android（25）（android下实现多线程断点下载）

1.布局文件：<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"    tools:context=".MainActivity" >    <TextView        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="请输入下载文件的路径" />    <EditText        android:id="@+id/et_path"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="http://192.168.1.100:8080/" />    <TextView        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="请输入线程的数量" />    <EditText        android:id="@+id/et_count"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:inputType="number"        android:text="3" />    <Button        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:onClick="downLoad"        android:text="下载" />    <LinearLayout        android:id="@+id/ll_container"        android:orientation="vertical"        android:layout_width="fill_parent"        android:layout_height="fill_parent" >    </LinearLayout></LinearLayout>进度条的布局：<?xml version="1.0" encoding="utf-8"?><ProgressBar xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/progressBar1"    style="?android:attr/progressBarStyleHorizontal"    android:layout_width="fill_parent"    android:layout_height="wrap_content" />业务逻辑代码的实现：public class MainActivity extends Activity {    protected static final int DOWNLOAD_ERROR = 1;//下载错误    private static final int THREAD_ERROR = 2;//线程数量错误    public static final int DWONLOAD_FINISH = 3;//下载完毕    private EditText et_path;//url路径    private EditText et_count;//线程数量    /** * 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;    @Override    protected 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;        }        //开启线程的数量        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（线性布局清理掉所有的视图）        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);//把进度条添加到现行布局的容器中            pbs.add(pb);//把进度条添加到进度条集合中。        }        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));                        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;        }        @Override        public void run() {            try {                // 当前线程下载的总大小                int total = 0;                //下载的进度信息存储到一个文本文件中。以线程id命名。                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.exe    //根据路径名称得到文件名称    private String getFileName(String path){        int start = path.lastIndexOf("/")+1;        return path.substring(start);    }
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