多线程下载的实现
原理见: 开源代码XUtils2的使用,多线程断点下载,get,post,数据库
MainActivity
import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.os.Handler; import android.os.Message; import android.text.TextUtils; import android.view.View; import android.widget.EditText; import android.widget.LinearLayout; import android.widget.ProgressBar; import android.widget.Toast; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.List; 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", Toast.LENGTH_SHORT).show(); break; case THREAD_ERROR: Toast.makeText(getApplicationContext(), "下载失败,请重试",Toast.LENGTH_SHORT).show(); break; case DWONLOAD_FINISH: Toast.makeText(getApplicationContext(), "下载完成",Toast.LENGTH_SHORT).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", Toast.LENGTH_SHORT).show(); return; } String count = et_count.getText().toString().trim(); if(TextUtils.isEmpty(count)){ Toast.makeText(this, "对不起,线程数量不能为空", Toast.LENGTH_SHORT).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);//按照线程数添加进度条 } Toast.makeText(this, "开始下载", Toast.LENGTH_SHORT).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,为文件总大小减1 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);//为对应的精度条设置最大的进度值 new DownloadThread(path, i, startIndex, endIndex).start();//开启线程下载 } } conn.disconnect();//断开连接,这个线程只是用来分配下载任务的,具体下载为上面的线程 } catch (Exception e) { e.printStackTrace(); Message msg = Message.obtain(); msg.what = DOWNLOAD_ERROR; handler.sendMessage(msg); } }; }.start(); } /** * 根据开始位置,结束位置,线程名,路径开始下载 */ private class DownloadThread extends Thread { private int threadId; private long startIndex; private long endIndex; private String path;//文件的下载地址 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; //创建一个文件来记录这个线程已经下载的字节(文件名与线程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。从这个位置开始下载 fis.close(); //也可以将数据存数据库。 //_id path threadid total } //指定这个线程只请求指定的字节数 conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex); conn.setConnectTimeout(5000); int code = conn.getResponseCode(); System.out.println("code=" + code);//多个线程连接成功的状态码为206 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) { raf.write(buffer, 0, len);//下载的数据 total += len;//记录总长度 RandomAccessFile rf = new RandomAccessFile(positionFile, "rwd"); rf.write(String.valueOf(total).getBytes());//将下载的位置记录下来,写进文件 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); } } } } } /** * 根据文件的下载地址,获取文件名,做为下载的命名 */ private String getFileName(String path){ int start = path.lastIndexOf("/")+1; return path.substring(start); } }
布局文件:activity_main.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" 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 存放进度条 android:id="@+id/ll_container" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > </LinearLayout> </LinearLayout>
进度条布局:pb.xml
<?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" />
