I am creating a playlist with 2 lines of name and genre, how to I can delete it.
This is MainActivity :
String[] gene, sl;
...
adp = new Adapter(MainActivity.this, gene, sl);
lv.setAdapter(adp);
This is Adapter
public class Adapter extends ArrayAdapter<String> {
private final Activity context;
private final String[] gene;
private final String[] sl;
SharedPreferences preferences;
public Adapter(Activity context, String[] gene ,String[] sl) {
super(context, R.layout.activity_m , gene);
this.context = context;
this.gene = gene;
this.sl = sl;
}
private class ViewHolder{
TextView txtgene, txtsl;
}
#Override
public View getView(final int position, View view, ViewGroup parent) {
ViewHolder holder;
if (view == null) {
LayoutInflater inflater = context.getLayoutInflater();
view = inflater.inflate(R.layout.activity_m, null, true);
holder = new ViewHolder();
holder.txtgene = (TextView) view.findViewById(R.id.txtgene);
holder.txtsl = (TextView) view.findViewById(R.id.txtsl);
view.setTag(holder);
}else{
holder = (ViewHolder) view.getTag();
}
if (gene[position] != null) {
holder.txtgene.setText(gene[position]);
}
holder.txtsl.setText(sl[position]);
return view;
}
}
How to remove an item when you know its exact position ?
Thank !
You are using the ArrayAdapter constructor that takes an array. This in turn will create an immutable List internal to the ArrayAdapter. So, you will not be able to modify your adapter going this route.
Instead, make a new ArrayList from your array and call the ArrayAdapter constructor that takes a List.
So, change the super call in your Adapter constructor to this:
super(context, R.layout.activity_m, new ArrayList<>(Arrays.asList(gene)));
And then, when you want to remove an item given it's position, do this:
adp.remove(getItem(position));
PS: You should consider refactoring your gene and sl arrays into a class and then use it as the type of your List.
I am trying to create my first Custom Adapter to generate a listview for my android app. I am getting my data from an Api call and then process it and store it in an arraylist:-
class Person{
String bioguide;
String image;
String lastname;
String firstname;
String district;
String state;
String party;}
public static ArrayList<Person> personData = new ArrayList<Person>();
Now in the onpostexecute section I am trying to create a listview and custom adapter to display my data as follows:-
ListView yourListView = (ListView) rootView.findViewById(R.id.state_listView);
ListAdapter customAdapter = new ArrayAdapter<Person>(ByState.this, R.layout.bystate_itemview,personData);
yourListView .setAdapter(customAdapter);
}
}
public class ListAdapter extends ArrayAdapter<Person> {
public ListAdapter(Context context, int textViewResourceId) {
super(context, textViewResourceId);
}
public ListAdapter(Context context, int resource, ArrayList<Person> items) {
super(context, resource, items);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi;
vi = LayoutInflater.from(getContext());
v = vi.inflate(R.layout.bystate_itemview, null);
}
Person p = getItem(position);
if (p != null) {
TextView tt1 = (TextView) v.findViewById(R.id.last_name);
TextView tt2 = (TextView) v.findViewById(R.id.first_name);
if (tt1 != null) {
tt1.setText(p.getLastname());
}
if (tt2 != null) {
tt2.setText(p.getFirstname());
}
}
return v;
}
}
}
I got the above code following some internet tutorial. The thing is I am getting an error in the line where I use the customadapter first to invoke the constructor of custom adapter. It says cannot resolve constructor. Can someone help me in understanding this. I know I have not defined the proper constructor for my case please let me know the changes. I am creating the listview inside a fragment and the fragment class name is ByState.
In second line replace
ListAdapter customAdapter = new ArrayAdapter<Person>(ByState.this, R.layout.bystate_itemview,personData);
by
ListAdapter customAdapter = new ListAdapter(ByState.this, R.layout.bystate_itemview, personData);
You create your own adapter class, but invoke standart ArrayAdapter
How do I program my adapter in order to visualize the contents of an ArrayList in a onPostExecute inside an AsynkTask?
I have got the following class:
class PlatoCuenta{
public String id;
public String name;
public Integer served_as;
public String served;
public String price;
public String quantity;
public String title_cuenta;
}
I have got the following array list:
ArrayList<PlatoCuenta> bebidas=new ArrayList<PlatoCuenta>();
bebidas=new ArrayList<PlatoCuenta>();
JSONArray mArray = new JSONArray(jsonstr);
for(int i = 0; i < mArray.length(); ++i) {
JSONObject currentObject = mArray.getJSONObject(i);
PlatoCuenta producto= new PlatoCuenta();
SectionItem SectionCuenta = new SectionItem();
producto.id=currentObject.getString("id");
producto.served=currentObject.getString("served");
if(currentObject.getString("price").equals("None"))
producto.price="0.00";
else
producto.price=currentObject.getString("price");
producto.name= currentObject.getString("product_name");
producto.quantity=currentObject.getString("product_number");
producto.served_as = currentObject.getInt("serv_order");
if(producto.served_as==0){
SectionCuenta.title="bebidas";
producto.title_cuenta=SectionCuenta.title;
bebidas.add(producto);
}
if(producto.served_as==2){
SectionCuenta.title="entrantes";
producto.title_cuenta=SectionCuenta.title;
bebidas.add(producto);
}
}
Assume that you have ArrayList<PlatoCuenta> bebidas=new ArrayList<PlatoCuenta>();. The general steps for visualize a listview are:
Create a row layout row.xml
Create an adapter for the row
Set adapter to the listview.
Again, suppose that you already have the design of your row.xml. To create an adapter (step 2).
public class MyAdapter extends BaseAdapter {
public MySimpleArrayAdapter(Context context, ArrayList list) {
super(context, R.layout.rowlayout, values);
//....
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.row.xml, parent, false);
//continue creating your row here
return rowView;
}
}
And in onPostExecute:
MyAdapter adapter = new MyAdapter(context,bebidas);
listView.setAdapter(adapter);
Good tutorial: Custom ListView
I'm trying to create a spinner with default empty selected item, but it displays the first item from the choices of spinner. If I add null value to my string, which is the source of choices in spinner, then after opening spinner that empty row is displayed. How should I do it? Here's code I'm using:
String[] ch = {"Session1", "Session2", "Session3"};
Spinner sp = (Spinner)findViewById(R.id.spinner1);
TextView sess_name = findViewById(R.id.sessname);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,ch);
sp.setAdapter(adapter);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener({
#Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
int index = arg0.getSelectedItemPosition();
sess_name.setText(ch[index]);
Toast.makeText(getBaseContext(), "You have selected item : " + ch[index], Toast.LENGTH_SHORT).show();
}
Barak's solution have a problem. When you select the first item, Spinner won't call OnItemSelectedListener's onItemSelected() and refresh the empty content because the previous position and selection position both is 0.
First put a empty string at the begin of your string array:
String[] test = {" ", "one", "two", "three"};
Second build adapter, don't modify getView(), modify getDropDownView(). Set the empty View's height to 1px.
public class MyArrayAdapter extends ArrayAdapter<String> {
private static final int ITEM_HEIGHT = ViewGroup.LayoutParams.WRAP_CONTENT;
private int textViewResourceId;
public MyArrayAdapter(Context context,
int textViewResourceId,
String[] objects) {
super(context, textViewResourceId, objects);
this.textViewResourceId = textViewResourceId;
}
#Override
public View getDropDownView(int position, View convertView, #NonNull ViewGroup parent) {
TextView textView;
if (convertView == null) {
textView = (TextView) LayoutInflater.from(getContext())
.inflate(textViewResourceId, parent, false);
} else {
textView = (TextView) convertView;
}
textView.setText(getItem(position));
if (position == 0) {
ViewGroup.LayoutParams layoutParams = textView.getLayoutParams();
layoutParams.height = 1;
textView.setLayoutParams(layoutParams);
} else {
ViewGroup.LayoutParams layoutParams = textView.getLayoutParams();
layoutParams.height = ITEM_HEIGHT;
textView.setLayoutParams(layoutParams);
}
return textView;
}
}
I'm a little late to the party, but here is what I did to solve this.
If the user cancels out of selecting an initial item the spinner will retain the initial empty state. Once an initial item has been selected it works as 'normal'
Works on 2.3.3+, I have not tested on 2.2 and below
First, create an adapter class...
public class EmptyFirstItemAdapter extends ArrayAdapter<String>{
//Track the removal of the empty item
private boolean emptyRemoved = false;
/** Adjust the constructor(s) to fit your purposes. */
public EmptyFirstitemAdapter(Context context, List<String> objects) {
super(context, android.R.layout.simple_spinner_item, objects);
setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
}
#Override
public int getCount() {
//Adjust the count based on the removal of the empty item
if(emptyRemoved){
return super.getCount();
}
return super.getCount()-1;
}
#Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
if(!emptyRemoved){
// Remove the empty item the first time the dropdown is displayed.
emptyRemoved = true;
// Set to false to prevent auto-selecting the first item after removal.
setNotifyOnChange(false);
remove(getItem(0));
// Set it back to true for future changes.
setNotifyOnChange(true);
}
return super.getDropDownView(position, convertView, parent);
}
#Override
public long getItemId(int position) {
// Adjust the id after removal to keep the id's the same as pre-removal.
if(emptyRemoved){
return position +1;
}
return position;
}
}
Here is the string array I used in strings.xml
<string-array name="my_items">
<item></item>
<item>Item 1</item>
<item>Item 2</item>
</string-array>
Next, add an OnItemSelectedListener to your Spinner...
mSpinner = (Spinner) mRootView.findViewById(R.id.spinner);
String[] opts = getResources().getStringArray(R.array.my_items);
//DO NOT set the entries in XML OR use an array directly, the adapter will get an immutable List.
List<String> vals = new ArrayList<String>(Arrays.asList(opts));
final EmptyFirstitemAdapter adapter = new EmptyFirstitemAdapter(getActivity(), vals);
mSpinner.setAdapter(adapter);
mSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
//Track that we have updated after removing the empty item
private boolean mInitialized = false;
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
if(!mInitialized && position == 0 && id == 1){
// User selected the 1st item after the 'empty' item was initially removed,
// update the data set to compensate for the removed item.
mInitialized = true;
adapter.notifyDataSetChanged();
}
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
// Nothing to do
}
});
It may not be a 'perfect' solution, but I hope it helps someone.
After some thinking, I believe I've come up with a method to achieve your goal. It involves creating a
custom adapter and setting/maintaining a flag to determine if an item from the spinner has been selected.
Using this method you do not need to create/use false data (your empty string).
Basically, the adapters getView method sets the text for the closed spinner. So if you override that
and set a conditional in there, you can have a blank field on startup and after you make a selection have
it appear in the closed spinner box. The only thing is you need to remember to set the flag whenever you
need to see the value in the closed spinner.
I've created a small example program (code below).
Note that I only added the single constructor I needed for my example. You can implement all the standard
ArrayAdapter constructors or only the one(s) you need.
SpinnerTest.java
public class SpinnerTestActivity extends Activity {
private String[] planets = { "Mercury", "Venus", "Earth", "Mars",
"Jupiter", "Saturn", "Uranus", "Neptune" };
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Spinner spinner = (Spinner) findViewById(R.id.spinner);
CustomAdapter adapter = new CustomAdapter(this, // Use our custom adapter
android.R.layout.simple_spinner_item, planets);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
#Override
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
CustomAdapter.flag = true; // Set adapter flag that something
has been chosen
}
});
}
}
CustomAdapter.java
public class CustomAdapter extends ArrayAdapter {
private Context context;
private int textViewResourceId;
private String[] objects;
public static boolean flag = false;
public CustomAdapter(Context context, int textViewResourceId,
String[] objects) {
super(context, textViewResourceId, objects);
this.context = context;
this.textViewResourceId = textViewResourceId;
this.objects = objects;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null)
convertView = View.inflate(context, textViewResourceId, null);
if (flag != false) {
TextView tv = (TextView) convertView;
tv.setText(objects[position]);
}
return convertView;
}
}
Here is what I use. It properly handles null (empty) selection in a generic manner. It works with any model class T, as long as class T properly implements toString(), to display the text shown in the spinner, and equals(), so that items may be selected by reference rather than by positional index.
package com.10xdev.android.components;
import android.content.Context;
import android.graphics.Color;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
/**
* A spinner where no selection is possible, and other enhancements.
* requires model class to properly implement Object.equals, with semantic comparaison (such as id comparaison)
* and a proper toString(), whose result will be displayed in the spinner
*
* #author tony.benbrahim
*/
public class EnhancedSpinner<T> extends Spinner {
private final EnhanceArraySpinnerAdapter<T> spinnerAdapter;
private final List<T> items = new ArrayList<>();
private T selected = null;
public EnhancedSpinner(final Context context, final AttributeSet attributeSet) {
super(context, attributeSet);
spinnerAdapter = new EnhanceArraySpinnerAdapter<>(context, items);
setAdapter(spinnerAdapter);
}
/**
* sets the items to be displayed
*
* #param items
*/
public void setItems(final List<T> items) {
this.items.clear();
//very iffy, but works because of type erasure
this.items.add((T) "");
this.items.addAll(items);
spinnerAdapter.notifyDataSetChanged();
updateSelected();
}
/**
* set the selected item. this may be called before or after setting items
*
* #param item the item to select, or null to clear the selection
*/
public void setSelected(final T item) {
this.selected = item;
updateSelected();
}
/**
* gets the selected item, or null if no item is selected
*
* #return
*/
#Override
public T getSelectedItem() {
return getSelectedItemPosition() != 0 ? (T) super.getSelectedItem() : null;
}
/**
* set the error message for the select
*
* #param errorMessage
*/
public void setError(final String errorMessage) {
final TextView errorText = (TextView) getSelectedView();
errorText.setError("error");
errorText.setTextColor(Color.RED);
errorText.setText(errorMessage);
}
private void updateSelected() {
if (selected == null) {
setSelection(0);
} else {
for (int i = 1; i < items.size(); ++i) {
if (selected.equals(items.get(i))) {
setSelection(i);
break;
}
}
}
}
private class EnhanceArraySpinnerAdapter<T> extends ArrayAdapter<T> {
private final LayoutInflater inflater;
public EnhanceArraySpinnerAdapter(final Context context, final List<T> objects) {
super(context, android.R.layout.simple_spinner_item, objects);
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
#Override
public View getDropDownView(final int position, final View convertView, final ViewGroup parent) {
final TextView textView = convertView != null ? (TextView) convertView
: (TextView) inflater.inflate(android.R.layout.simple_spinner_item, parent, false);
final Object item = getItem(position);
textView.setText(item.toString());
final ViewGroup.LayoutParams layoutParams = textView.getLayoutParams();
layoutParams.height = position == 0 ? 1 : LayoutParams.WRAP_CONTENT;
textView.setLayoutParams(layoutParams);
return textView;
}
}
}
You have to put the first element of the spinner empty, or with an string indicating that nothing is selected like the following:
String[] ch= {"","Session1", "Session2", "Session3"};
or
String[] ch= {"Nothing selected", "Session1", "Session2", "Session3"};
hope to help
Is there a working example out there that demonstrates how to append additional rows in ListView dynamically?
For example:
you are pulling RSS feeds from
different domains
you then display the first 10 items
in the ListView (while you have
other threads running in the
background continue pulling feeds)
you scroll and reach the bottom of
the List and click at a button to
view more items
the ListView will then get appended
with additional 10 items, which
makes 20 items now in total.
Any advice how to accomplish this?
Nicholas
To add new item to your list dynamically you have to get adapter class from your ListActivity and simply add new elements. When you add items directly to adapter, notifyDataSetChanged is called automatically for you - and the view updates itself. You can also provide your own adapter (extending ArrayAdapter) and override the constructor taking List parameter. You can use this list just as you use adapter, but in this case you have to call adapter.notifyDataSetChanged() by yourself - to refresh the view.
Please, take a look at the example below:
public class CustomList extends ListActivity {
private LayoutInflater mInflater;
private Vector<RowData> data;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mInflater = (LayoutInflater) getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
data = new Vector<RowData>();
RowData rd = new RowData("item1", "description1");
data.add(rd);
rd = new RowData("item2", "description2");
data.add(rd);
rd = new RowData("item2", "description3");
data.add(rd);
CustomAdapter adapter = new CustomAdapter(this, R.layout.custom_row,R.id.item, data);
setListAdapter(adapter);
getListView().setTextFilterEnabled(true);
}
public void onListItemClick(ListView parent, View v, int position, long id) {
CustomAdapter adapter = (CustomAdapter) parent.getAdapter();
RowData row = adapter.getItem(position);
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle(row.mItem);
builder.setMessage(row.mDescription + " -> " + position );
builder.setPositiveButton("ok", null);
builder.show();
}
/**
* Data type used for custom adapter. Single item of the adapter.
*/
private class RowData {
protected String mItem;
protected String mDescription;
RowData(String item, String description){
mItem = item;
mDescription = description;
}
#Override
public String toString() {
return mItem + " " + mDescription;
}
}
private class CustomAdapter extends ArrayAdapter<RowData> {
public CustomAdapter(Context context, int resource,
int textViewResourceId, List<RowData> objects) {
super(context, resource, textViewResourceId, objects);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
//widgets displayed by each item in your list
TextView item = null;
TextView description = null;
//data from your adapter
RowData rowData= getItem(position);
//we want to reuse already constructed row views...
if(null == convertView){
convertView = mInflater.inflate(R.layout.custom_row, null);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
}
//
holder = (ViewHolder) convertView.getTag();
item = holder.getItem();
item.setText(rowData.mItem);
description = holder.getDescription();
description.setText(rowData.mDescription);
return convertView;
}
}
/**
* Wrapper for row data.
*
*/
private class ViewHolder {
private View mRow;
private TextView description = null;
private TextView item = null;
public ViewHolder(View row) {
mRow = row;
}
public TextView getDescription() {
if(null == description){
description = (TextView) mRow.findViewById(R.id.description);
}
return description;
}
public TextView getItem() {
if(null == item){
item = (TextView) mRow.findViewById(R.id.item);
}
return item;
}
}
}
You can extend the example above and add "more" button - which just add new items to your adapter (or vector). Regards!