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本文实例为大家分享了android实现断点续传和下载的具体代码，供大家参考，具体内容如下
效果展示
导入依赖与权限
依赖
compile 'com.loopj.android:android-async-http:1.4.9'
权限
<uses-permission android:name="android.permission.internet"></uses-permission> <uses-permission android:name="android.permission.write_external_storage"></uses-permission> <uses-permission android:name="android.permission.read_external_storage"></uses-permission>
主mainactivity（布局）
<?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:id="@+id/activity_main" 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.lv.mama.test004.mainactivity"> <progressbar style="?android:attr/progressbarstylehorizontal" android:layout_width="match_parent" android:layout_height="20dp" android:layout_margintop="15dp" android:id="@+id/pb" android:layout_alignparenttop="true" android:layout_alignparentleft="true" android:layout_alignparentstart="true" /> <textview android:text="textview" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/pb" android:layout_alignparentleft="true" android:layout_alignparentstart="true" android:layout_marginleft="20dp" android:layout_marginstart="20dp" android:layout_margintop="13dp" android:id="@+id/tv_info" /> <button android:text="暂停" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_margintop="17dp" android:id="@+id/bt_pause" android:onclick="pause" android:layout_below="@+id/tv_info" android:layout_alignparentleft="true" android:layout_alignparentstart="true" android:layout_marginleft="11dp" android:layout_marginstart="11dp" /> <button android:text="开始" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginright="24dp" android:layout_marginend="24dp" android:id="@+id/bt_download" android:onclick="download" android:layout_alignbaseline="@+id/bt_pause" android:layout_alignbottom="@+id/bt_pause" android:layout_alignparentright="true" android:layout_alignparentend="true" /> </relativelayout>
主mainactivity
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public class mainactivity extends appcompatactivity {
protected static final string tag = "otheractivity";
//下载线程的数量
private final static int threadsize = 3;
protected static final int set_max = 0;
public static final int update_view = 1;
private progressbar pb;
private button bt_download;
private button bt_pause;
private textview tv_info;
//显示进度和更新进度
private handler mhandler = new handler() {
public void handlemessage(android.os.message msg) {
switch (msg.what) {
case set_max://设置进度条的最大值
int filelength = msg.arg1;
pb.setmax(filelength);
break;
case update_view://更新进度条 和 下载的比率
int len = msg.arg1;//新下载的长度
pb.setprogress(pb.getprogress() + len);//设置进度条的刻度
int max = pb.getmax();//获取进度的最大值
int progress = pb.getprogress();//获取已经下载的数据量
// 下载：30 总：100
int result = (progress * 100) / max;
tv_info.settext("下载:" + result + "%");
break;
default:
break;
}
}
;
};
string uri = "http://c.hiphotos.baidu.com/image/pic/item/b90e7bec54e736d1e51217c292504fc2d46269f3.jpg";
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
//找到控件
pb = (progressbar) findviewbyid(r.id.pb);
tv_info = (textview) findviewbyid(r.id.tv_info);
bt_download = (button) findviewbyid(r.id.bt_download);
bt_pause = (button) findviewbyid(r.id.bt_pause);
//数据的回显
//确定下载的文件
string name = getfilename(uri);
file file = new file(environment.getexternalstoragedirectory(), name);
if (file.exists()) {//文件存在回显
//获取文件的大小
int filelength = (int) file.length();
pb.setmax(filelength);
try {
//统计原来所有的下载量
int count = 0;
//读取下载记录文件
for (int threadid = 0; threadid < threadsize; threadid++) {
//获取原来指定线程的下载记录
int existdownloadlength = readdownloadinfo(threadid);
count = count + existdownloadlength;
}
//设置进度条的刻度
pb.setprogress(count);
//计算比率
int result = (count * 100) / filelength;
tv_info.settext("下载:" + result + "%");
} catch (exception e) {
e.printstacktrace();
}
}
}
//暂停
private boolean flag = false;//是否在下载
public void pause(view v){
flag = false;
bt_download.setenabled(true);
bt_pause.setenabled(false);
}
//下载
public void download(view v){
flag = true; //是在下载
bt_download.setenabled(false);//一点击变成不可点击
bt_pause.setenabled(true);//一点击变成可点击
new thread(){//子线程
public void run() {
try {
//获取服务器上文件的大小
httpclient client = new defaulthttpclient();
httphead request = new httphead(uri);
httpresponse response = client.execute(request);
//response 只有响应头 没有响应体
if(response.getstatusline().getstatuscode() == 200){
header[] headers = response.getheaders("content-length");
string value = headers[0].getvalue();
//文件大小
int filelength = integer.parseint(value);
log.i(tag, "filelength:"+filelength);
//设置进度条的最大值
message msg_setmax = message.obtain(mhandler, set_max, filelength, 0);
msg_setmax.sendtotarget();
//处理下载记录文件
for(int threadid=0;threadid<threadsize;threadid++){
//对应的下载记录文件
file file = new file(environment.getexternalstoragedirectory(),threadid+".txt");
//判断文件是否存在
if(!file.exists()){
//创建文件
file.createnewfile();
}
}
//在sdcard创建和服务器大小一样的文件
string name = getfilename(uri);
file file = new file(environment.getexternalstoragedirectory(),name);
//随机访问文件
randomaccessfile raf = new randomaccessfile(file, "rwd");
//设置文件的大小
raf.setlength(filelength);
//关闭
raf.close();
//计算每条线程的下载量
int block = (filelength%threadsize == 0)?(filelength/threadsize):(filelength/threadsize+1);
//开启三条线程执行下载
for(int threadid=0;threadid<threadsize;threadid++){
new downloadthread(threadid, uri, file, block).start();
}
}
} catch (exception e) {
e.printstacktrace();
}
};
}.start();
}
//线程下载类
private class downloadthread extends thread {
private int threadid;//线程的id
private string uri;//下载的地址
private file file;//下载文件
private int block;//下载的块
private int start;
private int end;
public downloadthread(int threadid, string uri, file file, int block) {
super();
this.threadid = threadid;
this.uri = uri;
this.file = file;
this.block = block;
//计算下载的开始位置和结束位置
start = threadid * block;
end = (threadid + 1) * block - 1;
try {
//读取该条线程原来的下载记录
int existdownloadlength = readdownloadinfo(threadid);
//修改下载的开始位置 从新下载
start = start + existdownloadlength;
} catch (exception e) {
e.printstacktrace();
}
}
//下载 状态码：200是普通的下载 206是分段下载 range:范围
@override
public void run() {
super.run();
try {
randomaccessfile raf = new randomaccessfile(file, "rwd");
//跳转到起始位置
raf.seek(start);
//分段下载
httpclient client = new defaulthttpclient();
httpget request = new httpget(uri);
request.addheader("range", "bytes:"+start+"-"+end);//添加请求头
httpresponse response = client.execute(request);
if(response.getstatusline().getstatuscode() == 200){
inputstream inputstream = response.getentity().getcontent();
//把流写入到文件
byte[] buffer = new byte[1024];
int len = 0;
while((len = inputstream.read(buffer)) != -1){
//如果暂停下载 点击暂停 false 就直接return 点击下载true接着下载
if(!flag){
return;//标准线程结束
}
//写数据
raf.write(buffer, 0, len);
//读取原来下载的数据量 这里读取是为了更新下载记录
int existdownloadlength = readdownloadinfo(threadid);//原来下载的数据量
//计算最新的下载
int newdownloadlength = existdownloadlength + len;
//更新下载记录 从新记录最新下载位置
updatedownloadinfo(threadid, newdownloadlength);
//更新进度条的显示 下载的百分比
message update_msg = message.obtain(mhandler, update_view, len, 0);
update_msg.sendtotarget();
//模拟 看到进度条动的效果
systemclock.sleep(50);
}
inputstream.close();
raf.close();
log.i(tag, "第"+threadid+"条线程下载完成");
}
} catch (exception e) {
e.printstacktrace();
}
}
}
/**
* 读取指定线程的下载数据量
* @param threadid 线程的id
* @return
* @throws exception
*/
public int readdownloadinfo(int threadid) throws exception{
//下载记录文件
file file = new file(environment.getexternalstoragedirectory(),threadid+".txt");
bufferedreader br = new bufferedreader(new filereader(file));
//读取一行数据
string content = br.readline();
int downlength = 0;
//如果该文件第一次创建去执行读取操作 文件里面的内容是 null
if(!textutils.isempty(content)){
downlength = integer.parseint(content);
}
//关闭流
br.close();
return downlength;
}
/**
* 更新下载记录
* @param threadid
* @param newdownloadlength
*/
public void updatedownloadinfo(int threadid,int newdownloadlength) throws exception{
//下载记录文件
file file = new file(environment.getexternalstoragedirectory(),threadid+".txt");
filewriter fw = new filewriter(file);
fw.write(newdownloadlength+"");
fw.close();
}
/**
* 获取文件的名称
* @param uri
* @return
*/
private string getfilename(string uri){
return uri.substring(uri.lastindexof("/")+1);
}
}
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