如何将文件/图像从 url 下载到您的 android 应用程序 [英] How to download file/image from url to your android app

问题描述

我需要我的 android 应用程序向 url 发出请求以从此 url 下载图像所以我建立了这个类来帮助我，但它没有用???

I need my android app to make request to url to download an image from this url so I have built this class to help me, BUT it didn't work ???

public class MyAsnyc extends AsyncTask<Void, Void, Void> {
public static File file;
InputStream is;

    protected void doInBackground() throws IOException {
        File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        file = new File(path, "DemoPicture.jpg");

        try{
            // Make sure the Pictures directory exists.
            path.mkdirs();

            URL url = new URL("http://androidsaveitem.appspot.com/downloadjpg");

            // Open a connection to that URL.
            URLConnection ucon = url.openConnection();

            // Define InputStreams to read from the URLConnection.
            is = ucon.getInputStream();
        } catch (IOException e) {
            Log.d("ImageManager", "Error: " + e);
        }
    }

    @Override
    protected Void doInBackground(Void... params) {
        try {
            doInBackground();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }

    protected void onPostExecute() {
        try {
            OutputStream os = new FileOutputStream(file);
            byte[] data = new byte[is.available()];
            is.read(data);
            os.write(data);
            is.close();
            os.close();

            // Tell the media scanner about the new file so that it is
            // immediately available to the user.
            MediaScannerConnection.scanFile(
                null,
                new String[] { file.toString() },
                null,
                new MediaScannerConnection.OnScanCompletedListener() {
                    public void onScanCompleted(String path, Uri uri) {
                        Log.i("ExternalStorage", "Scanned " + path + ":");
                        Log.i("ExternalStorage", "-> uri=" + uri);
                    }
                }
            );
        }
        catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

而且我在 onclick() 的 Activity 类中有这个函数:

And I have, in the Activity class on onclick(), this function:

public void down(View v) {
    // ImageManager ob=new ImageManager();
    // ob.DownloadFromUrl("");

     new MyAsnyc().execute();
}

虽然我在manfiest.xml中写了权限

Although I have written the permissions in the manfiest.xml

<uses-sdk android:minSdkVersion="7" />
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

推荐答案

在顶部定义这些

Button BtnDownload;

DownloadManager downloadManager;

之后，你应该在里面写:

After, You should write on create inside :

BtnDownload = (Button)findViewById(R.id.button1);

稍后，您应该写入按钮的点击事件

Later, You should write to the button's click event

downloadManager = (DownloadManager)getSystemService(Context.DOWNLOAD_SERVICE);

Uri uri = Uri.parse("your url");

DownloadManager.Request request = new DownloadManager.Request(uri);
                request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

Long reference = downloadManager.enqueue(request);

最后，您需要将其添加到 manifest.xml 的应用程序标记中:

Finally, you need to add this onto the application tag to the manifest.xml :

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

这篇关于如何将文件/图像从 url 下载到您的 android 应用程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！