android中实现OkHttp下载文件并带进度条

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 *
   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"/>

源码下载

来源：http://blog.csdn.net/Gary__123456/article/details/74157403