Need help for my android web application

So i made an app for my school's website, the problem is, that my app can not download files if it is linked or uploaded on the website. I am pretty new to coding so i dont know much, so can someone guide me the set of codes required to download files from my app. I am using android studio, thanks

This is the main activity file import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.webkit.WebSettings; import android.webkit.WebView; import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {
private WebView mywebview;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mywebview = (WebView) findViewById(R.id.webview);
    WebSettings websettings = mywebview.getSettings();
    websettings.setJavaScriptEnabled(true);
    mywebview.loadUrl("http://ift.tt/2buKaIo" );
    mywebview.setWebViewClient(new WebViewClient());
    WebSettings webSettings = mywebview.getSettings();
    webSettings.setJavaScriptEnabled(true);


 }
 public void onBackPressed() {
    if(mywebview.canGoBack()){
        mywebview.goBack();

    } else {

    }
    super.onBackPressed();
   }
    public void onWindowFocusChanged(boolean hasFocus){
    super.onWindowFocusChanged(hasFocus);
    View decorView = getWindow().getDecorView();
    if(hasFocus){
        decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE
        | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
        | View.SYSTEM_UI_FLAG_FULLSCREEN
        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN );
    }

    }