Android BinaryFactory.decodeStream始終返回null

Question

我正在嘗試下載圖像並使用BitmapFactory將其解碼為位圖，但encodeStream始終返回null。 我在Google上搜索了許多類似的問題，嘗試了許多示例，但沒有找到解決方案。

這是我的代碼：

    public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void downloadButton(View v)
    {
        String imageUrl = "http://www.picgifs.com/bird-graphics/bird-graphics/elf-owl/bird-graphics-elf-owl-527150.bmp";
        new Thread(new ImageDownloader(imageUrl)).start();
    }

    public void showImageButton(View v)
    {
        Bitmap image = ImageHandler.getImage();
        if (image == null)
            Log.e("Error", "No image available");
        else {
            ImageView imageView = (ImageView)findViewById(R.id.ImageView);
            imageView.setImageBitmap(image);
        }
    }
}

class ImageHandler
{
    static protected List<Bitmap> imagesList;
    static public void addImage(Bitmap image)
    {
        imagesList.add(image);
    }
    static public Bitmap getImage()
    {
        if (!imagesList.isEmpty())
            return imagesList.get(0);
        else
            return null;
    }
}

class ImageDownloader implements Runnable
{
    public Bitmap bmpImage;
    private String urlString;
    public ImageDownloader(String urlString)
    {
        this.urlString = urlString;
    }
    public void run()
    {
        try
        {
            AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
            HttpGet getRequest = new HttpGet(urlString);
            HttpResponse response = client.execute(getRequest);
            HttpEntity entity = response.getEntity();
            InputStream inputStream = null;
            inputStream = (new BufferedHttpEntity(entity)).getContent();
            bmpImage = BitmapFactory.decodeStream(inputStream);
            //bmpImage = BitmapFactory.decodeStream(new URL(urlString).openConnection().getInputStream());
        }
        catch (Exception e)
        {
            Log.e("ImageDownloadError", e.toString());
            return;
        }
        if (bmpImage != null)
        {
            ImageHandler.addImage(bmpImage);
            Log.i("Info", "Image download successfully");
        }
        else
            Log.e("Error", "Bitmap is null");
    }
}

ps showImageButton拋出IllegalStateException ，但是我已經厭倦了它。

Answer 1

我認為問題在於，一旦您從HttpUrlConnection使用了InputStream，就無法后退並再次使用相同的InputStream。 因此，您必須為圖像的實際采樣創建一個新的InputStream。 否則，我們必須中止http請求。

只有當我們可以將inputstream用於httprequest時，如果您嘗試下載其他圖像，則它將像“已創建InputStream”那樣拋出錯誤。 因此，一旦使用httpRequest.abort（）下載后，我們需要中止httprequest。

用這個：

HttpGet httpRequest = new HttpGet(URI.create(path) );
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
HttpEntity entity = response.getEntity();
BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
bmp = BitmapFactory.decodeStream(bufHttpEntity.getContent());
httpRequest.abort();

Answer 2

根據我的觀點，有兩個原因

1. ImageHandler類無法獲取圖像
2. android給從源獲取gif圖像的問題。

我正在上傳一個有效的代碼，希望這可以解決您的問題。

主要活動

 public class MainActivity extends Activity {

    private ProgressDialog progressDialog;
    private ImageView imageView;
    private String url = "http://www.9ori.com/store/media/images/8ab579a656.jpg";
    private Bitmap bitmap = null;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

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

        Button start = (Button) findViewById(R.id.button1);
        start.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                progressDialog = ProgressDialog.show(MainActivity.this,
                        "", "Loading..");
                new Thread() {
                    public void run() {
                        bitmap = downloadBitmap(url);
                        messageHandler.sendEmptyMessage(0);
                    }
                }.start();

            }
        });
    }

    private Handler messageHandler = new Handler() {
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            imageView.setImageBitmap(bitmap);
            progressDialog.dismiss();
        }
    };

    private Bitmap downloadBitmap(String url) {
        // Initialize the default HTTP client object
        final DefaultHttpClient client = new DefaultHttpClient();

        //forming a HttoGet request
        final HttpGet getRequest = new HttpGet(url);
        try {

            HttpResponse response = client.execute(getRequest);

            //check 200 OK for success
            final int statusCode = response.getStatusLine().getStatusCode();

            if (statusCode != HttpStatus.SC_OK) {
                Log.w("ImageDownloader", "Error " + statusCode +
                        " while retrieving bitmap from " + url);
                return null;
            }

            final HttpEntity entity = response.getEntity();
            if (entity != null) {
                InputStream is = null;
                try {
                    // getting contents from the stream
                    is = entity.getContent();

                    // decoding stream data back into image Bitmap
                    final Bitmap bitmap = BitmapFactory.decodeStream(is);

                    return bitmap;
                } finally {
                    if (is != null) {
                        is.close();
                    }
                    entity.consumeContent();
                }
            }
        } catch (Exception e) {
            getRequest.abort();
            Log.e(getString(R.string.app_name), "Error "+ e.toString());
        }

        return null;
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_margin="15dp"
        android:text="Download Image" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:scaleType="centerInside"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

並且不要忘記在Manifest.xml文件中授予INTERNET權限