为什么我的webview应用程序下载.bin文件？

所以我为webmail构建了这个应用程序但是当我想下载附件（邮件中的文件）时没有任何反应 . 今天我在MainActivity.java中插入了这段代码：

myWebView.setDownloadListener(new DownloadListener() {
        @Override
        public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype, long contentLength) {

            DownloadManager.Request myRequest = new DownloadManager.Request(Uri.parse(url));
            myRequest.allowScanningByMediaScanner();
            myRequest.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

            DownloadManager myManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
            myManager.enqueue(myRequest);
        }
    });

之后我的文件以.bin扩展名下载，没有原始文件名 . 我在android清单中添加了这些权限：

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

这是MainActivity.java的完整代码：

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("https://webmail.carnet.hr/login.php");
    myWebView.setWebViewClient(new WebViewClient());
    myWebView.getSettings().setBuiltInZoomControls(true);

    myWebView.setDownloadListener(new DownloadListener() {
        @Override
        public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype, long contentLength) {

            DownloadManager.Request myRequest = new DownloadManager.Request(Uri.parse(url));
            myRequest.allowScanningByMediaScanner();
            myRequest.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

            DownloadManager myManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
            myManager.enqueue(myRequest);
        }
    });










}

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

}

我真的想完成这个应用程序，所以如果你有任何sugestions或想要帮助请做！