1

我是 android 新手我想images从网上下载到我的模拟器我已经看到 了这个，我的问题也是如此。但我已经这样做了：

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    new MyAsnyc().execute();
}   

public class MyAsnyc extends AsyncTask<Void, Void,Void>{
    public  File file ;
    InputStream is;
    protected void inBackground() 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(BASE_URL);
            /* Open a connection to that URL. */
            URLConnection ucon = url.openConnection();

            /*
             * Define InputStreams to read from the URLConnection.
             */
            is = ucon.getInputStream();

            OutputStream os = new FileOutputStream(file);
            byte[] data = new byte[is.available()];
            is.read(data);
            Log.d("MY_TAG>>>", "Picture is Readable...");
            os.write(data);
            Log.d("MY_TAG>>>", "Picture is Saved...");
            is.close();
            os.close();

        }
        catch (IOException e) {
            Log.d("ImageManager", "Error: " + e);
        }
    }
    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

        try {
            inBackground();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }
    protected void onPostExecute()
    {

        try
        {
            // 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 (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

}

但我AsyncTask从来没有打电话请任何人帮助我如何解决这个问题以及如何从网上下载图像。

4

3 回答 3

2

您正在doInBackground(Void... params)递归调用而不是调用doInBackground(). 将后者重命名为其他名称并从doInBackground(Void... params).

于 2013-03-09T08:02:24.677 回答
0

像这样在 doInBackground 中执行所有操作：

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

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

      try{
      File path = Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES);
       file = new File(path, "DemoPicture.jpg");

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

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

              /*
               * Define InputStreams to read from the URLConnection.
               */
              is = ucon.getInputStream();

              OutputStream os = new FileOutputStream(file);
              byte[] data = new byte[is.available()];
              is.read(data);
              Log.d("MY_TAG>>>", "Picture is Readable...");
              os.write(data);
              Log.d("MY_TAG>>>", "Picture is Saved...");
              is.close();
              os.close();

          }
          catch (IOException e) {
              Log.d("ImageManager", "Error: " + e);
          }

        return null;
    }

  protected void onPostExecute()
   {

    try
    {
        // 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 (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

  }

 }
于 2013-03-09T09:45:06.310 回答
0

行！要将图像下载到您的设备/模拟器，您应该试试这个！！

首先创建一个Class：

public class DownloadImage {    

public static File getImage(String imageUrl, String fileName){
    File file = null;
    try {
        //set the download URL, a url that points to a file on the internet
        //this is the file to be downloaded         
        URL url = new URL(imageUrl);
        Log.d("INFORMATION..", "FILE FOUNDED....");
        //create the new connection
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        //set up some things on the connection
        urlConnection.setRequestMethod("GET");
        urlConnection.setDoOutput(true);

        //and connect!
        urlConnection.connect();
        Log.d("INFORMATION..", "FILE CONECTED....");
        //set the path where we want to save the file
        //in this case, going to save it on the root directory of the
        //sd card.
        File SDCardRoot = Environment.getExternalStorageDirectory();
        //create a new file, specifying the path, and the filename
        //which we want to save the file as.
        file = new File(SDCardRoot, fileName);

        //this will be used to write the downloaded data into the file we created
        FileOutputStream fileOutput = new FileOutputStream(file);
        Log.d("INFORMATION..", "WRINTING TO FILE DOWNLOADED...." + file);
        //this will be used in reading the data from the internet
        InputStream inputStream = urlConnection.getInputStream();

        //this is the total size of the file
        int totalSize = urlConnection.getContentLength();
        //variable to store total downloaded bytes
        int downloadedSize = 0;

        //create a buffer...
        byte[] buffer = new byte[1024];
        int bufferLength = 0; //used to store a temporary size of the buffer

        //now, read through the input buffer and write the contents to the file
        while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
            //add the data in the buffer to the file in the file output stream (the file on the sd card
            fileOutput.write(buffer, 0, bufferLength);
            //add up the size so we know how much is downloaded
            downloadedSize += bufferLength;
            Log.d("INFORMATION..", "FILE DOWNLOADED....");
            //this is where you would do something to report the prgress, like this maybe
            //updateProgress(downloadedSize, totalSize);

        }
        //close the output stream when done
        fileOutput.close();
        Log.d("INFORMATION..", "FILE DOWNLOADING COMPLETED....");
        //catch some possible errors...
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return file;
}
)

DownloadImage.getImage(String imageUrl, String fileName)像这样调用MainActivity.java它：

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ImageView imageView = (ImageView) findViewById(R.id.imageView1);

    String url = "http://4.bp.blogspot.com/-8v_k_fOcfP8/UQIL4ufghBI/AAAAAAAAEDo/9ffRRTM9AnA/s1600/android-robog-alone.png"; 

    String file = DownloadImage.getImage(url, "My Image.jpg").toString();

    // Get file path on device and set it to imageView
    Bitmap bitmap = BitmapFactory.decodeFile(file);
    imageView.setImageBitmap(bitmap);
}
}

我希望这将根据您的需要工作！

于 2013-03-09T18:52:40.227 回答