using DBHelper
retrive data as ArrayList from DBHelper
myAdapter.notifyDataSetChanged()
When i click the Button, I got Data in LogCat which i specified inside OnclickListener but it is not reflected to the listview.
Here is my code,
ThirdActivity:
public class ThirdActivity extends AppCompatActivity{
private DrawerLayout mDrawerLayout;
DbHelper dbHelper;
EditText et;
Button addButton;
RecyclerView rv;
ArrayList<String> myNotesList;
SimpleRecycler3Adapter adapter3;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.thirdactivity);
myNotesList = new ArrayList<>();
et=(EditText) findViewById(R.id.et);
addButton=(Button)findViewById(R.id.addButton);
rv = (RecyclerView) findViewById(R.id.dbListrv);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getBaseContext());
rv.setLayoutManager(linearLayoutManager);
rv.setHasFixedSize(true);
adapter3 = new SimpleRecycler3Adapter(myNotesList);
rv.setAdapter(adapter3);
dbHelper = new DbHelper(this, null, null, 1);
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d("DB", "Constructor");
String note=et.getText().toString();
dbHelper.addNote(note);
printData();
}
});
}
public void printData(){
Log.d("DB","Constructor");
myNotesList=dbHelper.databasetostring();
Log.d("DB","Data came"+myNotesList.get(myNotesList.size()-1));
// adapter3 = new SimpleRecycler3Adapter(myNotesList);
// rv.setAdapter(adapter3);
adapter3.notifyDataSetChanged();
}
}
SimpleRecyclerViewAdapter :
public class SimpleRecycler3Adapter extends RecyclerView.Adapter<SimpleRecycler3Adapter.NotesHolder> {
private ArrayList<String> myNotesList=new ArrayList<String>();
String TAG="ThirdAdapter kbt";
RecyclerView rv;
public SimpleRecycler3Adapter(ArrayList<String> myList) {
Log.d(TAG,"Constructor");
Log.d(TAG,"Not null");
int i = 0;
while (i < myNotesList.size()) {
myNotesList.add(myList.get(i).toString());
}
Log.d(TAG,"finish");
}
#Override
public NotesHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
Log.d(TAG,"On create started");
View view2 = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recyclerlist3_item, viewGroup, false);
Log.d(TAG,"ADAP STAR ONCR second switch 2nd line");
NotesHolder viewHolder2 = new NotesHolder(view2);
Log.d(TAG,"ADAP STAR ONCR second switch 3nd line");
return viewHolder2;
}
#Override
public void onBindViewHolder(NotesHolder notesHolder, int i) {
Log.d(TAG, "ONBIND SECOND i value is " + i);
// notesHolder.thumbnail.setImageResource(R.drawable.placeholder);
notesHolder.dblistitem.setText(myNotesList.get(i));
Log.d(TAG,"ONBIND second title issssss");
}
#Override
public int getItemCount() {
return myNotesList.size();
}
class NotesHolder extends RecyclerView.ViewHolder {
protected ImageView thumbnail;
protected TextView dblistitem;
public NotesHolder(View itemView) {
super(itemView);
Log.d(TAG, "JSON Inside HOLDER");
rv=(RecyclerView)itemView.findViewById(R.id.dbListrv);
// thumbnail = (ImageView) itemView.findViewById(R.id.thumbnail);
dblistitem = (TextView) itemView.findViewById(R.id.dblistitem);
}
}
}

You're not updating the myNotesList that is in adapter class but in activity class. But the adapter uses it's local myNotesList.
So on button click, update myNotesList of adapter with latest data available and notify the adapter.
EDIT
Pass the latest data to adapter. Have this method in adapter class and call this before notifyDataSetChanged();
public void updateNotes(ArrayList<String> notesList) {
myNotesList = notesList;
}

1.you are intializing your dbhelper after setting adapter to listview so it couldn't contain any data initially
2.for updating recycler view data list do as follows
myNotesList.clear();
myNotesList.addAll(dbHelper.databasetostring());
adapter3.notifyDataSetChanged();

You have a problem in your SimpleRecyclerViewAdapter, just change this:
while (i < myNotesList.size()) {
myNotesList.add(myList.get(i).toString());
}
For this:
myNotesList = myList;
And in your activity's printData() change:
myNotesList=dbHelper.databasetostring();
for this:
myNotesList.clear();
myNotesList.addAll(dbHelper.databasetostring());
adapter3.notifyDataSetChanged();
Explanation:
First you initialize myNotesList variable:
myNotesList = new ArrayList<>();
Then you initialize adapter3
adapter3 = new SimpleRecycler3Adapter(myNotesList);
But your adapter is not saving the reference, instead you're copying its data into another variable:
while (i < myNotesList.size()) {
myNotesList.add(myList.get(i).toString());
}
Doing that, if you change myNotesList variable in your activity will not modify your adapter's dataset.
In your method printData() you change myNotesList variable. Which will not touch your adapter or its data
public void printData(){
Log.d("DB","Constructor");
myNotesList=dbHelper.databasetostring();
Log.d("DB","Data came"+myNotesList.get(myNotesList.size()-1));
// adapter3 = new SimpleRecycler3Adapter(myNotesList);
// rv.setAdapter(adapter3);
adapter3.notifyDataSetChanged();
}

You can't change myNotesList by changing myList.
public SimpleRecycler3Adapter(ArrayList<String> myList) {
Log.d(TAG,"Constructor");
Log.d(TAG,"Not null");
// int i = 0;
// while (i < myNotesList.size()) {
// myNotesList.add(myList.get(i).toString());
// }
this.myNotesList = myList;
Log.d(TAG,"finish");
}

Not a good idea to call notifyDataSetChanged() when you know exactly what changed in your data collection.
See this implementation here.
They have even documented to use notifyDataSetChanged() as a last resort in this doc.
You get nice animations for free if you use methods like notifyItemInserted() and the rest.
Also do not go on replacing the collection object entirely, see the implmentation link that has been attached.