1. 导入依赖包
// retrofit, 基于okhttp，考虑到项目中经常会用到retrofit，就导入这个了。 compile 'com.squareup.retrofit2:retrofit:2.1.0' // butterknife compile 'com.jakewharton:butterknife:7.0.1' // rxjava 本例中线程切换要用到，代替handler compile 'io.reactivex:rxjava:1.1.6' compile 'io.reactivex:rxandroid:1.2.1'
2. 继承responsebody，生成带进度监听的progressresponsebody
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// 参考okhttp的官方demo，此类当中我们主要把注意力放在progresslistener和read方法中。在这里获取文件总长我写在了构造方法里，这样免得在source的read方法中重复调用或判断。读者也可以根据个人需要定制自己的监听器。
public class progressresponsebody extends responsebody {
public interface progresslistener {
void onpreexecute(long contentlength);
void update(long totalbytes, boolean done);
}
private final responsebody responsebody;
private final progresslistener progresslistener;
private bufferedsource bufferedsource;
public progressresponsebody(responsebody responsebody,
progresslistener progresslistener) {
this.responsebody = responsebody;
this.progresslistener = progresslistener;
if(progresslistener!=null){
progresslistener.onpreexecute(contentlength());
}
}
@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 totalbytes = 0l;
@override
public long read(buffer sink, long bytecount) throws ioexception {
long bytesread = super.read(sink, bytecount);
// read() returns the number of bytes read, or -1 if this source is exhausted.
totalbytes += bytesread != -1 ? bytesread : 0;
if (null != progresslistener) {
progresslistener.update(totalbytes, bytesread == -1);
}
return bytesread;
}
};
}
}
3.创建progressdownloader
//带进度监听功能的辅助类
public class progressdownloader {
public static final string tag = "progressdownloader";
private progresslistener progresslistener;
private string url;
private okhttpclient client;
private file destination;
private call call;
public progressdownloader(string url, file destination, progresslistener progresslistener) {
this.url = url;
this.destination = destination;
this.progresslistener = progresslistener;
//在下载、暂停后的继续下载中可复用同一个client对象
client = getprogressclient();
}
//每次下载需要新建新的call对象
private call newcall(long startpoints) {
request request = new request.builder()
.url(url)
.header("range", "bytes=" + startpoints + "-")//断点续传要用到的，指示下载的区间
.build();
return client.newcall(request);
}
public okhttpclient getprogressclient() {
// 拦截器，用上progressresponsebody
interceptor interceptor = new interceptor() {
@override
public response intercept(chain chain) throws ioexception {
response originalresponse = chain.proceed(chain.request());
return originalresponse.newbuilder()
.body(new progressresponsebody(originalresponse.body(), progresslistener))
.build();
}
};
return new okhttpclient.builder()
.addnetworkinterceptor(interceptor)
.build();
}
// startspoint指定开始下载的点
public void download(final long startspoint) {
call = newcall(startspoint);
call.enqueue(new callback() {
@override
public void onfailure(call call, ioexception e) {
}
@override
public void onresponse(call call, response response) throws ioexception {
save(response, startspoint);
}
});
}
public void pause() {
if(call!=null){
call.cancel();
}
}
private void save(response response, long startspoint) {
responsebody body = response.body();
inputstream in = body.bytestream();
filechannel channelout = null;
// 随机访问文件，可以指定断点续传的起始位置
randomaccessfile randomaccessfile = null;
try {
randomaccessfile = new randomaccessfile(destination, "rwd");
//chanel nio中的用法，由于randomaccessfile没有使用缓存策略，直接使用会使得下载速度变慢，亲测缓存下载3.3秒的文件，用普通的randomaccessfile需要20多秒。
channelout = randomaccessfile.getchannel();
// 内存映射，直接使用randomaccessfile，是用其seek方法指定下载的起始位置，使用缓存下载，在这里指定下载位置。
mappedbytebuffer mappedbuffer = channelout.map(filechannel.mapmode.read_write, startspoint, body.contentlength());
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
mappedbuffer.put(buffer, 0, len);
}
} catch (ioexception e) {
e.printstacktrace();
}finally {
try {
in.close();
if (channelout != null) {
channelout.close();
}
if (randomaccessfile != null) {
randomaccessfile.close();
}
} catch (ioexception e) {
e.printstacktrace();
}
}
}
}
4. 测试demo
清单文件中添加网络权限和文件访问权限
<uses-permission android:name="android.permission.internet"/> <uses-permission android:name="android.permission.write_external_storage"/>
mainactivity
public class mainactivity extends appcompatactivity implements progressresponsebody.progresslistener {
public static final string tag = "mainactivity";
public static final string package_url = "http://gdown.baidu.com/data/wisegame/df65a597122796a4/weixin_821.apk";
@bind(r.id.progressbar)
progressbar progressbar;
private long breakpoints;
private progressdownloader downloader;
private file file;
private long totalbytes;
private long contentlength;
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
butterknife.bind(this);
}
@onclick({r.id.downloadbutton, r.id.cancel_button, r.id.continue_button})
public void onclick(view view) {
switch (view.getid()) {
case r.id.downloadbutton:
// 新下载前清空断点信息
breakpoints = 0l;
file = new file(environment.getexternalstoragepublicdirectory(environment.directory_downloads), "sample.apk");
downloader = new progressdownloader(package_url, file, this);
downloader.download(0l);
break;
case r.id.pause_button:
downloader.pause();
toast.maketext(this, "下载暂停", toast.length_short).show();
// 存储此时的totalbytes，即断点位置。
breakpoints = totalbytes;
break;
case r.id.continue_button:
downloader.download(breakpoints);
break;
}
}
@override
public void onpreexecute(long contentlength) {
// 文件总长只需记录一次，要注意断点续传后的contentlength只是剩余部分的长度
if (this.contentlength == 0l) {
this.contentlength = contentlength;
progressbar.setmax((int) (contentlength / 1024));
}
}
@override
public void update(long totalbytes, boolean done) {
// 注意加上断点的长度
this.totalbytes = totalbytes + breakpoints;
progressbar.setprogress((int) (totalbytes + breakpoints) / 1024);
if (done) {
// 切换到主线程
observable
.empty()
.observeon(androidschedulers.mainthread())
.dooncompleted(new action0() {
@override
public void call() {
toast.maketext(mainactivity.this, "下载完成", toast.length_short).show();
}
})
.subscribe();
}
}
}
最后是动态效果图
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