Android加载自动下载型URL图片遇阻：Picasso/Glide无法处理该类链接

我之前也踩过一模一样的坑！这种自动触发下载的URL，核心问题是服务器返回的响应头里带了Content-Disposition: attachment，而Picasso和Glide默认会把这类响应当成“需要下载的文件”，而非直接可展示的图片资源（正常图片响应头一般是Content-Disposition: inline），所以才会加载失败。

下面给你两种库的具体解决办法：

针对Picasso的解决方案 #

你需要自定义一个OkHttpDownloader，拦截响应并强制处理成可展示的图片：

public class CustomPicassoDownloader extends OkHttp3Downloader {
    public CustomPicassoDownloader(Context context) {
        super(context);
    }

    public CustomPicassoDownloader(OkHttpClient client) {
        super(client);
    }

    @Override
    public Response load(Uri uri, int networkPolicy) throws IOException {
        Response originalResponse = super.load(uri, networkPolicy);
        // 忽略Content-Disposition的attachment标记，强制返回图片流
        return originalResponse.newBuilder()
                .header("Content-Disposition", "inline")
                .build();
    }
}

然后在初始化Picasso的时候替换默认下载器：

OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
Picasso picasso = new Picasso.Builder(context)
        .downloader(new CustomPicassoDownloader(okHttpClient))
        .build();
Picasso.setSingletonInstance(picasso);

之后再用Picasso加载目标链接就正常了。

针对Glide的解决方案 #

Glide可以通过自定义OkHttpUrlLoader来处理这类响应：

首先创建一个自定义的OkHttpStreamFetcher，修改响应处理逻辑：

public class CustomOkHttpStreamFetcher implements DataFetcher<InputStream> {
    private final OkHttpClient client;
    private final GlideUrl url;
    private InputStream stream;
    private Response response;

    public CustomOkHttpStreamFetcher(OkHttpClient client, GlideUrl url) {
        this.client = client;
        this.url = url;
    }

    @Override
    public void loadData(Priority priority, DataCallback<? super InputStream> callback) {
        Request.Builder requestBuilder = new Request.Builder().url(url.toStringUrl());
        for (Map.Entry<String, String> headerEntry : url.getHeaders().entrySet()) {
            String key = headerEntry.getKey();
            requestBuilder.addHeader(key, headerEntry.getValue());
        }

        Request request = requestBuilder.build();
        try {
            response = client.newCall(request).execute();
            // 强制把attachment改成inline，让Glide识别为可展示的图片
            Response modifiedResponse = response.newBuilder()
                    .header("Content-Disposition", "inline")
                    .build();
            stream = modifiedResponse.body().byteStream();
            callback.onDataReady(stream);
        } catch (IOException e) {
            callback.onLoadFailed(e);
        }
    }

    @Override
    public void cleanup() {
        try {
            if (stream != null) {
                stream.close();
            }
            if (response != null) {
                response.body().close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void cancel() {}

    @Override
    public Class<InputStream> getDataClass() {
        return InputStream.class;
    }

    @Override
    public DataSource getDataSource() {
        return DataSource.REMOTE;
    }
}

然后创建自定义的OkHttpUrlLoader：

public class CustomOkHttpUrlLoader implements ModelLoader<GlideUrl, InputStream> {
    private final OkHttpClient client;

    public CustomOkHttpUrlLoader(OkHttpClient client) {
        this.client = client;
    }

    @Override
    public LoadData<InputStream> buildLoadData(GlideUrl model, int width, int height, Options options) {
        return new LoadData<>(new ObjectKey(model), new CustomOkHttpStreamFetcher(client, model));
    }

    @Override
    public boolean handles(GlideUrl model) {
        return true;
    }

    public static class Factory implements ModelLoaderFactory<GlideUrl, InputStream> {
        private static volatile OkHttpClient internalClient;
        private final OkHttpClient client;

        public Factory() {
            this(getInternalClient());
        }

        public Factory(OkHttpClient client) {
            this.client = client;
        }

        private static OkHttpClient getInternalClient() {
            if (internalClient == null) {
                synchronized (Factory.class) {
                    if (internalClient == null) {
                        internalClient = new OkHttpClient.Builder().build();
                    }
                }
            }
            return internalClient;
        }

        @Override
        public ModelLoader<GlideUrl, InputStream> build(MultiModelLoaderFactory multiFactory) {
            return new CustomOkHttpUrlLoader(client);
        }

        @Override
        public void teardown() {}
    }
}

最后在Glide的配置类里注册这个Loader：

@GlideModule
public class MyGlideModule extends AppGlideModule {
    @Override
    public void registerComponents(Context context, Glide glide, Registry registry) {
        OkHttpClient client = new OkHttpClient.Builder().build();
        registry.replace(GlideUrl.class, InputStream.class, new CustomOkHttpUrlLoader.Factory(client));
    }
}

这样配置后Glide就能正常加载这类自动下载的图片链接了。

本质上就是通过修改响应头，让图片库认为这是一个可以直接展示的内嵌资源，而不是需要下载的附件。

内容的提问来源于stack exchange，提问作者George Radu