多线程下载的移植

1.界面

1.      判断SD卡的内存是否够用

2.      动态添加进度条：

 建一个空白的Linearlayout，动态添加；也可以添加一个xml布局；

动态清空Linearlayout中的布局，removeAllViews()

3.       进度条可以在子线程中修改，因为进度条已经封装了handler方法

4.      企业一般不用文件存进度，会用数据库存

代码：

public class MainActivity extends Activity {protected static final int DOWNLOAD_ERROR = 1;private static final int THREAD_ERROR = 2;public static final int DWONLOAD_FINISH = 3;private EditText et_path;private EditText et_count;/** * 存放进度条的布局 */private LinearLayout ll_container;/** * 进度条的集合 */private List<ProgressBar> pbs;/** * android下的消息处理器，在主线程创建，才可以更新ui */private Handler handler = new Handler(){public void handleMessage(Message msg) {switch (msg.what) {case DOWNLOAD_ERROR:Toast.makeText(getApplicationContext(), "下载失败", 0).show();break;case THREAD_ERROR:Toast.makeText(getApplicationContext(), "下载失败,请重试", 0).show();break;case DWONLOAD_FINISH:Toast.makeText(getApplicationContext(), "下载完成", 0).show();break;}};};/** * 线程的数量 */private int threadCount = 3;/** * 每个下载区块的大小 */private long blocksize;/** * 正在运行的线程的数量 */private  int runningThreadCount;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);et_path = (EditText) findViewById(R.id.et_path);et_count = (EditText) findViewById(R.id.et_count);ll_container = (LinearLayout) findViewById(R.id.ll_container);}/** * 下载按钮的点击事件 * @param view */public void downLoad(View view){//下载文件的路径final String path = et_path.getText().toString().trim();if(TextUtils.isEmpty(path)){Toast.makeText(this, "对不起下载路径不能为空", 0).show();return;}String count = et_count.getText().toString().trim();if(TextUtils.isEmpty(path)){Toast.makeText(this, "对不起,线程数量不能为空", 0).show();return;}threadCount = Integer.parseInt(count);//清空掉旧的进度条ll_container.removeAllViews();//在界面里面添加count个进度条pbs = new ArrayList<ProgressBar>();for(int j=0;j<threadCount;j++){ProgressBar pb = (ProgressBar) View.inflate(this, R.layout.pb, null);ll_container.addView(pb);pbs.add(pb);}Toast.makeText(this, "开始下载", 0).show();new Thread(){public void run() {try {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);int code = conn.getResponseCode();if (code == 200) {long size = conn.getContentLength();// 得到服务端返回的文件的大小System.out.println("服务器文件的大小：" + size);blocksize = size / threadCount;// 1.首先在本地创建一个大小跟服务器一模一样的空白文件。File file = new File(Environment.getExternalStorageDirectory(),getFileName(path));//不写死文件名RandomAccessFile raf = new RandomAccessFile(file, "rw");raf.setLength(size);// 2.开启若干个子线程分别去下载对应的资源。runningThreadCount = threadCount;for (int i = 1; i <= threadCount; i++) {long startIndex = (i - 1) * blocksize;long endIndex = i * blocksize - 1;if (i == threadCount) {// 最后一个线程endIndex = size - 1;}System.out.println("开启线程：" + i + "下载的位置：" + startIndex + "~"+ endIndex);int threadSize = (int) (endIndex - startIndex);pbs.get(i-1).setMax(threadSize);new DownloadThread(path, i, startIndex, endIndex).start();}}conn.disconnect();} catch (Exception e) {e.printStackTrace();Message msg = Message.obtain();msg.what = DOWNLOAD_ERROR;handler.sendMessage(msg);}};}.start();}private class DownloadThread extends Thread {private int threadId;private long startIndex;private long endIndex;private String path;public DownloadThread(String path, int threadId, long startIndex,long endIndex) {this.path = path;this.threadId = threadId;this.startIndex = startIndex;this.endIndex = endIndex;}@Overridepublic void run() {try {// 当前线程下载的总大小int total = 0;File positionFile = new File(Environment.getExternalStorageDirectory(),getFileName(path)+threadId + ".txt");URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");// 接着从上一次的位置继续下载数据if (positionFile.exists() && positionFile.length() > 0) {// 判断是否有记录FileInputStream fis = new FileInputStream(positionFile);BufferedReader br = new BufferedReader(new InputStreamReader(fis));// 获取当前线程上次下载的总大小是多少String lasttotalstr = br.readLine();int lastTotal = Integer.valueOf(lasttotalstr);System.out.println("上次线程" + threadId + "下载的总大小："+ lastTotal);startIndex += lastTotal;total += lastTotal;// 加上上次下载的总大小。fis.close();//存数据库。//_id path threadid total}conn.setRequestProperty("Range", "bytes=" + startIndex + "-"+ endIndex);conn.setConnectTimeout(5000);int code = conn.getResponseCode();System.out.println("code=" + code);InputStream is = conn.getInputStream();File file = new File(Environment.getExternalStorageDirectory(),getFileName(path));RandomAccessFile raf = new RandomAccessFile(file, "rw");// 指定文件开始写的位置。raf.seek(startIndex);System.out.println("第" + threadId + "个线程：写文件的开始位置："+ String.valueOf(startIndex));int len = 0;byte[] buffer = new byte[1024];while ((len = is.read(buffer)) != -1) {RandomAccessFile rf = new RandomAccessFile(positionFile,"rwd");raf.write(buffer, 0, len);total += len;rf.write(String.valueOf(total).getBytes());rf.close();pbs.get(threadId-1).setProgress(total);}is.close();raf.close();} catch (Exception e) {e.printStackTrace();Message msg = Message.obtain();msg.what = THREAD_ERROR;handler.sendMessage(msg);} finally {// 只有所有的线程都下载完毕后 才可以删除记录文件。synchronized (MainActivity.class) {System.out.println("线程" + threadId + "下载完毕了");runningThreadCount--;if (runningThreadCount < 1) {System.out.println("所有的线程都工作完毕了。删除临时记录的文件");for (int i = 1; i <= threadCount; i++) {File f = new File(Environment.getExternalStorageDirectory(),getFileName(path)+ i + ".txt");System.out.println(f.delete());}Message msg = Message.obtain();msg.what = DWONLOAD_FINISH;handler.sendMessage(msg);}}}}}//http://192.168.1.100:8080/aa.exeprivate String getFileName(String path){int start = path.lastIndexOf("/")+1;return path.substring(start);}}