android中多线程下载实例

代码如下:

public class MainActivity extends Activity {
// 声明控件
// 路径与线程数量
private EditText et_url, et_num;
// 进度条
public static ProgressBar pb_thread;
// 显示进度的操作
private TextView tv_pb;
// 线程的数量
public static int threadNum = 3;
// 每个线程负责下载的大小
public int blockSize;
public static int threadCount;// 数量
// 访问的path
public String path;
public static boolean flag = true;
// 记录进度条的值
public static int pb_count = 0;
public static Handler handler;
public static final int TEXTVALUE = 1;
public static int pb_num = 0;
public static int size = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_url = (EditText) findViewById(R.id.et_path);
et_num = (EditText) findViewById(R.id.et_threadNum);
pb_thread = (ProgressBar) findViewById(R.id.pb_down);
tv_pb = (TextView) findViewById(R.id.tv_pb);
handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case TEXTVALUE:
System.out.println("-----------------------"
+ MainActivity.pb_count + "//////"
+ MainActivity.size);

// 改变TEXTView
pb_num = (MainActivity.pb_count * 100) / MainActivity.size;
tv_pb.setText("当前进度是+" + pb_num + "%");
break;
default:
break;
}
}
};
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
// getMenuInflater().inflate(R.menu.down, menu);
return true;
}
//下载操作
public void downLoad(View v) {
// 改变变量值：
MainActivity.flag = true;
MainActivity.pb_count = 0;
path = et_url.getText().toString();
String threadNum_et = et_num.getText().toString();
if (TextUtils.isEmpty(path) || TextUtils.isEmpty(threadNum_et)) {
Toast.makeText(this, "不能为空", Toast.LENGTH_LONG).show();
return;
}
Toast.makeText(this, "url:" + path + "--" + threadNum_et,
Toast.LENGTH_LONG).show();
// 转换成数字
threadNum = Integer.valueOf(threadNum_et);
new Thread(new Runnable() {
@Override
public void run() {
try {
// 创建出URL对象
URL url = new URL(path);
// 创建出 HttpURLConnection对象
HttpURLConnection httpURLConnection = (HttpURLConnection) url
.openConnection();
// 设置 发请求发送的方式
httpURLConnection.setRequestMethod("GET");
// 设置请求是否超时时间
httpURLConnection.setConnectTimeout(5000);
// 设置
httpURLConnection
.setRequestProperty("User-Agent",
" Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");
// 是否响应成功
if (httpURLConnection.getResponseCode() == 200) {
// 获取文件的大小
size = httpURLConnection.getContentLength();
System.out.println("文件的大小" + size);
// 设置进度条的最大值
pb_thread.setMax(size);
// 创建文件 //保存到SD卡上
// 首先判断是否拥有sdcard
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
// 获取sdCard文件目录对象
File sdFile = Environment
.getExternalStorageDirectory();
// 创建文件对象
File file = new File(sdFile, "youdao.exe");
RandomAccessFile accessFile = new RandomAccessFile(
file, "rwd");
// 设置文件的大小
accessFile.setLength(size);
// 每个线程下载的大小
blockSize = size / threadNum;
// 开三个线程 操作此文件
for (int i = 1; i <= threadNum; i++) {
// 1 2 3
// 计算出每个线程开始的位置
int startSize = (i - 1) * blockSize;
// 结束位置
int endSize = (i) * blockSize;
// 当线程是最后一个线程的时候
if (i == threadNum) {
// 判断文件的大小是否大于计算出来的结束位置
if (size > endSize) {
// 结束位置 等于 文件的大小
endSize = size;
}
}
// 为每个线程创建一个随机的读取
RandomAccessFile threadAccessFile = new RandomAccessFile(
file, "rwd");
new Thread(new DownLoadThread(i,
threadAccessFile, startSize, endSize,
path)).start();
}
}
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}).start();
}
//暂停操作
public void downPause(View v) {
Toast.makeText(this, "暂停", Toast.LENGTH_LONG).show();
this.flag = false;
}
}

代码如下:

public class DownLoadThread implements Runnable {
// 下载文件的封装
public RandomAccessFile accessFile;
// 线程下载文件的起始位置
public int startSize;
public int endSize;
// 文件下载的path路径
public String path;
public int threadId; // 线程的标识
public DownLoadThread(int threadId, RandomAccessFile accessFile,
int startSize, int endSize, String path) {
this.threadId = threadId;
this.accessFile = accessFile;
this.startSize = startSize;
this.endSize = endSize;
this.path = path;
}
@Override
public void run() {
// 执行run方法
try {
// 创建文件到SD卡上去
// 首先判断是否拥有sdcard
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
// 获取sdCard文件目录对象
File sdFile = Environment.getExternalStorageDirectory();
File threadFile = new File(sdFile, threadId + ".txt");
if (threadFile.exists()) {
// 读取该文件的内容
// 创建文件的输入流对象
FileInputStream fis = new FileInputStream(threadFile);
// 采用工具类读取
byte data[] = StreamTools.isToData(fis);
// 转化成字符串
String threadLen = new String(data);
if ((threadLen != null) && (!"".equals(threadLen))) {
startSize = Integer.valueOf(threadLen);
// 解决 416bug的错误
if (startSize > endSize) {
startSize = endSize - 1;
}
}
}
// 创建文件
// 创建URL对象
URL url = new URL(path);
// 创建HttpURLConnection对象
HttpURLConnection httpURLConnection = (HttpURLConnection) url
.openConnection();
// 设置请求的头
httpURLConnection.setRequestMethod("GET");
// 设置请求是否超时时间
httpURLConnection.setConnectTimeout(5000);
// 设置
httpURLConnection
.setRequestProperty("User-Agent",
" Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");
// 关键的设置
httpURLConnection.setRequestProperty("Range", "bytes="
+ startSize + "-" + endSize);
// 输出当前线程
System.out.println("当前线程" + threadId + " 下载开始位置:" + startSize
+ " 下载结束位置:" + endSize);
// 响应成功
// 设置随机读取文件的 开始位置
accessFile.seek(startSize);
// 获取相应流对象
InputStream is = httpURLConnection.getInputStream();
// 创建输出流对象
byte buffer[] = new byte[1024];
int len = 0;
int threadTotal = 0;// 每个线程下载后保存记录 /
while ((len = is.read(buffer)) != -1) {
accessFile.write(buffer, 0, len);
threadTotal += len;// 记录你写入的长度 //xml文件
//改变进度条：
setProgressBar(len);
// 通过文件记录文件下载的长度
FileOutputStream fos = new FileOutputStream(threadFile);
fos.write((threadTotal + "").getBytes());
fos.flush();
fos.close();
//发送handler消息
MainActivity.handler.sendEmptyMessage(MainActivity.TEXTVALUE);
if(!MainActivity.flag){
return;
}
}
accessFile.close();
is.close();
System.out.println(threadId + "线程执行完毕");
// 线程操作
synchronized (MainActivity.class) {
MainActivity.threadCount++;
if (MainActivity.threadCount >= MainActivity.threadNum) {
for (int i = 1; i <= MainActivity.threadNum; i++) {
// 获取sdCard上的文件
File deleteFile = new File(sdFile, i + ".txt");
if (deleteFile.exists()) {
// 文件删除
deleteFile.delete();
}
}
}
}
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public synchronized void setProgressBar(int len){
MainActivity.pb_count+=len;
MainActivity.pb_thread.setProgress(MainActivity.pb_count);
}

}

代码如下:

public class StreamTools {

public static byte[] isToData(InputStream is) throws IOException{
// 字节输出流
ByteArrayOutputStream bops = new ByteArrayOutputStream();
// 读取数据的缓存区
byte buffer[] = new byte[1024];
// 读取长度的记录
int len = 0;
// 循环读取
while ((len = is.read(buffer)) != -1) {
bops.write(buffer, 0, len);
}
// 把读取的内容转换成byte数组
byte data[] = bops.toByteArray();

bops.flush();
bops.close();
is.close();
return data;
}
}

完整源码