java - Open PDF Automatically After Downloaded

Question

I have a webview app that have pdf download feature for downloading pdf file from some different websites. I would like to know how to open the pdf immediately after downloaded. I haven't got a pdf reader in my app yet as I don't know how to applied it.

I have read all the answers for the similar questions I ask but all the answers are not applicable. The problem is the name of pdf is based on what the uploader set, so the name of the pdf file will be different per websites visited.

In the code below, the generated name of the pdf file downloaded is based on the pdf name on the site, not determined by me.

Is it possible to open the pdf file based on the code or should I alter the code?

package com.example.app;

public class WebViewActivity extends AppCompatActivity {

    String url = "";
    NetworkChangeListener networkChangeListener = new NetworkChangeListener();

    private boolean multiple_files = true;

    private static String file_type     = "*/*";
    private ValueCallback<Uri> file_data;
    private ValueCallback<Uri[]> file_path;
    private final static int file_req_code = 1;

    private static final String TAG = WebViewActivity.class.getSimpleName();

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.webview);

        webView = findViewById(R.id.webView);
        WebSettings appwebsettings = webView.getSettings();

        appwebsettings.setLoadsImagesAutomatically(true);
        appwebsettings.setJavaScriptEnabled(true);
        appwebsettings.setAllowContentAccess(true);
        appwebsettings.setAllowFileAccess(true);

        url = getIntent().getStringExtra("URL_NAME");
        webView.loadUrl(url);
        webView.requestFocus();

        webView.setWebViewClient(new WebViewClient(){
            @Override
            public void onPageFinished(WebView view, String url) {
                swipeRefreshLayout.setEnabled(false);
                super.onPageFinished(view, url);
            }

            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                view.loadUrl(url);
                return true;
            }
        });

        webView.setWebChromeClient(new WebChromeClient(){
            @Override
            public void onReceivedTitle(WebView view, String title) {
                super.onReceivedTitle(view, title);
            }

            @Override
            public void onReceivedIcon(WebView view, Bitmap icon) {
                super.onReceivedIcon(view, icon);
            }
        });

        if(Build.VERSION.SDK_INT>= Build.VERSION_CODES.M){
            if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)== PackageManager.PERMISSION_DENIED){
                Log.d("permission", "permission denied to WRITE_EXTERNAL_STORAGE - requesting it");
                String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
                requestPermissions(permissions,1);
            }
        }

        webView.setDownloadListener(new DownloadListener() {
            @Override
            public void onDownloadStart(String url, String userAgent, String contentDisposition,
                                        String mimeType, long contentLength) {
                DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
                request.setMimeType(mimeType);
                String cookies = CookieManager.getInstance().getCookie(url);
                request.addRequestHeader("cookie",cookies);
                request.addRequestHeader("User-Agent",userAgent);
                request.setDescription("Downloading File");
                request.setTitle(URLUtil.guessFileName(url,contentDisposition,mimeType));
                request.allowScanningByMediaScanner();
                request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
                request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,
                        URLUtil.guessFileName(url, contentDisposition, mimeType));
                DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
                downloadManager.enqueue(request);
                Toast.makeText(getApplicationContext(), "Downloading File", Toast.LENGTH_SHORT).show();
            }
        });

    @Override
    protected void onStart() {
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(networkChangeListener, filter);
        super.onStart();
    }

    @Override
    protected void onStop() {
        unregisterReceiver(networkChangeListener);
        super.onStop();
    }

    @Override
    public void onBackPressed() {
        if(webView.canGoBack()){
            webView.goBack();
        }else {
            finish();
            super.onBackPressed();
        }
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig){
        super.onConfigurationChanged(newConfig);
    }
}

This is my Webview 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"
    android:orientation="vertical"
    tools:context=".WebViewActivity">
    
    <WebView
            android:id="@+id/webView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

</LinearLayout>

Thank you in advance.

Answer 1

Thanks to @blackapps for the suggestion.

I found out that the answer of my silly question is quite simple.

I insist in using URLUtil.guessFileName(url,contentDisposition,mimeType)) because when I download the pdf file, the downloaded filename will be the same with the uploaded filename in my client's website.

So what I just did is adding this equation fileName = URLUtil.guessFileName(url,contentDisposition,mimeType)) and register receiver in Download Manager then create the reaction after pdf download is completed.

public class WebViewActivity extends AppCompatActivity {

...

    private String fileName;
    
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        ...
        
        webView.setDownloadListener(new DownloadListener() {
        @Override
        public void onDownloadStart(String url, String userAgent, String contentDisposition,
                                    String mimeType, long contentLength) {
            DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
            //setup the fileName
            fileName = URLUtil.guessFileName(url,contentDisposition,mimeType);
            
            request.setMimeType(mimeType);
            String cookies = CookieManager.getInstance().getCookie(url);
            request.addRequestHeader("cookie",cookies);
            request.addRequestHeader("User-Agent",userAgent);
            request.setDescription("Downloading File");
            request.setTitle(fileName));
            request.allowScanningByMediaScanner();
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,
                    fileName);
            DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
            //Registering receiver in Download Manager
            registerReceiver(onCompleted, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));    
            downloadManager.enqueue(request);
            Toast.makeText(getApplicationContext(), "Downloading File", Toast.LENGTH_SHORT).show();
        }
        
    });
    
    ...
    
    BroadcastReceiver onCompleted = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context.getApplicationContext(), "Download Finish", Toast.LENGTH_SHORT).show();
            File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/" + fileName);
            Uri uri = FileProvider.getUriForFile(WebViewActivity.this, "com.example.app"+".provider",file);
            Intent i = new Intent(Intent.ACTION_VIEW);
            i.setDataAndType(uri, "application/pdf");
            i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_GRANT_READ_URI_PERMISSION);
            startActivity(i);
        }
    };
}