Android之多线程断点下载

缺乏、安全感 2022-07-28 04:21 153阅读 0赞

### 本文主要包含多线程下载的一些简单demo,包括三部分 ###

1.  java实现
2.  android实现
3.  XUtils开源库实现

### 注意下载添加网络权限与SD卡读写权限 ###

### java实现多线程下载 ###

public class MutileThreadDownload {
        
        /**
         * 线程的数量
         */
        private static int threadCount = 3;
    
        /**
         * 每个下载区块的大小
         */
        private static long blocksize;
    
        /**
         * 正在运行的线程的数量
         */
        private static int runningThreadCount;
    
        /**
         * @param args
         * @throws Exception
         */
        public static void main(String[] args) throws Exception {
            // 服务器文件的路径
            String path = "http://192.168.1.100:8080/ff.exe";
            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("temp.exe");
                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);
                    new DownloadThread(path, i, startIndex, endIndex).start();
                }
            }
            conn.disconnect();
        }
    
        private static 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;
                    File positionFile = new File(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();
                    }
    
                    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("temp.exe");
                    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[512];
                    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();
                    }
                    is.close();
                    raf.close();
    
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    // 只有所有的线程都下载完毕后 才可以删除记录文件。
                    synchronized (MutileThreadDownload.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(i + ".txt");
                                System.out.println(f.delete());
                            }
                        }
                    }
    
                }
            }
        }
    }

### 安卓实现 ###

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;
    
    
        @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;
            }
            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));
                            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;
                    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
        private String getFileName(String path){
            int start = path.lastIndexOf("/")+1;
            return path.substring(start);
        }
    
    }

### 利用XUtils开源框架实现，需要XUtils的jar包 ###

public class MainActivity extends Activity {
        
        private EditText et_path;
        private TextView tv_info;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            et_path = (EditText) findViewById(R.id.et_path);
            tv_info = (TextView) findViewById(R.id.tv_info);
        }
    
        public void download(View view){
            String path = et_path.getText().toString().trim();
            if(TextUtils.isEmpty(path)){
                Toast.makeText(this, "请输入下载的路径", 0).show();
                return;
            }else{
                HttpUtils http = new HttpUtils();
                HttpHandler handler = http.download(path,
                        "/sdcard/xxx.zip",
                        true, // 如果目标文件存在，接着未完成的部分继续下载。服务器不支持RANGE时将从新下载。
                        true, // 如果从请求返回信息中获取到文件名，下载完成后自动重命名。
                        new RequestCallBack<File>() {
    
                            @Override
                            public void onStart() {
                                tv_info.setText("conn...");
                            }
    
                            @Override
                            public void onLoading(long total, long current, boolean isUploading) {
                                tv_info.setText(current + "/" + total);
                            }
    
                            @Override
                            public void onSuccess(ResponseInfo<File> responseInfo) {
                                tv_info.setText("downloaded:" + responseInfo.result.getPath());
                            }
                            @Override
                            public void onFailure(HttpException error, String msg) {
                                tv_info.setText(msg);
                            }
                    });
            }
        }
    }

### 完成 ###