初学者--Andorid 断点续传

港控/mmm° 2022-06-06 13:52 242阅读 0赞

1.在module的build.gradle文件的

dependencies {

导入依赖:

compile 'com.loopj.android:android-async-http:1.4.9'

2.权限:

<uses-permission android:name="android.permission.INTERNET"/>
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

3.activity\_main.xml布局文件

4.MainActivity文件代码:

import android.os.Environment;
    import android.os.Handler;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.widget.Button;
    import android.widget.ImageView;
    import android.widget.ProgressBar;
    import android.widget.TextView;
    import android.os.Environment;
    import android.os.Message;
    import android.os.SystemClock;
    import android.support.annotation.Nullable;
    import android.text.TextUtils;
    import android.util.Log;
    import android.view.View;
    import android.widget.Button;
    import android.widget.ProgressBar;
    import android.widget.TextView;
    import android.widget.Toast;
    
    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileReader;
    import java.io.FileWriter;
    import java.io.InputStream;
    import java.io.RandomAccessFile;
    
    import cz.msebera.android.httpclient.Header;
    import cz.msebera.android.httpclient.HttpResponse;
    import cz.msebera.android.httpclient.client.HttpClient;
    import cz.msebera.android.httpclient.client.methods.HttpGet;
    import cz.msebera.android.httpclient.client.methods.HttpHead;
    import cz.msebera.android.httpclient.impl.client.DefaultHttpClient;
    
    public class MainActivity extends AppCompatActivity {
    
        protected static final String TAG = "MainActivity";
    
        //下载线程的数量
        private final static int threadsize = 3;
    
        protected static final int SET_MAX = 0;
        public static final int UPDATE_VIEW = 1;
    
        private ProgressBar pb;
        private Button bt_download;
    
        private Button bt_pause;
        private TextView tv_info;
    
        
        //显示进度和更新进度
        private Handler mHandler = new Handler(){
            public void handleMessage(android.os.Message msg) {
                switch (msg.what) {
                    case SET_MAX://设置进度条的最大值
                        int filelength = msg.arg1;
                        pb.setMax(filelength);
                        break;
                    case UPDATE_VIEW://更新进度条  和 下载的比率
                        int len = msg.arg1;//新下载的长度
                        pb.setProgress(pb.getProgress()+len);//设置进度条的刻度
    
                        int max = pb.getMax();//获取进度的最大值
                        int progress = pb.getProgress();//获取已经下载的数据量
                        //  下载：30    总：100
                        int result = (progress*100)/max;
    
                        tv_info.setText("下载:"+result+"%");
                        break;
    
                    default:
                        break;
                }
            }
    
        };
    
    //    String uri = "http://c.hiphotos.baidu.com/image/pic/item/b90e7bec54e736d1e51217c292504fc2d46269f3.jpg";
    //    String uri = "https://codeload.github.com/open-android/Zxing/zip/master";
        String uri = "https://raw.githubusercontent.com/open-android/Zxing/master/screenshot1.gif";
    
    
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            initView();
    
            //数据的回显
            //确定下载的文件
            String name = getFileName(uri);
            File file = new File(Environment.getExternalStorageDirectory(), name);
            if (file.exists()){//文件存在回显
                //获取文件的大小
                int filelength = (int) file.length();
                pb.setMax(filelength);
                try {
                    //统计原来所有的下载量
                    int count = 0;
                    //读取下载记录文件
                    for (int threadid = 0; threadid < threadsize; threadid++) {
                        //获取原来指定线程的下载记录
                        int existDownloadLength = readDownloadInfo(threadid);
                        count = count + existDownloadLength;
                    }
                    //设置进度条的刻度
                    pb.setProgress(count);
    
                    //计算比率
                    int result = (count * 100) / filelength;
                    tv_info.setText("下载:" + result + "%");
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    
        }
        private void initView() {
            pb = (ProgressBar) findViewById(R.id.progressBar);
            bt_download = (Button) findViewById(R.id.download);
            bt_pause = (Button) findViewById(R.id.stop);
            tv_info = (TextView) findViewById(R.id.text);
        }
    
    
        //暂停
        private boolean flag = false;//是否在下载
    
        public void pause(View v){
            Toast.makeText(MainActivity.this,"暂停",Toast.LENGTH_SHORT).show();
            flag = false;
            bt_download.setEnabled(true);
            bt_pause.setEnabled(false);
        }
    
        //下载
        public void download(View v){
            Toast.makeText(MainActivity.this,"开始下载",Toast.LENGTH_SHORT).show();
            flag = true; //是在下载
            bt_download.setEnabled(false);//一点击变成不可点击
            bt_pause.setEnabled(true);//一点击变成可点击
            new Thread(){//子线程
                public void run() {
                    try {
                        //获取服务器上文件的大小
                        HttpClient client = new DefaultHttpClient();
                        HttpHead request = new HttpHead(uri);
                        HttpResponse response = client.execute(request);
                        //response  只有响应头  没有响应体
                        if(response.getStatusLine().getStatusCode() == 200){
                            Header[] headers = response.getHeaders("Content-Length");
                            String value = headers[0].getValue();
                            //文件大小
                            int filelength = Integer.parseInt(value);
                            Log.i(TAG, "filelength:"+filelength);
    
                            //设置进度条的最大值
                            Message msg_setmax = Message.obtain(mHandler, SET_MAX, filelength, 0);
                            msg_setmax.sendToTarget();
    
    
                            //处理下载记录文件
                            for(int threadid=0;threadid<threadsize;threadid++){
                                //对应的下载记录文件
                                File file = new File(Environment.getExternalStorageDirectory(),threadid+"断点续传下载记录log.txt");
                                //判断文件是否存在
                                if(!file.exists()){
                                    //创建文件
                                    file.createNewFile();
                                }
                            }
    
                            //在sdcard创建和服务器大小一样的文件
                            String name = getFileName(uri);
                            File file = new File(Environment.getExternalStorageDirectory(),name);
                            //随机访问文件
                            RandomAccessFile raf = new RandomAccessFile(file, "rwd");
                            //设置文件的大小
                            raf.setLength(filelength);
                            //关闭
                            raf.close();
    
                            //计算每条线程的下载量
                            int block = (filelength%threadsize == 0)?(filelength/threadsize):(filelength/threadsize+1);
    
                            //开启三条线程执行下载
                            for(int threadid=0;threadid<threadsize;threadid++){
                                new DownloadThread(threadid, uri, file, block).start();
                            }
    
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }.start();
        }
    
    
        //线程下载类
        private class DownloadThread extends Thread{
            private int threadid;//线程的id
            private String uri;//下载的地址
            private File file;//下载文件
            private int block;//下载的块
            private int start;
            private int end;
    
            public DownloadThread(int threadid, String uri, File file, int block) {
                super();
                this.threadid = threadid;
                this.uri = uri;
                this.file = file;
                this.block = block;
                //计算下载的开始位置和结束位置
                start = threadid * block;
                end = (threadid + 1)*block -1;
    
                try {
                    //读取该条线程原来的下载记录
                    int existDownloadLength = readDownloadInfo(threadid);
    
                    //修改下载的开始位置   从新下载
                    start = start + existDownloadLength;
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    
    
            //下载   状态码：200是普通的下载      206是分段下载        Range:范围
            @Override
            public void run() {
                super.run();
                try {
                    RandomAccessFile raf = new RandomAccessFile(file, "rwd");
                    //跳转到起始位置
                    raf.seek(start);
    
                    //分段下载
                    HttpClient client = new DefaultHttpClient();
                    HttpGet request = new HttpGet(uri);
                    request.addHeader("Range", "bytes:"+start+"-"+end);//添加请求头
                    HttpResponse response = client.execute(request);
                    if(response.getStatusLine().getStatusCode() == 200){
                        InputStream inputStream = response.getEntity().getContent();
                        //把流写入到文件
                        byte[] buffer = new byte[1024];
                        int len = 0;
                        while((len = inputStream.read(buffer)) != -1){
                            //如果暂停下载  点击暂停 false 就直接return 点击下载true接着下载
                            if(!flag){
                                return;//标准线程结束
                            }
                            //写数据
                            raf.write(buffer, 0, len);
    
                            //读取原来下载的数据量 这里读取是为了更新下载记录
                            int existDownloadLength = readDownloadInfo(threadid);//原来下载的数据量
    
                            //计算最新的下载
                            int newDownloadLength = existDownloadLength + len;
    
                            //更新下载记录 从新记录最新下载位置
                            updateDownloadInfo(threadid, newDownloadLength);
    
                            //更新进度条的显示   下载的百分比
                            Message update_msg = Message.obtain(mHandler, UPDATE_VIEW, len, 0);
                            update_msg.sendToTarget();
                            //模拟  看到进度条动的效果
                            SystemClock.sleep(50);
                        }
                        inputStream.close();
                        raf.close();
                        Log.i(TAG, "第"+threadid+"条线程下载完成");
                    }
    
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    
    
        /**
         * 读取指定线程的下载数据量
         * @param threadid  线程的id
         * @return
         * @throws Exception
         */
        public int readDownloadInfo(int threadid) throws Exception{
            //下载记录文件
            File file = new File(Environment.getExternalStorageDirectory(),threadid+"断点续传下载记录log.txt");
            BufferedReader br = new BufferedReader(new FileReader(file));
            //读取一行数据
            String content = br.readLine();
    
            int downlength = 0;
            //如果该文件第一次创建去执行读取操作  文件里面的内容是 null
            if(!TextUtils.isEmpty(content)){
                downlength = Integer.parseInt(content);
            }
            //关闭流
            br.close();
            return downlength;
        }
    
    
        /**
         * 更新下载记录
         * @param threadid
         * @param newDownloadLength
         */
        public void updateDownloadInfo(int threadid,int newDownloadLength) throws Exception{
            //下载记录文件
            File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt");
            FileWriter fw = new FileWriter(file);
            fw.write(newDownloadLength+"");
            fw.close();
        }
    
        /**
         * 获取文件的名称
         * @param uri
         * @return
         */
        private String getFileName(String uri){
            return uri.substring(uri.lastIndexOf("/")+1);
        }
    
    }

效果:

![20171110142618009][]

![20171110142632452][]

[20171110142618009]: /images/20220606/6b5604abe18d4e57a94174a69630e038.png
[20171110142632452]: /images/20220606/5f98b06d6dc547ee8cbb0e493625e129.png