PDF 未获取下载表单 URL

Question

我对安卓很陌生，第一次这样做。我正在尝试在我的应用程序中下载 pdf 表单 url，但它没有被下载。我真的搞砸了。我不知道我错过了什么，为什么这对我不起作用。请帮我做到这一点。

在这里，我粘贴了我的代码：

public class ProductBrochureActivity extends Activity {
private static String cookie;
private static String nid;
WebView webViewForBrochureAndVideo;
private String prodBrochureURL;
private String prodVideoURL;
private static int clickedItemId;
ActionBar actionBar;
private static HashMap<String, String> cookieWithRequest = new HashMap<String, String>();
static Object json;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.product_brochure);
    actionBar = getActionBar();
    actionBar.hide();
    Intent intent = getIntent();
    cookie = intent.getStringExtra(BsharpConstant.WEB_SERVICES_COOKIES);
    nid = intent.getStringExtra(BsharpConstant.PRODUCT_NODE_ID);
    clickedItemId = intent.getIntExtra(BsharpConstant.CLICKED_ITEM_ID, 0);
    String jsonResponseFromWebservices = WebserviceBsharpUtil
            .callWebServicesToGetTheProductBrochureAndVideo(cookie, nid);
    urlFromResponse(jsonResponseFromWebservices);
    cookieWithRequest.put(BsharpConstant.WEB_SERVICES_COOKIES, cookie);
    switch (clickedItemId) {
    case 0:
        if (!prodBrochureURL.isEmpty()) {
            try {
                new DownloadFile();
            } catch (ActivityNotFoundException e) {
                Toast.makeText(this,
                        "No Application Available to View PDF",
                        Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "No PDF is Attached with this Product",
                    Toast.LENGTH_SHORT).show();
        }
        break;
    case 1:
        if (!prodVideoURL.isEmpty()) {
            try {
                new DownloadFile();
            } catch (ActivityNotFoundException e) {
                Toast.makeText(this,
                        "No Application Available to View PDF",
                        Toast.LENGTH_SHORT).show();
            }
            break;
        } else {
            Toast.makeText(this, "No Video is Attached with this Product",
                    Toast.LENGTH_SHORT).show();
        }
    }
}
/**
 * GetTheBrochureAndAttachedVideoURL
 * 
 * @param jsonResponse
 */
public void urlFromResponse(String jsonResponse) {
    try {
        json = new JSONTokener(jsonResponse).nextValue();
        if (json instanceof JSONArray) {
            JSONArray jsonArray = (JSONArray) json;
            prodBrochureURL = jsonArray.getJSONObject(0).getString(
                    BsharpConstant.PRODUCT_BROCHURE_URL);
            prodVideoURL = jsonArray.getJSONObject(0).getString(
                    BsharpConstant.PRODUCT_VIDEO_URL);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}
private class DownloadFile extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... params) {
        String filename = "brochure.pdf";
        HttpURLConnection connection;
        try {
            URL url = new URL(prodBrochureURL);
            connection = (HttpURLConnection) url.openConnection();
            connection.addRequestProperty(
                    BsharpConstant.WEB_SERVICES_COOKIES, cookie);
            connection.setDoOutput(true);
            connection.connect();
        } catch (IOException e1) {
            return e1.getMessage();
        }
        File folderDir = new File(getExternalFilesDir("Bsharp_PDF")
                + "/Download");
        File file = new File(folderDir, filename);
        if (file.exists()) {
            file.delete();
        }
        if ((folderDir.mkdirs() || folderDir.isDirectory())) {
            try {
                InputStream inputStream = connection.getInputStream();
                FileOutputStream fileOutputStream = new FileOutputStream(
                        folderDir + "/" + filename);
                byte[] buffer = new byte[1024];
                int len1 = 0;
                while ((len1 = inputStream.read(buffer)) != -1) {
                    fileOutputStream.write(buffer, 0, len1);
                }
                fileOutputStream.close();
                inputStream.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        } else {
            Toast.makeText(getApplicationContext(),
                    "Unable to create folder", Toast.LENGTH_LONG).show();
        }
        return "Done";
    }
    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG)
                .show();
        super.onPostExecute(result);
    }
}

}

Answer 1

为了执行AsyncTask（在你的例子中是DownloadFile），必须显式调用它的execute（Params...参数）方法。在您的情况下，除了实例化您的任务调用之外，执行而不提供任何参数，即

DownloadFile task = new DownloadFile();
task.execute();

希望这有帮助。