android中多線程下載實例

復制代碼 代碼如下:
public class MainActivity extends Activity {
// 聲明控件
// 路徑與線程數量
private EditText et_url, et_num;
// 進度條
public static ProgressBar pb_thread;
// 顯示進度的操作
private TextView tv_pb;
// 線程的數量
public static int threadNum = 3;
// 每個線程負責下載的大小
public int blockSize;
public static int threadCount;// 數量
// 訪問的path
public String path;
public static boolean flag = true;
// 記錄進度條的值
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);

// 改變TEXTView
pb_num = (MainActivity.pb_count * 100) / MainActivity.size;
tv_pb.setText("當前進度是+" + 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;
}
//下載操作
public void downLoad(View v) {
// 改變變量值：
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, "不能為空", Toast.LENGTH_LONG).show();
return;
}
Toast.makeText(this, "url:" + path + "--" + threadNum_et,
Toast.LENGTH_LONG).show();
// 轉換成數字
threadNum = Integer.valueOf(threadNum_et);
new Thread(new Runnable() {
@Override
public void run() {
try {
// 創建出URL對象
URL url = new URL(path);
// 創建出 HttpURLConnection對象
HttpURLConnection httpURLConnection = (HttpURLConnection) url
.openConnection();
// 設置 發請求發送的方式
httpURLConnection.setRequestMethod("GET");
// 設置請求是否超時時間
httpURLConnection.setConnectTimeout(5000);
// 設置
httpURLConnection
.setRequestProperty("User-Agent",
" Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");
// 是否響應成功
if (httpURLConnection.getResponseCode() == 200) {
// 獲取文件的大小
size = httpURLConnection.getContentLength();
System.out.println("文件的大小" + size);
// 設置進度條的最大值
pb_thread.setMax(size);
// 創建文件 //保存到SD卡上
// 首先判斷是否擁有sdcard
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
// 獲取sdCard文件目錄對象
File sdFile = Environment
.getExternalStorageDirectory();
// 創建文件對象
File file = new File(sdFile, "youdao.exe");
RandomAccessFile accessFile = new RandomAccessFile(
file, "rwd");
// 設置文件的大小
accessFile.setLength(size);
// 每個線程下載的大小
blockSize = size / threadNum;
// 開三個線程 操作此文件
for (int i = 1; i <= threadNum; i++) {
// 1 2 3
// 計算出每個線程開始的位置
int startSize = (i - 1) * blockSize;
// 結束位置
int endSize = (i) * blockSize;
// 當線程是最後一個線程的時候
if (i == threadNum) {
// 判斷文件的大小是否大於計算出來的結束位置
if (size > endSize) {
// 結束位置 等於 文件的大小
endSize = size;
}
}
// 為每個線程創建一個隨機的讀取
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();
}
//暫停操作
public void downPause(View v) {
Toast.makeText(this, "暫停", Toast.LENGTH_LONG).show();
this.flag = false;
}
}

復制代碼 代碼如下:
public class DownLoadThread implements Runnable {
// 下載文件的封裝
public RandomAccessFile accessFile;
// 線程下載文件的起始位置
public int startSize;
public int endSize;
// 文件下載的path路徑
public String path;
public int threadId; // 線程的標識
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() {
// 執行run方法
try {
// 創建文件到SD卡上去
// 首先判斷是否擁有sdcard
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
// 獲取sdCard文件目錄對象
File sdFile = Environment.getExternalStorageDirectory();
File threadFile = new File(sdFile, threadId + ".txt");
if (threadFile.exists()) {
// 讀取該文件的內容
// 創建文件的輸入流對象
FileInputStream fis = new FileInputStream(threadFile);
// 采用工具類讀取
byte data[] = StreamTools.isToData(fis);
// 轉化成字符串
String threadLen = new String(data);
if ((threadLen != null) && (!"".equals(threadLen))) {
startSize = Integer.valueOf(threadLen);
// 解決 416bug的錯誤
if (startSize > endSize) {
startSize = endSize - 1;
}
}
}
// 創建文件
// 創建URL對象
URL url = new URL(path);
// 創建HttpURLConnection對象
HttpURLConnection httpURLConnection = (HttpURLConnection) url
.openConnection();
// 設置請求的頭
httpURLConnection.setRequestMethod("GET");
// 設置請求是否超時時間
httpURLConnection.setConnectTimeout(5000);
// 設置
httpURLConnection
.setRequestProperty("User-Agent",
" Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");
// 關鍵的設置
httpURLConnection.setRequestProperty("Range", "bytes="
+ startSize + "-" + endSize);
// 輸出當前線程
System.out.println("當前線程" + threadId + " 下載開始位置:" + startSize
+ " 下載結束位置:" + endSize);
// 響應成功
// 設置隨機讀取文件的 開始位置
accessFile.seek(startSize);
// 獲取相應流對象
InputStream is = httpURLConnection.getInputStream();
// 創建輸出流對象
byte buffer[] = new byte[1024];
int len = 0;
int threadTotal = 0;// 每個線程下載後保存記錄 /
while ((len = is.read(buffer)) != -1) {
accessFile.write(buffer, 0, len);
threadTotal += len;// 記錄你寫入的長度 //xml文件
//改變進度條：
setProgressBar(len);
// 通過文件記錄文件下載的長度
FileOutputStream fos = new FileOutputStream(threadFile);
fos.write((threadTotal + "").getBytes());
fos.flush();
fos.close();
//發送handler消息
MainActivity.handler.sendEmptyMessage(MainActivity.TEXTVALUE);
if(!MainActivity.flag){
return;
}
}
accessFile.close();
is.close();
System.out.println(threadId + "線程執行完畢");
// 線程操作
synchronized (MainActivity.class) {
MainActivity.threadCount++;
if (MainActivity.threadCount >= MainActivity.threadNum) {
for (int i = 1; i <= MainActivity.threadNum; i++) {
// 獲取sdCard上的文件
File deleteFile = new File(sdFile, i + ".txt");
if (deleteFile.exists()) {
// 文件刪除
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);
}



}

復制代碼 代碼如下:
public class StreamTools {

public static byte[] isToData(InputStream is) throws IOException{
// 字節輸出流
ByteArrayOutputStream bops = new ByteArrayOutputStream();
// 讀取數據的緩存區
byte buffer[] = new byte[1024];
// 讀取長度的記錄
int len = 0;
// 循環讀取
while ((len = is.read(buffer)) != -1) {
bops.write(buffer, 0, len);
}
// 把讀取的內容轉換成byte數組
byte data[] = bops.toByteArray();

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

完整源碼