在android中，目前主流的加载图片基本都是用Glide框架。这个框架会自动的为我们处理网络加载与缓存图片的各种功能，而我们只需要给图片的地址与显示位置即可。但在加载图片的过程中我们无法知道当前加载的进度，所以我们需要对Glide进行扩展。
同理，我们先来看看效果：

现在我们正式开始吧

添加依赖

implementation 'com.github.bumptech.glide:glide:3.7.0'
implementation 'com.squareup.okhttp3:okhttp:3.9.0'

添加权限

<uses-permission android:name="android.permission.INTERNET" />

替换Glide里面网络通讯组件HTTP为OkHttp。
新建一个OkHttpFetcher类，并且实现DataFetcher接口，代码如下所示：

package cn.xie.fingerprinttest.http;

import com.bumptech.glide.Priority;
import com.bumptech.glide.load.data.DataFetcher;
import com.bumptech.glide.load.model.GlideUrl;
import com.bumptech.glide.util.ContentLengthInputStream;

import java.io.IOException;
import java.io.InputStream;
import java.util.Map;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;

/**
 * 将Glide中的HTTP通讯组件替换成OkHttp。
 * @author xiejinbo
 * @date 2019/11/12 0012 11:43
 */
public class OkHttpFetcher implements DataFetcher<InputStream> {
   

        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<String, String> headerEntry : url.getHeaders().entrySet()) {
   
                String key = headerEntry.getKey();
                requestBuilder.addHeader(key, 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