Android快速实现断点续传的方法

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

<&＃63;xml version="1.0" encoding="utf-8"&＃63;>



  
  

package com.five.fashion.duandianxuchuan;

import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
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 com.loopj.android.http.HttpGet;

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.HttpHead;
import cz.msebera.android.httpclient.impl.client.DefaultHttpClient;


public class MainActivity extends AppCompatActivity {
  protected static final String TAG = "OtherActivity";
  //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";
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //找到控件
    pb = (ProgressBar) findViewById(R.id.pb);
    tv_info = (TextView) findViewById(R.id.tv_info);
    bt_download = (Button) findViewById(R.id.bt_download);
    bt_pause = (Button) findViewById(R.id.bt_pause);
    //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