Develop Reference

How to disable a single row and change its background color in a listview, without a button (or a method if possible)?

The title of this post says it all.
This code works without any problems:
package abc.AvailableCars;
import android.graphics.Color;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class carListActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.car_list_layout);
final ListView carListview = (ListView) findViewById(R.id.list_view);
final Button dButton = (Button) findViewById(R.id.disable_button);
String[] cars = {"Maxima GXE", "Passat", "Focus SE", "Mazda6", "Avalon", :Sentra GXE"};
final List<String> list_of_cars = new ArrayList<String>(Arrays.asList(cars));
final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>
(this, android.R.layout.simple_list_item_1, list_of_cars);
carListview.setAdapter(arrayAdapter);
dButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
int chosenRow = 3;
carListview.getChildAt(3).setEnabled(false);
carListview.getChildAt(3).setBackgroundColor(Color.parseColor("#3f51b5"));
}
});
}
}
This is in my listview .xml file:
<Button
android:id="#+id/disable_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Disable A Row"
/>
But, when I comment-out everything that belongs to the button, like below, and the Car List class is called, the app crashes with the error in the Logcat:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setEnabled(boolean)' on a null object reference:
final ListView carListview = (ListView) findViewById(R.id.list_view);
//final Button dButton = (Button) findViewById(R.id.disable_button);
String[] cars = {"Maxima GXE", "Passat", "Focus SE", "Mazda6", "Avalon"};
final List<String> list_of_cars = new ArrayList<String>(Arrays.asList(cars));
final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>
(this, android.R.layout.simple_list_item_1, list_of_cars);
carListview.setAdapter(arrayAdapter);
//dButton.setOnClickListener(new View.OnClickListener() {
//#Override
//public void onClick(View v) {
int chosenRow = 3;
carListview.getChildAt(chosenRow).setEnabled(false);
carListview.getChildAt(chosenRow).setBackgroundColor(Color.parseColor("#3f51b5"));
}
//});
}
//}
I'm not an Android newbie anymore, but this is eluding me.
I want the chosen row to be disabled and the color set as soon as the listview is shown.
How can I do this programmatically without a button?
I have tried every variation I can think of, getView(), even a fake click.
Just in case it makes a difference, this code is in a separate class and file than the MainActivity.java file, and is called in that file.
There has to be a simple answer. What do I need to change?
Please be verbose.
Thank you.

You are calling carListview.getChildAt(chosenRow) when you set up your list view, in onCreate. Your list view is not ready yet. Try moving this code to your onResume - should look something like this:
#Override
public void onResume(){
super.onResume();
arrayAdapter.notifyDataSetChanged();
int chosenRow = 3;
carListview.getChildAt(chosenRow).setEnabled(false);
carListview.getChildAt(chosenRow).setBackgroundColor(Color.parseColor("#3f51b5"));
}
This is a pretty simple case - your chosenRow number is generated by you. You might need a custom Adapter if you need it to be algorithmic or user-driven. Have a look at this tutorial.

From my understanding, since listViews are views, they have to be Overridden for some things to be changed in them.
I chose not to disable the required rows, but check for them in code.
The complete code that works is below.
Some credit goes to Raghunandan for his/her answer at-
Android - Change background color of specific item of ListView
Again, sorry, but the indentation of the code wouldn't work correctly for some reason.
import android.graphics.Color;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class CarListActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.car_list_layout);
final ListView carListview = (ListView) findViewById(R.id.list_view);
String[] cars = {"European Cars:", "Mercedes", "Passat", "Bently", "Porsche", "BMW", "Yugo","Land Rover",
"Japanese Cars:", "Maxima GXE", "Mazda6", "Avalon", "Toyota", "Honda", ""};
final List<String> list_of_cars = new ArrayList<String>(Arrays.asList(cars));
final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>
(this, android.R.layout.simple_list_item_1, list_of_cars);
//------------------------------------------
carListview.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list_of_cars) {
// Since listViews are views, they have to be Overrdden for some things to be changed in them.
#Override
public View getView(int rowPosition, View convertView, ViewGroup parent) {
View row = super.getView(rowPosition, convertView, parent);
//------------------------------------------
// This works. I have only tried this for two rows, the two I wanted. I expected this line to crash the app, but it didn't.
if(getItem(rowPosition).equals("European Cars:") || getItem(rowPosition).equals("Japanese Cars:")) {
// Make the two rows have a white background color.
row.setBackgroundColor(Color.WHITE); // this command WORKS fine by itself.
// row.setEnabled(false); this command caused "bleeding" over into other rows, so I will check for the rows in a condition.
} // both of the getItems end here.
else {
// All of the other rows should have this color.
row.setBackgroundColor(Color.parseColor("#EEE8AA"));
// the default color
} // else ends here.
//------------------------------------------
return row;
//------------------------------------------
} // getView ends here.
}); // carListview.setAdapter ends here.
} // onCreate ends here.
} // CarListActivity ends here.
Thanks, and I hope this helps others.

Android changing activity issues, crashes on selection

So, what I'm trying to do is have a main menu and then press a button, it loads a list of countries.
now I've seemed to have set it up right, no errors I can see, but the app crashes before I load this activity (the lists) the main menu is fine, and I added another button with a blank activity which loads just fine.
logCat is giving me these errors
E/ArrayAdapter: You must supply a resource ID for a TextView
D/AndroidRuntime: Shutting down VM
java.lang.IllegalStateException: ArrayAdapter requires the resource ID to be a TextView
and I'm not sure what it's asking for beyond the textView
heres my XML:
<ListView
android:id="#+id/text1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:divider="#f897"
android:dividerHeight="1dp"
android:listSelector="#0f0"/>
and my Java:
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class countries extends AppCompatActivity {
ListView simpleList;
String countryList[] = {"India", "China", "Australia", "Portugal", "USA","England", "NewZealand", "Germany", "France","South Africa"};
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_countries);
simpleList = (ListView)findViewById(R.id.text1);
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, R.layout.activity_countries, countryList);
simpleList.setAdapter(arrayAdapter);
}
}
any help?

change:
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, R.layout.activity_countries, countryList);
to:
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,countryList);
your code not work because you use default ArrayAdapter with custom item layout

You array adapter expects the layout to be a TextView, but it look like R.layout.activity_countries is an activity layout?

You should create a custom adapter and custom view for each listview's row. Check it here: Custom Adapter for List View

listView adapter force close

I don't know why but I am getting an error while setting the adapter.
ERROR:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a
null object reference
Even after referencing properly it is throwing the null exception.
Can anyone tell me where I am going wrong.
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView lView = (ListView) findViewById(R.id.lView);
ArrayList<String> item = new ArrayList<>();
for( int i = 0 ; i < 10 ; i++ ){
item.add("Item"+i);
}
ArrayAdapter<String> madapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,item);
lView.setAdapter(madapter);
}
}

This mostly happens in cases where layout does not contains the view you are refering by the specified id, check & change activity_main and change the Listview id to lView

This issue is due to Android system unable to find the lView in the activity_main.xml which is used for the MainActivity.
Please check in other activity_main.xml files layout, large-layout, xlarge-layout folders and add that ListView in that files if it is not there.
The layout will be picked by the android system based on the device, Then the UI components which are used in the code should be present in that layout.

on layout of activity_main has no View id.
OR
replice field android.R.layout.simple_list_item_1 with other items in line ArrayAdapter<String> madapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,item);

Dynamically add items in list view

I want to make a dynamic list view which gets the user credentials when I login for the first time and displays it in a list the next time I start the app. I know how to send the username from one intent to another. i haven't focused on the SQLite part yet, will do that later. I'm facing problems in creating the dynamic list view.
Found one very useful thread - Dynamically add elements to a listView Android
he used a button on the screen and called the method onClick to populate the list. Can i do it without the button? I want it to automatically happen once i am able to login.
how can i use the statements in my code?
listItems.add(value);
adapter.notifyDataSetChanged();
here value is the username i am getting from some other intent.
please help. thanks!

For this Just use the example given below:
For Instance you are Adding Some Strings into your List
So Create a ListArray like this
ArrayList<String> listItems = new ArrayList<String>();
now whenever you want to add certain string into list just do this thing
EditText editText = (EditText) findViewById(R.id.edit);
listItems.add("my string"); OR
listItems.add(editText.getText.toString()); //incase if you are getting string value from editText and adding it into the list
Use this Xml inside your linear layout in main.xml
<EditText android:id="#+id/edit"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
Now when you have added one item dynamically then call this
adapter.notifyDataSetChanged();
The above will update your list and display the upadted list.
For more info about this see the following links:
http://www.androidpeople.com/android-custom-listview-tutorial-part-1
http://www.androidpeople.com/android-custom-listview-tutorial-part-2
http://www.androidpeople.com/android-custom-dynamic-listview-%E2%80%93part3
In these tutorials you can replace String[] with ArrayList as given at the top of the answer ook and when you want to add any item just simply use the second code snippet.
Thanks
sHaH

The best way to do this will be to use ArrayAdapter. When modifying the adapter it automatically refresh itself so you don't have to call notifyDataSetChanged.

You can try out this code to add elements dynamically to list view.
You can do it with out button click also.
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
public class MainActivity extends Activity {
//step2 : create all the variables.
EditText et;
Button b;
ListView lv;
ArrayList<string> al;
ArrayAdapter<string> aa;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//step3 : intitalize all the variables.
et = (EditText) findViewById(R.id.editText1);
b = (Button) findViewById(R.id.button1);
lv = (ListView) findViewById(R.id.listView1);
al = new ArrayList<string>();//initialize array list
aa = new ArrayAdapter<string>(this,
android.R.layout.simple_list_item_1,
al);//step4 : establish communication bw arraylist and adapter
//step5 : establish communication bw adapter and dest (listview)
lv.setAdapter(aa);
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView parent,
View v, int arg2,
long arg3) {
String item = al.get(arg2);
Toast.makeText(getApplicationContext(), item, 0).show();
}
});
//step6 : button click logic
b.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//step i: take text from et and add to arraylist
String item = et.getText().toString();
al.add(0, item);
//step ii: notify to adapter
aa.notifyDataSetChanged();
//step iii: clr edit text
et.setText("");
}
});
}
}
For complete code check this list view example

Adapter for list view

please guide me with this program. Why do we need to use an array adapter to show the list? What is this "adapter", and can we display things directly in the ListView, without an adapter? Like, can we set setListAdapter(names) instead of setListAdapter(adapter);? Thanks.
Here is the code:
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
public class Episode7 extends ListActivity {
String[] names = {
"Elliot","Geoffrey","Samuel","Harvey","Ian","Nina","Jessica",
"John","Kathleen","Keith","Laura","Lloyd"
};
/** Called when the activity is first created. */
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Create an ArrayAdapter that will contain all list items
ArrayAdapter<String> adapter;
/* Assign the name array to that adapter and
also choose a simple layout for the list items */
adapter = new ArrayAdapter<String>(
this,
android.R.layout.simple_list_item_1,
names);
// Assign the adapter to this ListActivity
setListAdapter(adapter);
}
}

From the android API reference,
An Adapter object acts as a bridge between an AdapterView and the underlying data for that view. The Adapter provides access to the data items. The Adapter is also responsible for making a View for each item in the data set.
It basically a set of interfaces that determine how the data will be handled by the list. You can use different pre-made adapter classes in your lists or create your own if you want to present custom data.
Take a look at this page in the Dev Guide: http://developer.android.com/guide/topics/ui/binding.html
Lars Vogel has a nice tutorial also: http://www.vogella.de/articles/AndroidListView/article.html

The Adapter acts as both a container for the information you want to display, and allows you to change how it is displayed by over-riding the getView() method of the adapter. Normally, by default, the adapter will call the toString() method of the Object used to create the Adapter and set the text in the TextView that is referenced in the layout provided by android.R.layout.simple_list_item_1... but by over-riding the adapter's getView(), you can have a more complicated layout display for the list.
To answer the initial question... you must use an adapter with a ListView.

This is how I do it and it works for me:
import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class ListViewDemo extends Activity {
// --------- Create your string array, adapter and ListView
String[] items = {"Cars", "Money","Vacation","Electronics",
"Shoes","Jewelry", "Buku bucks","Cash","Ham","Swag","Straight Cash","Homies","Roll Dawgs","Nate Dogg","Wiz Khalifa","Mac Miller","Chitty Bang",
"Sam Adams","Technine","Kanye West","Rims","Escalade","Spreewells","Chrome Rims","24's",
"Lebron James","Dwayne Wade","Andre Iguodala","Allen Iverson","Jodi Meeks",
"Levoy Allen","Mo Williams","Eric Snow","Alien Iverson","Laptop","Phone","Tablet"};
ArrayAdapter<String> adapter;
ListView cashList;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
cashList = new ListView(this);
// create the array adapter<String>(context, layout, array)
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);
// add the adapter to the list
cashList.setAdapter(adapter);
// set the list as the content view
setContentView(cashList);
}
}