Android 中的位图回收 - 何时何地？

Question

我不确定如何回收位图。

我有一个在列表视图中显示大量项目的应用程序。问题是如果我不降低 ImageDownloader 类中图像的质量，应用程序就会崩溃。

在下面提供的代码中，如果我更改 options.inSampleSize = 4，图像质量会降低，并且应用程序不会耗尽内存。但是，我想使用高质量的图像而不会使我的应用程序崩溃。

我该怎么做？

我的 ImageDownloader 的一部分：

static Bitmap downloadBitmap(String url) {
    HttpParams params = new BasicHttpParams();
    params.setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);
    HttpClient client = new DefaultHttpClient(params);
    final HttpGet getRequest = new HttpGet(url);

    try {
        HttpResponse response = client.execute(getRequest);
        final int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode != HttpStatus.SC_OK) {
            String[] urlBits = url.split("/");
            Bitmap bitmap = MiscHelpers.getBitmapFromAsset(context, "animals/" + urlBits[urlBits.length-2] + ".jpg");
            Log.w("ImageDownloader", "Error " + statusCode + " while retrieving bitmap from " + url);
            return bitmap;
        }

        final HttpEntity entity = response.getEntity();
        if (entity != null) {
            InputStream inputStream = null;
            try {
                inputStream = entity.getContent();
                BitmapFactory.Options options=new BitmapFactory.Options();
                options.inSampleSize = 1;


                final Bitmap bitmap = BitmapFactory.decodeStream(inputStream,null,options);
                //final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);

                return bitmap;
            } finally {
                if (inputStream != null) {
                    inputStream.close();  
                }
                entity.consumeContent();
            }
        }
    } catch (Exception e) {
        // Could provide a more explicit error message for IOException or IllegalStateException
        getRequest.abort();
        Log.w("ImageDownloader", "Error while retrieving bitmap from " + url + e.toString());
    } finally {
        if (client != null) {
            //client.close();
        }
    }
    return null;
}

我的 ListView 适配器：

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    // Inflate the layout
    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View rowView = inflater.inflate(R.layout.list_single, parent, false);

    ImageView image = (ImageView) rowView.findViewById(R.id.picture);
    TextView firstline = (TextView) rowView.findViewById(R.id.firstline);
    TextView secondline = (TextView) rowView.findViewById(R.id.secondline);         

    // Get information about the report
    AnimalLocationLog current = objects.get(position);

    // Get all the important information
    String species = current.getSpecies();
    String sanitizedSpecies = MiscHelpers.sanitizeString(species);
    int reportId = objects.get(position).getTrackerId();

    // Construct the URL to the image
    String imageLocation = websiteUrl + sanitizedSpecies + separator + reportId + extension;

    // Display user report          
    downloader.download(imageLocation, image);          
    firstline.setText(species);
    secondline.setText("Spotted " + current.getDateTime().toString("yyyy-MM-dd H:m"));          

    urlToPath = downloader.getUrlToPath();

    return rowView;
}

Answer 1

我看不出有什么明显的错误。也许在图像编辑方面可以做一些事情来使图像更小？

我建议进行堆转储并将其加载到 Eclipse MAT，https://www.eclipse.org/mat/，以全面了解正在发生的事情。我特别推荐查看 Dominators 报告。