看到这篇文章后面说会有大文件下载时会产生内存溢出的问题,还没验证,大家有处理过请留言
综述
在Retrofit2.0使用详解这篇文章中详细介绍了retrofit的用法。并且在retrofit中我们可以通过ResponseBody进行对文件的下载。但是在retrofit中并没有为我们提供显示下载进度的接口。在项目中,若是用户下载一个文件,无法实时给用户显示下载进度,这样用户的体验也是非常差的。那么下面就介绍一下在retrofit用于文件的下载如何实时跟踪下载进度。
演示
Retrofit文件下载进度更新的实现
在retrofit2.0中他依赖于Okhttp,所以如果我们需要解决这个问题还需要从这个OKhttp来入手。在Okhttp中有一个依赖包Okio。Okio也是有square公司所开发,它是Java.io和java.nio的补充,使用它更容易访问、存储和处理数据。在这里需要使用Okio中的Source类。在这里Source可以看做InputStream。对于Okio的详细使用在这里就不在介绍。下面来看一下具体实现。
在这里我们首先写一个接口,用于监听下载的进度。对于文件的下载,我们需要知道下载的进度,文件的总大小,以及是否操作完成。于是有了下面这样一个接口。
package com.ljd.retrofit.progress;/** * Created by ljd on 3/29/16. */public interface ProgressListener { /** * @param progress 已经下载或上传字节数 * @param total 总字节数 * @param done 是否完成 */ void onProgress(long progress, long total, boolean done);}
对于文件的下载我们需要重写ResponseBody类中的一些方法。
package com.ljd.retrofit.progress;import java.io.IOException;import okhttp3.MediaType;import okhttp3.ResponseBody;import okio.Buffer;import okio.BufferedSource;import okio.ForwardingSource;import okio.Okio;import okio.Source;/** * Created by ljd on 3/29/16. */public class ProgressResponseBody extends ResponseBody { private final ResponseBody responseBody; private final ProgressListener progressListener; private BufferedSource bufferedSource; public ProgressResponseBody(ResponseBody responseBody, ProgressListener progressListener) { this.responseBody = responseBody; this.progressListener = progressListener; } @Override public MediaType contentType() { return responseBody.contentType(); } @Override public long contentLength() { return responseBody.contentLength(); } @Override public BufferedSource source() { if (bufferedSource == null) { bufferedSource = Okio.buffer(source(responseBody.source())); } return bufferedSource; } private Source source(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; progressListener.onProgress(totalBytesRead, responseBody.contentLength(), bytesRead == -1); return bytesRead; } }; }}
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在上面ProgressResponseBody类中,我们计算已经读取文件的字节数,并且调用了ProgressListener接口。所以这个ProgressListener接口是在子线程中运行的。
下面就来看一下是如何使用这个ProgressResponseBody。
package com.ljd.retrofit.progress;import android.util.Log;import java.io.IOException;import okhttp3.Interceptor;import okhttp3.OkHttpClient;/** * Created by ljd on 4/12/16. */public class ProgressHelper { private static ProgressBean progressBean = new ProgressBean(); private static ProgressHandler mProgressHandler; public static OkHttpClient.Builder addProgress(OkHttpClient.Builder builder){ if (builder == null){ builder = new OkHttpClient.Builder(); } final ProgressListener progressListener = new ProgressListener() { @Override public void onProgress(long progress, long total, boolean done) { Log.d("progress:",String.format("%d%% done\n",(100 * progress) / total)); if (mProgressHandler == null){ return; } progressBean.setBytesRead(progress); progressBean.setContentLength(total); progressBean.setDone(done); mProgressHandler.sendMessage(progressBean); } }; builder.networkInterceptors().add(new Interceptor() { @Override public okhttp3.Response intercept(Chain chain) throws IOException { okhttp3.Response originalResponse = chain.proceed(chain.request()); return originalResponse.newBuilder().body( new ProgressResponseBody(originalResponse.body(), progressListener)) .build(); } }); return builder; } public static void setProgressHandler(ProgressHandler progressHandler){ mProgressHandler = progressHandler; }}
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我们通过为OkhttpClient添加一个拦截器来使用我们自定义的ProgressResponseBody。并且在这里我们可以通过实现ProgressListener接口。来获取下载进度了。但是在这里依然存在一个问题,刚才说到这个ProgressListener接口运行在子线程中。也就是说在ProgressListener这个接口中我们无法进行ui操作。而我们获取文件下载的进度往往则是需要一个进度条进行ui显示。显然这并不是我们想要的结果。
在这个时候我们就需要使用Handler了。我们可以通过Handler将子线程中的ProgressListener的数据发送到ui线程中进行处理。也就是说我们在ProgressListener接口中的操作只是将其参数通过Handler发送出去。很显然在上面的代码中我们通过ProgressHandler来发送消息。那么就来看一下具体操作。
这里我们创建一个对象,用于存放ProgressListener中的参数。
package com.example.ljd.retrofit.pojo;import java.util.ArrayList;import java.util.List;/** * Created by ljd on 3/29/16. */public class RetrofitBean { private Integer total_count; private Boolean incompleteResults; private List<Item> items = new ArrayList<Item>(); /** * * @return * The totalCount */ public Integer getTotalCount() { return total_count; } /** * * @param totalCount * The total_count */ public void setTotalCount(Integer totalCount) { this.total_count = totalCount; } /** * * @return * The incompleteResults */ public Boolean getIncompleteResults() { return incompleteResults; } /** * * @param incompleteResults * The incomplete_results */ public void setIncompleteResults(Boolean incompleteResults) { this.incompleteResults = incompleteResults; } /** * * @return * The items */ public List<Item> getItems() { return items; }}
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然后我们在创建一个ProgressHandler类。
package com.ljd.retrofit.progress;import android.os.Handler;import android.os.Looper;import android.os.Message;/** * Created by ljd on 4/12/16. */public abstract class ProgressHandler { protected abstract void sendMessage(ProgressBean progressBean); protected abstract void handleMessage(Message message); protected abstract void onProgress(long progress, long total, boolean done); protected static class ResponseHandler extends Handler{ private ProgressHandler mProgressHandler; public ResponseHandler(ProgressHandler mProgressHandler, Looper looper) { super(looper); this.mProgressHandler = mProgressHandler; } @Override public void handleMessage(Message msg) { mProgressHandler.handleMessage(msg); } }}
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上面的ProgressHandler他是一个抽象类。在这里我们需要通过Handler对象进行发送和处理消息。于是定义了两个抽象方法sendMessage和handleMessage。之后又定义了一个抽象方法onProgress来处理下载进度的显示,而这个onProgress则是我们需要在ui线程进行调用。最后创建了一个继承自Handler的ResponseHandler内部类。为了避免内存泄露我们使用static关键字。
下面来创建一个DownloadProgressHandler类,他继承于ProgressHandler,用来发送和处理消息。
package com.ljd.retrofit.progress;import android.os.Looper;import android.os.Message;/** * Created by ljd on 4/12/16. */public abstract class DownloadProgressHandler extends ProgressHandler{ private static final int DOWNLOAD_PROGRESS = 1; protected ResponseHandler mHandler = new ResponseHandler(this, Looper.getMainLooper()); @Override protected void sendMessage(ProgressBean progressBean) { mHandler.obtainMessage(DOWNLOAD_PROGRESS,progressBean).sendToTarget(); } @Override protected void handleMessage(Message message){ switch (message.what){ case DOWNLOAD_PROGRESS: ProgressBean progressBean = (ProgressBean)message.obj; onProgress(progressBean.getBytesRead(),progressBean.getContentLength(),progressBean.isDone()); } }}
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在这里我们接收到消息以后调用抽象方法onProgress,这样一来我们只需要创建一个DownloadProgressHandler对象,实现onProgress即可。
对于上面的分析,下面我们就来看一下是如何使用的。
package com.example.ljd.retrofit.downloadimport android.app.ProgressDialogimport android.os.Environmentimport android.os.Looperimport android.support.v7.app.AppCompatActivityimport android.os.Bundleimport android.util.Logimport com.example.ljd.retrofit.Rimport com.ljd.retrofit.progress.DownloadProgressHandlerimport com.ljd.retrofit.progress.ProgressHelperimport java.io.BufferedInputStreamimport java.io.Fileimport java.io.FileOutputStreamimport java.io.IOExceptionimport java.io.InputStreamimport butterknife.ButterKnifeimport butterknife.OnClickimport okhttp3.OkHttpClientimport okhttp3.ResponseBodyimport retrofit2.Callimport retrofit2.Callbackimport retrofit2.Responseimport retrofit2.Retrofitimport retrofit2.adapter.rxjava.RxJavaCallAdapterFactoryimport retrofit2.converter.gson.GsonConverterFactorypublic class DownloadActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_download) ButterKnife.bind(this) } @Override protected void onDestroy() { ButterKnife.unbind(this) super.onDestroy() } @OnClick(R.id.start_download_btn) public void onClickButton(){ retrofitDownload() } private void retrofitDownload(){ //监听下载进度 final ProgressDialog dialog = new ProgressDialog(this) dialog.setProgressNumberFormat("%1d KB/%2d KB") dialog.setTitle("下载") dialog.setMessage("正在下载,请稍后...") dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL) dialog.setCancelable(false) dialog.show() Retrofit.Builder retrofitBuilder = new Retrofit.Builder() .addCallAdapterFactory(RxJavaCallAdapterFactory.create()) .addConverterFactory(GsonConverterFactory.create()) .baseUrl("http://msoftdl.360.cn") OkHttpClient.Builder builder = ProgressHelper.addProgress(null) DownloadApi retrofit = retrofitBuilder .client(builder.build()) .build().create(DownloadApi.class) ProgressHelper.setProgressHandler(new DownloadProgressHandler() { @Override protected void onProgress(long bytesRead, long contentLength, boolean done) { Log.e("是否在主线程中运行", String.valueOf(Looper.getMainLooper() == Looper.myLooper())) Log.e("onProgress",String.format("%d%% done\n",(100 * bytesRead) / contentLength)) Log.e("done","--->" + String.valueOf(done)) dialog.setMax((int) (contentLength/1024)) dialog.setProgress((int) (bytesRead/1024)) if(done){ dialog.dismiss() } } }) Call<ResponseBody> call = retrofit.retrofitDownload() call.enqueue(new Callback<ResponseBody>() { @Override public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) { try { InputStream is = response.body().byteStream() File file = new File(Environment.getExternalStorageDirectory(), "12345.apk") FileOutputStream fos = new FileOutputStream(file) BufferedInputStream bis = new BufferedInputStream(is) byte[] buffer = new byte[1024] int len while ((len = bis.read(buffer)) != -1) { fos.write(buffer, 0, len) fos.flush() } fos.close() bis.close() is.close() } catch (IOException e) { e.printStackTrace() } } @Override public void onFailure(Call<ResponseBody> call, Throwable t) { } }) }}
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总结
对于上面的实现我们可以看出是通过OkhttpClient实现的。也正是由于在retrofit2.0中它依赖于OkHttp,因此对于OkHttp的功能retrofit也都具备。利用这一特性,我们可以通过定制OkhttpClient来配置我们的retrofit。
源码下载