Fast Implementation of Breakpoint Continued Transmission in Android
- 2021-09-20 21:33:54
- OfStack
In this paper, we share the specific code of Android to quickly realize breakpoint continuous transmission for your reference. The specific contents are as follows
1. Import dependencies
compile 'com.loopj.android:android-async-http:1.4.9'2. Import permissions
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
3. Layout files
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.five.fashion.duandianxuchuan.MainActivity">
<ProgressBar
style="@style/Widget.AppCompat.ProgressBar.Horizontal"
android:layout_width="match_parent"
android:layout_height="100dp"
android:id="@+id/pb"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tv_info"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=" Download "
android:id="@+id/bt_download"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=" Suspend "
android:id="@+id/bt_pause"
/>
</LinearLayout>
4. Main code
package com.five.fashion.duandianxuchuan;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.loopj.android.http.HttpGet;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.RandomAccessFile;
import cz.msebera.android.httpclient.Header;
import cz.msebera.android.httpclient.HttpResponse;
import cz.msebera.android.httpclient.client.HttpClient;
import cz.msebera.android.httpclient.client.methods.HttpHead;
import cz.msebera.android.httpclient.impl.client.DefaultHttpClient;
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(@Nullable 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();
}
}
bt_download.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
download(v);
}
});
bt_pause.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
pause(v);
}
});
}
//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);//1点击变成不可点击
bt_pause.setEnabled(true);//1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1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3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1行数据
String content = br.readLine();
int downlength = 0;
//如果该文件第1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);
}
}