Glide自定义模块详解

创建自定义模块类：首先需要定义一个自定义模块类，并实现GlideModule接口。例如：

public class MyGlideModule implements GlideModule {
    @Override
    public void applyOptions(Context context, GlideBuilder builder) {
        // 在这里添加Glide配置
    }
    @Override
    public void registerComponents(Context context, Glide glide) {
        // 在这里替换或添加Glide组件
    }
}

注册自定义模块：在AndroidManifest.xml中添加以下配置：

配置和替换：在applyOptions中初始化配置，在registerComponents中替换或添加组件。

public class MyGlideModule implements GlideModule {
    @Override
    public void applyOptions(Context context, GlideBuilder builder) {
        builder.setDiskCache(new ExternalCacheDiskCacheFactory(context));
    }
    @Override
    public void registerComponents(Context context, Glide glide) {
        glide.register(GlideUrl.class, InputStream.class, new OkHttpGlideUrlLoader.Factory());
    }
}

Glide的单例结构：Glide采用双重锁机制保证只有一个Glide实例。这一实例负责解析AndroidManifest.xml中的Glide模块配置，并初始化相关组件。

模块化配置：通过GlideBuilder，在applyOptions中可以设置内存缓存、硬盘缓存等配置。这些配置会影响Glide的默认行为。

组件替换：registerComponents允许替换Glide的默认组件。例如，通过注册自定义的GlideUrlLoader，实现对Glide网络通信逻辑的自定义。

implements ModelLoader和DataFetcher接口：

public class OkHttpGlideUrlLoader implements ModelLoader
    
      {
    private OkHttpClient okHttpClient;
    public static class Factory implements ModelLoaderFactory
     
       {
        private OkHttpClient client;
        public Factory() {}
        public Factory(OkHttpClient client) {
            this.client = client;
        }
        @Override
        public ModelLoader
      
        build(
                Context context, GenericLoaderFactory factories) {
            return new OkHttpGlideUrlLoader(getOkHttpClient());
        }
        @Override
        public void teardown() {}
    }
    public OkHttpGlideUrlLoader(OkHttpClient client) {
        this.okHttpClient = client;
    }
    @Override
    public DataFetcher
       
         getResourceFetcher(
            GlideUrl model, int width, int height) {
        return new OkHttpFetcher(okHttpClient, model);
    }
}
public class OkHttpFetcher implements DataFetcher
        
          {
    private final OkHttpClient client;
    private final GlideUrl url;
    private InputStream stream;
    public OkHttpFetcher(OkHttpClient client, GlideUrl url) {
        this.client = client;
        this.url = url;
    }
    @Override
    public InputStream loadData(Priority priority) throws Exception {
        Request request = new Request.Builder()
                .url(url.toStringUrl())
                .addHeader("httplib", "OkHttp")
                .addHeaders(url.getHeaders())
                .build();
        Response response = client.newCall(request).execute();
        if (!response.isSuccessful()) {
            throw new IOException("Request failed: " + response.code());
        }
        InputStream stream = getContentStream(response);
        return stream;
    }
    private InputStream getContentStream(HttpURLConnection response) {
        if (response.getContentEncoding() != null) {
            return new ContentLengthInputStream(response.getInputStream(),
                    response.getContentLength());
        } else {
            return response.getInputStream();
        }
    }
    @Override
    public void cleanup() {
        try {
            if (stream != null) {
                stream.close();
            }
            if (response != null) {
                response.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public String getId() {
        return url.getCacheKey();
    }
    @Override
    public void cancel() {
        // 通过OkHttp的interceptor进行资源管理
    }
}