Android快速实现断点续传的方法

本文实例为大家分享了Android快速实现断点续传的具体代码，供大家参考，具体内容如下

1.导入依赖

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

2.导入权限

3.布局文件

4.主要代码

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 < 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();
      }
    }
    bt_download.setonClickListener(new View.onClickListener() {
      @Override
      public void onClick(View v) {
 download(v);
      }
    });
    bt_pause.setonClickListener(new View.onClickListener() {
      @Override
      public void onClick(View v) {
 pause(v);
      }
    });
  }
  //暂停
  private boolean flag = false;//是否在下载

  public void pause(View v){
    flag = false;
    bt_download.setEnabled(true);
    bt_pause.setEnabled(false);
  }

  //下载
  public void download(View v){
    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

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。