如何从Android webview下载文件？

我下面的代码可以很好地加载 url 页面，并且在搜索歌曲后，当我单击下载链接时，它崩溃了。关于如何让下载管理器与网络视图一起工作的教程并不多。我究竟做错了什么？

import java.io.File;
import android.app.Activity;
import android.app.DownloadManager;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.webkit.WebView;
import android.webkit.WebViewClient;


public class List1 extends Activity {

        WebView ourBrow;


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

        // Use a custom layout file
        setContentView(R.layout.list1);

        final DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);

     final File destinationDir = new File (Environment.getExternalStorageDirectory(), getPackageName());
     if (!destinationDir.exists()) {
         destinationDir.mkdir(); // Don't forget to make the directory if it's not there
     }

        ourBrow = (WebView) findViewById(R.id.wvBrowser);
        ourBrow.getSettings().setJavaScriptEnabled(true);
        ourBrow.setInitialScale(50); 
        ourBrow.getSettings().setUseWideViewPort(true); 
        ourBrow.setVerticalScrollBarEnabled(false);
        ourBrow.setHorizontalScrollBarEnabled(false);
        ourBrow.loadUrl("http://www.degjo.com");



        ourBrow.setWebViewClient(new WebViewClient() {
            @Override
            public boolean shouldOverrideUrlLoading (WebView view, String url) {
                boolean shouldOverride = false;
                // We only want to handle requests for mp3 files, everything else the webview
                // can handle normally
                if (url.endsWith(".mp3")) {
                    shouldOverride = true;
                    Uri source = Uri.parse(url);

                    // Make a new request pointing to the mp3 url
                    DownloadManager.Request request = new DownloadManager.Request(source);
                    // Use the same file name for the destination
                    File destinationFile = new File (destinationDir, source.getLastPathSegment());
                    request.setDestinationUri(Uri.fromFile(destinationFile));
                    // Add it to the manager
                    manager.enqueue(request);
                }
                return shouldOverride;
            }
        });





    }
}

LogCat

02-18 19:45:44.891: E/AndroidRuntime(357):  at android.content.ContentProviderProxy.insert(ContentProviderNative.java:408)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.content.ContentResolver.insert(ContentResolver.java:604)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.app.DownloadManager.enqueue(DownloadManager.java:750)
02-18 19:45:44.891: E/AndroidRuntime(357):  at com.example.androidbuttonsactivities.List1$1.shouldOverrideUrlLoading(List1.java:78)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.webkit.CallbackProxy.uiOverrideUrlLoading(CallbackProxy.java:216)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.webkit.CallbackProxy.handleMessage(CallbackProxy.java:323)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.os.Handler.dispatchMessage(Handler.java:99)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.os.Looper.loop(Looper.java:123)
02-18 19:45:44.891: E/AndroidRuntime(357):  at android.app.ActivityThread.main(ActivityThread.java:3683)
02-18 19:45:44.891: E/AndroidRuntime(357):  at java.lang.reflect.Method.invokeNative(Native Method)
02-18 19:45:44.891: E/AndroidRuntime(357):  at java.lang.reflect.Method.invoke(Method.java:507)
02-18 19:45:44.891: E/AndroidRuntime(357):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-18 19:45:44.891: E/AndroidRuntime(357):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-18 19:45:44.891: E/AndroidRuntime(357):  at dalvik.system.NativeStart.main(Native Method)
02-18 19:45:48.401: I/Process(357): Sending signal. PID: 357 SIG: 9

这可能取决于 android 版本问题，下面的代码将在 2.3+ 版本上成功运行，检查一下，

ourBrow.setWebViewClient(new WebViewClient() {
        @Override
        public void onReceivedError(WebView view, int errorCode,
            String description, String failingUrl) {
                Log.d("WEB_VIEW_TEST", "error code:" + errorCode + " - " + description);
        }

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
                // handle different requests for different type of files
                // this example handles downloads requests for .apk and .mp3 files
                // everything else the webview can handle normally
                if (url.endsWith(".apk")) {
                    Uri source = Uri.parse(url);
                    // Make a new request pointing to the .apk url
                    DownloadManager.Request request = new DownloadManager.Request(source);
                    // appears the same in Notification bar while downloading
                    request.setDescription("Description for the DownloadManager Bar");
                    request.setTitle("YourApp.apk");
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
                        request.allowScanningByMediaScanner();
                        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
                    }
                    // save the file in the "Downloads" folder of SDCARD
                    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "SmartPigs.apk");
                    // get download service and enqueue file
                    DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
                    manager.enqueue(request);
                }
                else if(url.endsWith(".mp3")) {
                    // if the link points to an .mp3 resource do something else
                }
                // if there is a link to anything else than .apk or .mp3 load the URL in the webview
                else view.loadUrl(url);
                return true;                
        }
    });