Android多線程實現文件斷點下載
download_main_layout.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:id="@+id/down_load_edt"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:hint="請輸入下載文件的網址!" />
<Button
android:layout_marginTop="20dp"
android:id="@+id/down_load_btn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="點擊下載" />
<ProgressBar
android:id="@+id/down_load_pbar"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
下載入口Activity:
public class MainActivity extends Activity implements OnClickListener {
/**下載文件按鈕 */
private Button downLoadBtn;
/**下載文件地址 */
private EditText downLoadEdt;
/**下載進度 */
private ProgressBar downLoadPbar;
/**定義發送消息的字段*/
private static final int MESSAGE_NUMBER = 1;
/**所要下載文件總大小 */
private int fileSize;
/**已下載大小 */
private int downLoadSize;
/**所下載文件的保存路徑 */
private String path;
/**更新進度條的值 */
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg.what == MESSAGE_NUMBER) {
/**設置進度*/
downLoadPbar.setProgress(Double.valueOf(downLoadSize * 1.0 / fileSize * 100).intValue());
}
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.download_activity_main);
findViews();
setListeners();
initdata();
}
private void findViews() {
downLoadEdt=(EditText) findViewById(R.id.down_load_edt);
downLoadBtn = (Button) findViewById(R.id.down_load_btn);
downLoadPbar = (ProgressBar) findViewById(R.id.down_load_pbar);
}
private void setListeners() {
downLoadBtn.setOnClickListener(this);
}
private void initdata() {
downLoadPbar.setVisibility(View.GONE);
downLoadPbar.setMax(100);
downLoadPbar.setProgress(0);
}
@Override
public void onClick(View v) {
/**獲取SDcard */
path = Environment.getExternalStorageDirectory() + "/downloads/";
File file = new File(path);
if (!file.exists()) {
file.mkdir();
}
/**下載操作 */
new Thread(new DownLoadTask()).start();
/**顯示進度條 */
downLoadPbar.setVisibility(View.VISIBLE);
}
/**子線程,計算下載量,更新UI */
class DownLoadTask implements Runnable {
/**線程塊大小,每個線程的下載量 */
private int blockSize;
/** 默認為5個線程 */
private int threadNum = 5;
/** 下載后的文件名 */
private String fileName = "myDownLoad.zip";
@Override
public void run() {
/**數組保存線程對象，便于后面的每個線程下載量計算總和 */
DownLoadThread[] fileDownLoads = new DownLoadThread[threadNum];
/** 計算總大小 */
URL url;
try {
url = new URL(downLoadEdt.getText().toString().trim());
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
/**計算下載量 */
fileSize = conn.getContentLength();
/** 計算每個線程的下載量 */
blockSize = fileSize / threadNum;
/** 執行下載操作 */
for (int i = 0; i < threadNum; i++) {
/** 每個線程的開始位置 */
int begin = i * blockSize;
/** 每個線程的結束位置 */
int end = (i + 1) * blockSize - 1;
DownLoadThread thread = new DownLoadThread(url, begin, end, path + fileName);
thread.start();
fileDownLoads[i] = thread;
}
/** 更新UI */
boolean flag = false;
while (!flag) {
flag = true;
for (int i = 0; i < threadNum; i++) {
downLoadSize += fileDownLoads[i].getDownloadsize();
if (!fileDownLoads[i].isFinish()) {
flag = false;
}
}
MainActivity.this.handler.sendEmptyMessage(MESSAGE_NUMBER);
Thread.sleep(1000);
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
下載線程工具類：
public class DownLoadThread extends Thread {
/**文件年在Url*/
private URL url;
/**文件下載開始位置*/
private int startPostion;
/**文件下載結束位置*/
private int endPostion;
/**文件下載當前位置*/
private int currentPostion;
/**文件名*/
private String filename;
/**緩沖輸入流*/
private BufferedInputStream buffin;
/**寫入流，支持斷點*/
private RandomAccessFile raf;
/**緩沖大小*/
byte[] buffsize = new byte[1024];
/**已經下載大小*/
private int downloadsize;
/**下載是否完成*/
private boolean isFinish;
public int getDownloadsize() {
return downloadsize;
}
public boolean isFinish() {
return isFinish;
}
public DownLoadThread(URL url, int begin, int end, String filename) {
super();
this.url = url;
this.startPostion = begin;
this.endPostion = end;
this.filename = filename;
}
@Override
public void run() {
try {
/**
* 抽象類 URLConnection 是所有類的超類，它代表應用程序和 URL 之間的通信鏈接。此類的實例可用于讀取和寫入此 URL 引用的資源。通常，創建一個到 URL 的連接需要幾個步驟：
* openConnection() connect()對影響到遠程資源連接的參數進行操作。 與資源交互；查詢頭字段和內容。
* 通過在 URL 上調用 openConnection 方法創建連接對象。 處理設置參數和一般請求屬性。 使用 connect 方法建立到遠程對象的實際連接。 遠程對象變為可用。遠程對象的頭字段和內容變為可訪問。
*/
URLConnection conn = url.openConnection();
/**指定下載的范圍*/
conn.setRequestProperty("Range", "bytes="+startPostion+"-"+endPostion);
/**此URL將在一定的上下文環境中被檢驗，是否允許用戶交互，比如彈出一個認證對話框。如果為 false，那么不允許用戶交互。*/
conn.setAllowUserInteraction(true);
/**做緩沖優化處理*/
buffin = new BufferedInputStream(conn.getInputStream());
/**寫入本地文件*/
raf = new RandomAccessFile(new File(filename), "rw");
/**移動到新的位置*/
raf.seek(startPostion);
while(currentPostion<endPostion){//如果當前下載沒有結束
int size = buffin.read(buffsize, 0, 1024);
/**已經讀完*/
if(size==-1){
break;
}
raf.write(buffsize, 0, size);
currentPostion+=size;
/**下載量*/
downloadsize+=size;
}
isFinish = true;
/**下載完成就要關閉輸入流與寫入流*/
buffin.close();
raf.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
super.run();
}
}
不要忘記在清單文件AndroidManifest.xml中設置相應權限：
<!-- 網絡訪問權限 --><uses-permission android:name="android.permission.INTERNET" />
<!-- sdcard權限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />