how to download image from server in android studio. using Download manager

need permission

<uses-permission android:name="android.permission.INTERNET"/>

import android.annotation.SuppressLint;
import android.app.DownloadManager;
import android.content.Context;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    Button down;
    DownloadManager downloadManager;

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        down = (Button)findViewById(R.id.downloadFile);
        down.setOnClickListener(new View.OnClickListener() {
             
            @Override            public void onClick(View v) {
                downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
                Uri uri = Uri.parse("http://mandsit.com/amirul/assets/just/just_result.pdf");
               DownloadManager.Request request = new DownloadManager.Request(uri);
                request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
                Long reference = downloadManager.enqueue(request);


            }
        });
    }
}









<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.edupointbd.amirul.myapplication.MainActivity">


    <Button        android:text="donload file"        android:id="@+id/downloadFile"        android:layout_width="match_parent"        android:layout_height="wrap_content" />

</RelativeLayout>