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"/>

源码下载

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