How to use comparator interface for Listview in Android?

This example demonstrate about How to use comparator interface for Listview in Android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?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">    <EditText       android:id = "@+id/name"       android:layout_width = "match_parent"       android:hint = "Enter Name"       android:layout_height = "wrap_content" />    <LinearLayout       android:layout_width = "wrap_content"       android:layout_height = "wrap_content">       <Button          android:id = "@+id/save"          android:text = "Save"          android:layout_width = "wrap_content"          android:layout_height = "wrap_content" />       <Button          android:id = "@+id/refresh"          android:text = "Refresh"         android:layout_width = "wrap_content" android:layout_height = "wrap_content" /> </LinearLayout> <ListView android:id = "@+id/listView" android:layout_width = "match_parent" android:layout_height = "wrap_content"> </ListView> </LinearLayout>

In the above code, we have taken name and record number as Edit text, when user click on save button it will store the data into arraylist. Click on refresh button to get the changes of listview.

Step 3 − Add the following code to src/MainActivity.java

package com.example.andy.myapplication; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.ArrayAdapter; import android.widget.EditText; import android.widget.ListView; import android.widget.Toast; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.HashSet; import java.util.Set; public class MainActivity extends AppCompatActivity {    EditText name;    ArrayAdapter arrayAdapter;    ArrayList<String> array_list;    Set set = new HashSet();    private ListView listView;    @Override    protected void onCreate(Bundle readdInstanceState) {    super.onCreate(readdInstanceState);       setContentView(R.layout.activity_main);       array_list = new ArrayList<String>();       name = findViewById(R.id.name);       listView = findViewById(R.id.listView);       findViewById(R.id.refresh).setOnClickListener(new View.OnClickListener() {          @Override          public void onClick(View v) {             arrayAdapter.notifyDataSetChanged();             listView.invalidateViews();             listView.refreshDrawableState();          }       });       findViewById(R.id.save).setOnClickListener(new View.OnClickListener() {          @Override          public void onClick(View v) {             if (!name.getText().toString().isEmpty()) {                set.add(name.getText().toString());                array_list.clear();                array_list.addAll(set);                Collections.sort(array_list, new Comparator<String>() {                   @Override                   public int compare(String o1, String o2) {                      return o1.compareTo(o2);                   }                });                arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, array_list);                listView.setAdapter(arrayAdapter);                Toast.makeText(MainActivity.this, "Inserted", Toast.LENGTH_LONG).show();             } else {                name.setError("Enter NAME");             }          }       }); } }

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –

In the above result, we are inserting value as abc and check listview it is storing value in middle of sairam and a.

Click here to download the project code