android中多线程下载实例

2020-04-11 12:06:41

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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; 
} 
} 

复制代码代码如下:

 
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); 
} 



} 

复制代码代码如下:

 
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; 
} 
} 