HTTP get request is missing data

问题

Hi i have a strange problem with HTTP in Android. I'm trying to get a picture from a remote server and display it on the device. If the picture is a small JPEG, this is not a problem. but if the picture get bigger in size it will not work (only parts of the picture are shown).

Here is my complete demo code:

public class HTTP_testActivity extends Activity {

private ImageView ivPicture;
private Button btGetImage;  


/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    ivPicture = (ImageView) findViewById(R.id.ivpiture1);
    btGetImage = (Button) findViewById(R.id.btGetPicture1);
    btGetImage.setOnClickListener(new Button.OnClickListener() 
    {
        public void onClick(View arg0) 
        {
            URI uri;
            try {


                uri = new URI("");
                URLConnection connection =  uri.toURL().openConnection();
                connection.setUseCaches(true);
                connection.connect();

                BufferedInputStream bis = new BufferedInputStream(connection.getInputStream());
                Log.d("TEST","Length of Input " +bis.available());
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                Log.d("TEST","Length of Input after wait " +bis.available());
                byte[] data = new byte[640*480*5];
                bis.read(data);
                Bitmap bmp = BitmapFactory.decodeByteArray(data, 0, jdata.length);
                if (bmp != null)
                {
                    ivPicture.setImageBitmap(bmp);
                }
                bis.close();
        } catch (URISyntaxException e) {
            // TODO Auto-generated catch block
            Log.d("TEST", e.getMessage());
            e.printStackTrace();
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            Log.d("TEST", e.getMessage());
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            Log.d("TEST", e.getMessage());
            e.printStackTrace();
        }
        }
    });
}

Can someone see what I'm doing wrong? What I have figured out so far is: bis.available() returns never more than 65kb. Although the InputStream itself has the right length (seen in the debugger).

回答1:

available()

will return the number of bytes that con be read from the inputstream without blocking. So it will be return data that could be read from the network without blocking.

try with:

            InputStream bis = new InputStream(connection.getInputStream());
            Log.d("TEST","Length of Input " +bis.available());
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            int read = 0;
            byte[] buffer = new byte[SIZE_OF_IMAGE];
            byte[] inBuff = new byte[32678]
            while ((read = bis.read(inBuff, 0, 32768)) > 0) {
                   // copy in buffer what have been read
                   // from the input stream
            }

            // close the is
            Bitmap bmp = BitmapFactory.decodeByteArray(buffer, 0, buffer.length);

obviously is not there are more efficient way to do this but could be an entry point. Let me know if you need more help.

Edit: of course you have to avoid doing blocking call in the UI thread, as people have suggested.

回答2:

Thinks you need to Know bis.available() will always return less than 65Kb because Max IP Packet size is 65535 bytes. InputStream will return you the Total Size

As you have gave only one read Statement at any point of time data array will always be less than 65kb. (i.e. Data of first Packet)

What you can do is use BitmapFactory.decodeStream(InputStream is) and give the InputStream bis it will read all the bytes in the Stream and give you the Bitmap

EDITED

USE THIS FUNCTION

this will give you all the Bytes from InputStream

 public static byte[] ReadToEOF(InputStream stream) throws Exception
    {
        try {
            ByteArrayOutputStream array = new ByteArrayOutputStream();
            int read = 0;
            byte[] receivedData = new byte[5000];
            while((read = stream.read(receivedData)) > 0)
            {
                array.write(receivedData, 0, read);
                if(!(stream instanceof FileInputStream) && stream.available() == 0)
                {
                    try {
                        Thread.sleep(1000);
                    } catch (Exception e) {
                        // TODO: handle exception
                    }
                    if(stream.available() == 0)
                        break;
                }
            }
            return array.toByteArray();
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        }
    }

Thread.Sleep is because to get Next Packet through Internet there can be some delay

来源：https://stackoverflow.com/questions/9720381/http-get-request-is-missing-data