Downloading PDF files in internal storage

Only your own app can Access to app internal storage Default android builtin download manager cant access to your app internal storage so you cant download in internal storage.

Solution:

Download file in sd card as a temp file and when download complete register a receiver and then copy file from external to internal storage after copy delete file from external storage.

Complete code:

public class MainActivity extends Activity {
    private long enqueue;
    private DownloadManager dm;

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        BroadcastReceiver receiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                    long downloadId = intent.getLongExtra(
                            DownloadManager.EXTRA_DOWNLOAD_ID, 0);
                    DownloadManager.Query query = new DownloadManager.Query();
                    query.setFilterById(enqueue);
                    Cursor c = dm.query(query);
                    if (c.moveToFirst()) {
                        int columnIndex = c
                                .getColumnIndex(DownloadManager.COLUMN_STATUS);
                        if (DownloadManager.STATUS_SUCCESSFUL == c
                                .getInt(columnIndex)) {

                            ImageView view = (ImageView) findViewById(R.id.imageView1);
                            String uriString = c
                                    .getString(c
                                            .getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));

                            Uri a = Uri.parse(uriString);
                            File d = new File(a.getPath());
                           // copy file from external to internal storage..After that delete file from external storage..Code will easily avalible on google.
                            view.setImageURI(a);
                        }
                    }
                }
            }
        };

        registerReceiver(receiver, new IntentFilter(
                DownloadManager.ACTION_DOWNLOAD_COMPLETE));
    }

    public void onClick(View view) {
        dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
        DownloadManager.Request request = new DownloadManager.Request(
                Uri.parse("http://www.vogella.de/img/lars/LarsVogelArticle7.png")).setDestinationInExternalPublicDir("/Sohail_Temp", "test.jpg");
        enqueue = dm.enqueue(request);
    }

    public void showDownload(View view) {
        Intent i = new Intent();
        i.setAction(DownloadManager.ACTION_VIEW_DOWNLOADS);
        startActivity(i);
    }
}

Layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onClick"
        android:text="Start Download"></Button>

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="showDownload"
        android:text="View Downloads"></Button>

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/image_1"></ImageView>
</LinearLayout>

Permissions:

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

You cannot use DownloadManager to download directly to your app's portion of internal storage. You will need to use OkHttp or some other in-process HTTP client API.