Glide源码学习八：实现带进度的Glide图片加载功能-白红宇的个人博客

Glide源码学习八：实现带进度的Glide图片加载功能

发布日期：2021-05-14 18:09:50 浏览次数：18 分类：精选文章

本文共 9631 字，大约阅读时间需要 32 分钟。

如何在Glide中实现下载进度监听功能

一、项目准备工作

创建新项目

创建一个名为 GlideProgressTest 的新项目，用于测试Glide的自定义下载进度功能。

添加依赖库

在 app/build.gradle 中添加必要的组件依赖：

dependencies {
    compile 'com.github.bumptech.glide:glide:3.7.0'
    compile 'com.squareup.okhttp3:okhttp:3.9.0'
}

网络权限声明

在 AndroidManifest.xml 文件中添加网络权限：

二、替换Glide的HTTP通讯组件到OkHttp

创建自定义OkHttpFetcher类

这个类实现 DataFetcher 接口，用于处理HTTP请求：

public class OkHttpFetcher implements DataFetcher
    
      {
    private final OkHttpClient client;
    private final GlideUrl url;
    private InputStream stream;
    private ResponseBody responseBody;
    private volatile boolean isCancelled;
    public OkHttpFetcher(OkHttpClient client, GlideUrl url) {
        this.client = client;
        this.url = url;
    }
    @Override
    public InputStream loadData(Priority priority) throws Exception {
        Request.Builder requestBuilder = new Request.Builder()
            .url(url.toStringUrl());
        for (Map.Entry
     
       headerEntry : url.getHeaders().entrySet()) {
            requestBuilder.addHeader(headerEntry.getKey(), headerEntry.getValue());
        }
        Request request = requestBuilder.build();
        if (isCancelled) {
            return null;
        }
        Response response = client.newCall(request).execute();
        responseBody = response.body();
        if (!response.isSuccessful() || responseBody == null) {
            throw new IOException("Request failed with code: " + response.code());
        }
        stream = ContentLengthInputStream.obtain(
            responseBody.byteStream(),
            responseBody.contentLength());
        return stream;
    }
    @Override
    public void cleanup() {
        try {
            if (stream != null) {
                stream.close();
            }
            if (responseBody != null) {
                responseBody.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public String getId() {
        return url.getCacheKey();
    }
    @override
    public void cancel() {
        isCancelled = true;
    }
}

创建OkHttpGlideUrlLoader类

该类实现 ModelLoader 接口，用于加载数据：

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 fyFactory) {
            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);
    }
}

注册组件到Glide中

在 MyGlideModule 类中注册自定义组件：

public class MyGlideModule implements GlideModule {
    @Override
    public void applyOptions(Context context, GlideBuilder builder) {}
    @Override
    public void registerComponents(Context context, Glide glide) {
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.addInterceptor(new ProgressInterceptor());
        OkHttpClient okHttpClient = builder.build();
        glide.register(
            GlideUrl.class,
            Inputstream.class,
            new OkHttpGlideUrlLoader.Factory(okHttpClient));
    }
}

声明Glide模块

在 AndroidManifest.xml 中添加模块声明：

三、实现下载进度监听

创建ProgressInterceptor拦截器类

该类实现 Interceptor 接口，用于拦截HTTP请求并处理进度信息：

public class ProgressInterceptor implements Interceptor {
    private static final Map
    
      LISTENER_MAP = new HashMap<>();
    public static void addListener(String url, ProgressListener listener) {
        LISTENER_MAP.put(url, listener);
    }
    public static void removeListener(String url) {
        LISTENER_MAP.remove(url);
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        Response response = chain.proceed(request);
        String url = request.url().toString();
        ResponseBody body = response.body();
        Response newResponse = response
            .newBuilder()
            .body(new ProgressResponseBody(url, body))
            .build();
        return newResponse;
    }
}

创建ProgressResponseBody类

该类继承 ResponseBody，用于处理下载流并计算进度：

public class ProgressResponseBody extends ResponseBody {
    private static final String TAG = "ProgressResponseBody";
    private BufferedSource bufferedSource;
    private ProgressListener listener;
    private ResponseBody responseBody;
    public ProgressResponseBody(String url, ResponseBody responseBody) {
        this.responseBody = responseBody;
        listener = ProgressInterceptor.LISTENER_MAP.get(url);
    }
    @Override
    public MediaType contentType() {
        return responseBody.contentType();
    }
    @override
    public long contentLength() {
        return responseBody.contentLength();
    }
    @override
    public BufferedSource source() {
        if (bufferedSource == null) {
            bufferedSource = Okio.buffer(new ProgressSource(responseBody.source()));
        }
        return bufferedSource;
    }
    private class ProgressSource extends ForwardingSource {
        private long totalBytesRead;
        private int currentProgress;
        ProgressSource(Source source) {
            super(source);
        }
        @Override
        public long read(Buffer sink, long byteCount) throws IOException {
            long bytesRead = super.read(sink, byteCount);
            long fullLength = responseBody.contentLength();
            if (bytesRead == -1) {
                totalBytesRead = fullLength;
            } else {
                totalBytesRead += bytesRead;
            }
            int progress = (int) (100f * totalBytesRead / fullLength);
            Log.d(TAG, "download progress is " + progress);
            boolean hasChanged = progress != currentProgress;
            currentProgress = progress;
            if (listener != null && hasChanged) {
                listener.onProgress(progress);
            }
            return bytesRead;
        }
    }
}

在Glide中启用拦截器

修改 MyGlideModule 类，使其在注册组件时启用OkHttp客户端和拦截器：

public class MyGlideModule implements GlideModule {
    @Override
    public void applyOptions(Context context, GlideBuilder builder) {}
    @Override
    public void registerComponents(Context context, Glide glide) {
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.addInterceptor(new ProgressInterceptor());
        OkHttpClient okHttpClient = builder.build();
        glide.register(
            GlideUrl.class,
            Inputstream.class,
            new OkHttpGlideUrlLoader.Factory(okHttpClient));
    }
}

四、集成进度显示到用户界面

在MainActivity中创建ProgressDialog

在 MainActivity 中定义并初始化一个进度条：

public class MainActivity extends AppCompatActivity {
    String url = "http://guolin.tech/book.png";
    ImageView image;
    ProgressDialog progressDialog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        image = (ImageView) findViewById(R.id.image);
        progressDialog = new ProgressDialog(this);
        progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressDialog.setMessage("加载中");
    }
    public void loadImage(View view) {
        ProgressInterceptor.addListener(url, new ProgressListener() {
            @Override
            public void onProgress(int progress) {
                progressDialog.setProgress(progress);
            }
        });
        Glide.with(this)
             .load(url)
             .diskCacheStrategy(DiskCacheStrategy.NONE)
             .override(Target.SIZE_ORIGINAL, Target.SIZE_ORIGINAL)
             .into(new GlideDrawableImageViewTarget(image) {
                 @Override
                 public void onLoadStarted(Drawable placeholder) {
                     super.onLoadStarted(placeholder);
                     progressDialog.show();
                 }
                 @Override
                 public void onResourceReady(GlideDrawable resource, GlideAnimation animation) {
                     super.onResourceReady(resource, animation);
                     progressDialog.dismiss();
                     ProgressInterceptor.removeListener(url);
                 }
             });
    }
}

在GlideDrawableImageViewTarget中添加进度显示逻辑

确保在图片加载开始和完成时更新进度条：

class GlideDrawableImageViewTarget extends GlideDrawableImageViewTarget {
    GlideDrawableImageViewTarget(ImageView view) {
        super(view);
    }
    @Override
    public void onLoadStarted(Drawable placeholder) {
        super.onLoadStarted(placeholder);
        progressDialog.show();
    }
    @override
    public void onResourceReady(GlideDrawable resource, GlideAnimation animation) {
        super.onResourceReady(resource, animation);
        progressDialog.dismiss();
        ProgressInterceptor.removeListener(url);
    }
}

五、测试与验证

运行应用程序

在 Android Studio 中运行应用程序，点击 Load Image 按钮加载图片。

观察清单

通过 logcat 工具观察下载进度信息，确保进度监听功能正常工作。

测试不同图片类型

尝试加载不同大小和类型的图片（如GIF图），验证进度计算和显示的准确性。

优化UI布局

为进度条添加更多自定义样式，如颜色、动画效果，以提升用户体验。

六、总结

通过以上步骤，我们成功实现了Glide的下载进度监听功能。关键点包括替换Glide的HTTP通讯组件为OkHttp，利用OkHttp的强大拦截器机制实现进度监听，并通过自定义组件集成进度显示到用户界面。这种方法确保了下载进度能够实时反馈给用户，提升用户体验。

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