OkHttp下载文件并带进度条

做这一行，不能太懒，不然就被淘汰！

OkHttp是比较火的网络框架，它支持同步与异步请求，支持缓存，可以拦截，更方便下载大文件与上传文件的操作。下面我们用OkHttp来下载文件并带进度条！

相关资料：
官网地址：http://square.github.io/okhttp/

github源码地址：https://github.com/square/okhttp

一、服务器端简单搭建

可以参考搭建本地Tomcat服务器及相关配置 这篇文章。

新建项目OkHttpServer，在WebContent目录下新建downloadfile目录，将要下载的jpg文件放在项目下。如下图：

启动服务器，文件下载地址为http://localhost:8080/OkHttpServer/download/2.jpg 。这样我们服务器就搭好了。

二、Android端

下面我们进入正题。

1.build.gradle的dependencies配置如下

 compile 'com.android.support:appcompat-v7:24.1.1'compile 'com.squareup.okhttp3:okhttp:3.2.0'compile 'com.squareup.okio:okio:1.7.0'

2.activity_main.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.huang.myokhttp.MainActivity">    <Button        android:id="@+id/ok_download"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="下载文件" />    <TextView        android:id="@+id/download_text"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center"        android:text="0" />    <ProgressBar        android:id="@+id/download_progress"        style="?android:attr/progressBarStyleHorizontal"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:max="100" /></RelativeLayout>

3.编写OkHttpUtil如下：

  private static OkHttpClient okHttpClient = new OkHttpClient.Builder().connectTimeout(10000, TimeUnit.MILLISECONDS)                                                .readTimeout(10000,TimeUnit.MILLISECONDS)                                                .writeTimeout(10000,TimeUnit.MILLISECONDS).build();    //下载文件方法    public static void downloadFile(String url, final ProgressListener listener, Callback callback){    //增加拦截器        OkHttpClient client = okHttpClient.newBuilder().addNetworkInterceptor(new Interceptor() {            @Override            public Response intercept(Chain chain) throws IOException {                Response response = chain.proceed(chain.request());                return response.newBuilder().body(new ProgressResponseBody(response.body(),listener)).build();            }        }).build();        Request request  = new Request.Builder().url(url).build();        client.newCall(request).enqueue(callback);    }

4.上面代码中的ProgressResponseBody是自己编写的类，ProgressListener 是监听的接口：
ProgressListener 接口

public interface ProgressListener {//已完成的 总的文件长度 是否完成    void onProgress(long currentBytes, long contentLength, boolean done);}

ProgressResponseBody继承ResponseBody ，返回监听进度

public class ProgressResponseBody extends ResponseBody {    public static final int UPDATE = 0x01;    public static final String TAG = ProgressResponseBody.class.getName();    private ResponseBody responseBody;    private ProgressListener mListener;    private BufferedSource bufferedSource;    private Handler myHandler;    public ProgressResponseBody(ResponseBody body, ProgressListener listener) {        responseBody = body;        mListener = listener;        if (myHandler==null){            myHandler = new MyHandler();        }    }    /**     * 将进度放到主线程中显示     */    class MyHandler extends Handler {        public MyHandler() {            super(Looper.getMainLooper());        }        @Override        public void handleMessage(Message msg) {            switch (msg.what){                case UPDATE:                    ProgressModel progressModel = (ProgressModel) msg.obj;                    //接口返回                    if (mListener!=null)mListener.onProgress(progressModel.getCurrentBytes(),progressModel.getContentLength(),progressModel.isDone());                    break;            }        }    }    @Override    public MediaType contentType() {        return responseBody.contentType();    }    @Override    public long contentLength() {        return responseBody.contentLength();    }    @Override    public BufferedSource source() {        if (bufferedSource==null){            bufferedSource = Okio.buffer(mySource(responseBody.source()));        }        return bufferedSource;    }    private Source mySource(Source source) {        return  new ForwardingSource(source) {            long totalBytesRead = 0L;            @Override            public long read(Buffer sink, long byteCount) throws IOException {                long bytesRead = super.read(sink, byteCount);                totalBytesRead +=bytesRead!=-1?bytesRead:0;                //发送消息到主线程，ProgressModel为自定义实体类                Message msg = Message.obtain();                msg.what = UPDATE;                msg.obj =  new ProgressModel(totalBytesRead,contentLength(),totalBytesRead==contentLength());                myHandler.sendMessage(msg);                return bytesRead;            }        };    }}

5.MainActivity的代码：

public class MainActivity extends AppCompatActivity implements View.OnClickListener{    public static final String TAG = MainActivity.class.getName();    private ProgressBar download_progress;    private TextView download_text;    public static String basePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/okhttp";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        download_progress = (ProgressBar) findViewById(R.id.download_progress);        download_text = (TextView) findViewById(R.id.download_text);        findViewById(R.id.ok_download).setOnClickListener(this);    }    @Override    public void onClick(View view) {        switch (view.getId()){            case R.id.ok_download:                String url = "http://192.168.0.104:8080/OkHttpServer/download/2.jpg";                final String fileName = url.split("/")[url.split("/").length - 1];                Log.i(TAG, "fileName==" + fileName);                OkHttpUtil.downloadFile(url, new ProgressListener() {                    @Override                    public void onProgress(long currentBytes, long contentLength, boolean done) {                        Log.i(TAG, "currentBytes==" + currentBytes + "==contentLength==" + contentLength + "==done==" + done);                        int progress = (int) (currentBytes * 100 / contentLength);                        download_progress.setProgress(progress);                        download_text.setText(progress + "%");                    }                }, new Callback() {                    @Override                    public void onFailure(Call call, IOException e) {                    }                    @Override                    public void onResponse(Call call, Response response) throws IOException {                        if (response != null) {                            InputStream is = response.body().byteStream();                            FileOutputStream fos = new FileOutputStream(new File(basePath + "/" + fileName));                            int len = 0;                            byte[] buffer = new byte[2048];                            while (-1 != (len = is.read(buffer))) {                                fos.write(buffer, 0, len);                            }                            fos.flush();                            fos.close();                            is.close();                        }                    }                });                break;        }    }}

6.最后不要忘了添加权限：

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

下载文件目录结构

源码下载