Android Webview not triggering a href download file

问题

I have added the Download Manager , but it is not triggering the download event , can any body help . When user goes to webview download option and click a link to download a file nothing happens. I have gone through many of the post in stackoverflow but nothing works for me.

 public class MainActivity extends AppCompatActivity {

    private WebView mWebView;

    // boolean thread_running = true;
    private static final String TAG = "MainActivity";
    // flag for Internet connection status
    Boolean isInternetPresent = false;

    // Connection detector class
    ConnectionDetector cd;


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


        mWebView = (WebView) findViewById(R.id.webView);
        mWebView.setWebViewClient(new MyAppWebViewClient(this));

        WebSettings webSettings = mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setSupportZoom(false);
        webSettings.setDomStorageEnabled(true);


        // creating connection detector class instance
        cd = new ConnectionDetector(getApplicationContext());
        /**
         * Check Internet status button click event
         * */
        isInternetPresent = cd.isConnectingToInternet();
        // check for Internet status
        if (isInternetPresent) {
            // Internet Connection is Present
            // make HTTP requests
            mWebView.loadUrl("http://url");
        } else {
            // Internet connection is not present
            // Ask user to connect to Internet
            //showAlertDialog(MainActivity.this, "No Internet Connection",
            //"You don't have internet connection.", false);
            Toast.makeText(this, "No Internet connection, Please SwitchOn Connection", Toast.LENGTH_LONG).show();
            finish();
        }

    }

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


    public class MyAppWebViewClient extends WebViewClient {

        private Context context;

        public MyAppWebViewClient(Context context) {
            this.context = context;
        }

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {

            if (!cd.isConnectingToInternet()) {

                //internet is not present
                Toast.makeText(getApplicationContext(), "Internet Stopped Working", Toast.LENGTH_SHORT).show();
                finish();
            }

            if(url.contains(".JPG")){

                DownloadManager mdDownloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
                DownloadManager.Request request = new DownloadManager.Request(
                        Uri.parse(url));
                File destinationFile = new File(Environment.getExternalStorageDirectory(),getFileName(url));
                request.setDescription("Downloading ...");
                request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
                request.setDestinationUri(Uri.fromFile(destinationFile));
                mdDownloadManager.enqueue(request);


                return true;

            }

            view.loadUrl(url);
            return true;
        }

        public String getFileName(String url) {
            String filenameWithoutExtension = "";
            filenameWithoutExtension = String.valueOf(System.currentTimeMillis()
                    + ".jpg");
            return filenameWithoutExtension;
        }

    }
    }

Can someone help me out here? The page loads without issue but the link to a image file in the HTML page is not working...

I am getting this following error when click on link

 Writing exception to parcel
                                                                java.lang.SecurityException: No permission to write to /storage/emulated/0/1499148267411.jpg: Neither user 10109 nor current process has android.permission.WRITE_EXTERNAL_STORAGE.
                                                                    at android.app.ContextImpl.enforce(ContextImpl.java:1438)
                                                                    at android.app.ContextImpl.enforceCallingOrSelfPermission(ContextImpl.java:1470)
                                                                    at com.android.providers.downloads.DownloadProvider.checkFileUriDestination(DownloadProvider.java:724)
                                                                    at com.android.providers.downloads.DownloadProvider.insert(DownloadProvider.java:558)
                                                                    at android.content.ContentProvider$Transport.insert(ContentProvider.java:263)
                                                                    at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:163)
                                                                    at android.os.Binder.execTransact(Binder.java:453)

回答1:

Finally after searching lot and reading here about permission in Marshmallow API 23 >= , we need to give permission in run time . I solved my problem with this code ,

Oncreate method in MainActivity

   int permissionCheck = ActivityCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE);
    if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
        //requesting permission
        ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
    } else {
        Log.i(TAG , "Permission Granted");
    }

and Overriding this Method

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if(grantResults[0]== PackageManager.PERMISSION_GRANTED){
        //you have the permission now.
            Log.i(TAG , "Permission Already Granted");
    }


}

回答2:

add these two lines in your mainfest file

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

回答3:

Can you show the line in the html (the link from where you download) like:

<a href='something'></a>

or do you use js to trigger it?

Because if you want you can use this:

Example

Download file when clicking on the link (instead of navigating to the file):

<a href="/images/myw3schoolsimage.jpg" download>

see this link for more info

UPDATE

add this to your AndroidManifest.xml

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

EDIT

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="********">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

来源：https://stackoverflow.com/questions/44882785/android-webview-not-triggering-a-href-download-file