Android开发之多线程下载、断点续传、进度条和文本显示
2015-12-20 22:49
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代码实现了在Android环境下的多线程下载、断点续传、进度条显示和文本显示百分数:
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 android.os.Bundle; import android.os.Environment; import android.os.Handler; import android.app.Activity; import android.view.Menu; import android.view.View; import android.widget.ProgressBar; import android.widget.TextView; public class MainActivity extends Activity { static int ThreadCount = 3; static int finishedThread = 0; int currentProgress; String fileName = "QQPlayer.exe"; //确定下载地址 String path = "http://192.168.13.13:8080/" + fileName; private ProgressBar pb; TextView tv; Handler handler = new Handler(){ public void handleMessage(android.os.Message msg) { //把变量改成long,在long下运算 tv.setText((long)pb.getProgress() * 100 / pb.getMax() + "%"); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); pb = (ProgressBar) findViewById(R.id.pb); tv = (TextView) findViewById(R.id.tv); } public void click(View v){ Thread t = new Thread(){ @Override public void run() { //发送get请求,请求这个地址的资源 try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); conn.setReadTimeout(5000); if(conn.getResponseCode() == 200){ //拿到所请求资源文件的长度 int length = conn.getContentLength(); //设置进度条的最大值就是原文件的总长度 pb.setMax(length); File file = new File(Environment.getExternalStorageDirectory(), fileName); //生成临时文件 RandomAccessFile raf = new RandomAccessFile(file, "rwd"); //设置临时文件的大小 raf.setLength(length); raf.close(); //计算出每个线程应该下载多少字节 int size = length / ThreadCount; for (int i = 0; i < ThreadCount; i++) { //计算线程下载的开始位置和结束位置 int startIndex = i * size; int endIndex = (i + 1) * size - 1; //如果是最后一个线程,那么结束位置写死 if(i == ThreadCount - 1){ endIndex = length - 1; } // System.out.println("线程" + i + "的下载区间是:" + startIndex + "---" + endIndex); new DownLoadThread(startIndex, endIndex, i).start(); } } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }; t.start(); } class DownLoadThread extends Thread{ int startIndex; int endIndex; int threadId; public DownLoadThread(int startIndex, int endIndex, int threadId) { super(); this.startIndex = startIndex; this.endIndex = endIndex; this.threadId = threadId; } @Override public void run() { //再次发送http请求,下载原文件 try { File progressFile = new File(Environment.getExternalStorageDirectory(), threadId + ".txt"); //判断进度临时文件是否存在 if(progressFile.exists()){ FileInputStream fis = new FileInputStream(progressFile); BufferedReader br = new BufferedReader(new InputStreamReader(fis)); //从进度临时文件中读取出上一次下载的总进度,然后与原本的开始位置相加,得到新的开始位置 int lastProgress = Integer.parseInt(br.readLine()); startIndex += lastProgress; //把上次下载的进度显示至进度条 currentProgress += lastProgress; pb.setProgress(currentProgress); //发送消息,让主线程刷新文本进度 handler.sendEmptyMessage(1); fis.close(); } System.out.println("线程" + threadId + "的下载区间是:" + startIndex + "---" + endIndex); HttpURLConnection conn; URL url = new URL(path); conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); conn.setReadTimeout(5000); //设置本次http请求所请求的数据的区间 conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex); //请求部分数据,相应码是206 if(conn.getResponseCode() == 206){ //流里此时只有1/3原文件的数据 InputStream is = conn.getInputStream(); byte[] b = new byte[1024]; int len = 0; int total = 0; //拿到临时文件的输出流 File file = new File(Environment.getExternalStorageDirectory(), fileName); RandomAccessFile raf = new RandomAccessFile(file, "rwd"); //把文件的写入位置移动至startIndex raf.seek(startIndex); while((len = is.read(b)) != -1){ //每次读取流里数据之后,同步把数据写入临时文件 raf.write(b, 0, len); total += len; System.out.println("线程" + threadId + "下载了" + total); //每次读取流里数据之后,把本次读取的数据的长度显示至进度条 currentProgress += len; pb.setProgress(currentProgress); //发送消息,让主线程刷新文本进度 handler.sendEmptyMessage(1); //生成一个专门用来记录下载进度的临时文件 RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd"); //每次读取流里数据之后,同步把当前线程下载的总进度写入进度临时文件中 progressRaf.write((total + "").getBytes()); progressRaf.close(); } System.out.println("线程" + threadId + "下载完毕-------------------小志参上!"); raf.close(); finishedThread++; synchronized (path) { if(finishedThread == ThreadCount){ for (int i = 0; i < ThreadCount; i++) { File f = new File(Environment.getExternalStorageDirectory(), i + ".txt"); f.delete(); } finishedThread = 0; } } } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }
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