Develop Reference

The dropdown view of AutoCompleteTextView displays with an error width

I follow the official instruction of autocompletetextview to create a new one in my project. I think that is easy, but when I run the code, I find the outcome is far from my expectation.
As you can see on the picture, when I type "f" in the textview, the dropdown view which is supposed to display "Franch", only displayed "Fr..", though I have add "setDropDownWidth(100)" to the textview.
I really want to know what happen and how to solve it.
And below is my code:
xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<AutoCompleteTextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/countries_list"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity:
package com.example.autocompletetextview;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
public class MainActivity extends AppCompatActivity {
private static final String[] COUNTRIES = new String[] {
"Belgium", "France", "Italy", "Germany", "Spain"
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_dropdown_item_1line, COUNTRIES);
AutoCompleteTextView textView = (AutoCompleteTextView)
findViewById(R.id.countries_list);
textView.setThreshold(1);
textView.setDropDownWidth(100);
textView.setAdapter(adapter);
}
}

This occurred because of this textView.setDropDownWidth(100). It too small so the text will be wrap.
My solution is just remove it, so the autocomplete will wrap your edittext width, or setDropDownWidth with a bigger value.

what is the difference between notifyDataSetChanged and add(T object) or addAll(T... items) methods in array adapter?

I'm trying to learn List view and adapters, made a very basic app to learn in which I have a button that inserts a String object to the data source of an array adapter and the other view is list view which shows this data set. add() and addAll() method apends the data to the data set but when I do that list view shows it but I didn't call notifyDataSetChanged method, so why list view refreshed itself and if it did so then why do I need the method? Could anyone help me by giving some clarity? add(), addAll() and insert() methods already making the list view show the new added data but how? so what's the difference?
the app's only layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical"
android:padding="8dp">
<Button
android:id="#+id/insert_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:text="insert data"/>
<ListView
android:id="#+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
the main activity code:
package famiddle.smart.apps.learningandroid;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import androidx.appcompat.app.AppCompatActivity;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
Button insertButton;
ArrayAdapter<String> adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<String> data = new ArrayList<>();
data.add("hello world");
ListView listView = findViewById(R.id.list_view);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, data);
listView.setAdapter(adapter);
insertButton = findViewById(R.id.insert_button);
insertButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
adapter.add("hi there");
}
});
}
}

ListView and ArrayAdapter with ConstraintLayout crashes the app

It works perfectly with linear layout but when I choose ConstraintLayout it doesn't work, I don't know why the app crashes
NumbersActivity.java
package com.example.bharat.learnmiwok;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
public class NumbersAct extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_numbers);
ArrayList<String> words = new ArrayList<String>();
words.add("one");
words.add("two");
words.add("three");
words.add("four");
words.add("five");
words.add("six");
words.add("seven");
words.add("eight");
words.add("nine");
words.add("ten");
ArrayAdapter<String> itemsAdapter =
new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, words);
ListView listView = (ListView) findViewById(R.id.list);
listView.setAdapter(itemsAdapter);
}
}
activity_numbers.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.bharat.learnmiwok.MainActivity"
android:id="#+id/list"
android:orientation="vertical">
</android.support.constraint.ConstraintLayout>
Thank you

You need to have a ListView with id list in your layout. Remove/Change the id from your ConstraintLayout, add a listview and try again.
<ListView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
Your ConstraintLayout is not a ListView.

Probably on this line you getting crash
ListView listView = (ListView) findViewById(R.id.list);
You tried to cast ConstraintLayout to ListView

You are using this:
ListView listView = (ListView) findViewById(R.id.list);
to find a ConstraintLayout. Try this instead:
ConstraintLayout listView = (ConstraintLayout) findViewById(R.id.activity_main);
This would only resolve your crash, but it's best to use a listView or contain one into the ConstraintLayout to achieve your goal.

Showing error in ArrayAdapter ListView

I have written this code but it shows me error and i cannot identify where the problem is.My code is as follows-
package com.example.adapterexample;
import android.support.v4.app.Fragment;
import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.os.Build;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listAdapter();
}
public void listAdapter() {
String[] myItems = { "Apple", "Orange", "Grape", "Watermilon" };
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
R.layout.da_items, myItems);
ListView list = (ListView) findViewById(R.id.listView);
list.setAdapter(adapter);
}
}
xml for da_items
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
</LinearLayout>
xml for activity_main
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
//tools:context="com.example.adapterexample.MainActivity"
//tools:ignore="MergeRootFrame" >
<ListView
android:id="#+id/listView"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</FrameLayout>
It shows me error: E/ArrayAdapter(30552): You must supply a resource ID for a TextView
I do not add any text view then why this error is coming?
JavaExperts need your valuable suggestion to solve this issue.

Check official docs of ArrayAdapter.
public ArrayAdapter (Context context, int resource, T[] objects)
Added in API level 1
Constructor
Parameters
context - The current context.
resource - The resource ID for a layout file containing a TextView to use when instantiating views.
objects - The objects to represent in the ListView.
You will notice that the array adapter is expecting that the second parameter is a resource id of a text view not a layout.
So, when you use this constructor:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
R.layout.da_items, myItems);
R.Layout.da_items must be an xml layout where the first element must be a TextView, something like this:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
//other attributes
/>
To be more sort of a custom textview, you can also use -
new ArrayAdapter<String>(this, R.layout.da_items,
R.id.the_id_of_a_textview_from_the_layout, myItems)
where you supply the id of a layout that can contain various views, but also must contain a TextView with and id(third parameter) that you pass to your ArrayAdapter so it can know where to put the Strings.

The layout that you provide in the adapter - R.layout.da_items - should only contain a TextView because that's what android supports by default. So either use android.R.layout.simple_list_item_1 (this layout is provided by android) in place of your custom layout or make sure that your R.layout.da_items looks something like :
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#android:id/text1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:gravity="center_vertical"
android:paddingLeft="6dip"
android:minHeight="?android:attr/listPreferredItemHeight"
/>

Try this.
Add this in da_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="#+id/icon"
android:paddingBottom="10dp"
android:textColor="#CC0033"
android:textSize="16sp" />
</LinearLayout>
And in MainActivity.java
listView = (ListView) findViewById(R.id.list1);
CustomListViewAdapter adapter = new CustomListViewAdapter(this,
R.layout.da_item, myItems);
listView.setAdapter(adapter);

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.simple_list_item_1, myItems);
it will help you.

As you have used below code is creating problem
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
R.layout.da_items, myItems);
So there is no need to make another layout and use it as R.layout.da_items
instead use
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.simple_list_item_1, myItems);

Empty ListView with simple_list_item_multiple_choice layout

How to handle an empty ListView if I use simple_list_item_multiple_choice layout?
'Android Developers' say that I should use the android prefix
android:id="#android:id/empty
But cannot take in mind how to use it with simple_list_item_multiple_choice
protected ListView mFavList;
ArrayList<String> fakeFavs;
mFavList.setAdapter(new ArrayAdapter<String>(this.android.R.layout.simple_list_item_multiple_choice,fakeFavs);
if fakeFavs is null?

I solved my problem.
All I need - "empty" tag in main.xml layout and string of code:
mFavList.setEmptyView(findViewById(android.R.id.empty));
In my program fakeFavs is populating from text file.
In case of empty file, the empty list is properly handled.
Maybe it will be useful for somebody. Working example:
import java.util.ArrayList;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class HelloAndroid3 extends Activity {
/** Called when the activity is first created. */
static final String split_symbol = "\n";
protected ListView mFavList;
protected ArrayList<String> fakeFavs;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
fakeFavs = new ArrayList<String>();
this.mFavList = (ListView) this.findViewById(R.id.list_favorites);
refreshFavListItems();
}
private void refreshFavListItems() {
//put some code here that populates fakeFavs
//.......
mFavList.setAdapter(new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_multiple_choice, fakeFavs));
mFavList.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
mFavList.setEmptyView(findViewById(android.R.id.empty));
//if fakeFavs will be empty, list shows "No Data"
}
}
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="match_parent" >
<ListView android:id="#+id/list_favorites"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1.0"
/>
<TextView android:id="#android:id/empty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#FF0000"
android:text="No Data"/>