Android文件下载进度条的实现代码

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文件下载进度条控制（就是为了高清壁纸加个进度条），自己研究了好久，但是进度条只能显示缓存写入文件的进度，不能显示下载进度。找了好久，终于找到一段用的代码，所以记录下来，大家分享

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    ><TextView  android:id="@+id/tv"    android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:text=""    /><ProgressBar android:id="@+id/down_pb" android:layout_width="fill_parent"     android:layout_height="wrap_content"    android:max="100"    style="?android:attr/progressBarStyleHorizontal" mce_style="?android:attr/progressBarStyleHorizontal"/></LinearLayout>

package com.pocketdigi.download;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.URL;import java.net.URLConnection;import org.apache.http.client.ClientProtocolException;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;import android.widget.ProgressBar;import android.widget.TextView;import android.widget.Toast;public class main extends Activity {    /** Called when the activity is first created. */ ProgressBar pb; TextView tv; int   fileSize; int   downLoadFileSize; String fileEx,fileNa,filename; private Handler handler = new Handler()   {     @Override     public void handleMessage(Message msg)     {//定义一个Handler，用于处理下载线程与UI间通讯       if (!Thread.currentThread().isInterrupted())       {         switch (msg.what)         {           case 0:             pb.setMax(fileSize);           case 1:             pb.setProgress(downLoadFileSize);             int result = downLoadFileSize * 100 / fileSize;             tv.setText(result + "%");             break;           case 2:             Toast.makeText(main.this, "文件下载完成", 1).show();             break;           case -1:             String error = msg.getData().getString("error");             Toast.makeText(main.this, error, 1).show();             break;         }       }       super.handleMessage(msg);     }   };    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        pb=(ProgressBar)findViewById(R.id.down_pb);        tv=(TextView)findViewById(R.id.tv);        new Thread(){         public void run(){          try {     down_file("http://wallpaper.pocketdigi.com/upload/1/bigImage/1284565196.jpg","/sdcard/");     //下载文件，参数：第一个URL，第二个存放路径    } catch (ClientProtocolException e) {     // TODO Auto-generated catch block     e.printStackTrace();    } catch (IOException e) {     // TODO Auto-generated catch block     e.printStackTrace();    }         }        }.start();    }    public void down_file(String url,String path) throws IOException{     //下载函数         filename=url.substring(url.lastIndexOf("/") + 1);     //获取文件名     URL myURL = new URL(url);     URLConnection conn = myURL.openConnection();     conn.connect();     InputStream is = conn.getInputStream();     this.fileSize = conn.getContentLength();//根据响应获取文件大小     if (this.fileSize <= 0) throw new RuntimeException("无法获知文件大小 ");     if (is == null) throw new RuntimeException("stream is null");     FileOutputStream fos = new FileOutputStream(path+filename);     //把数据存入路径+文件名     byte buf[] = new byte[1024];     downLoadFileSize = 0;     sendMsg(0);     do       {      //循环读取         int numread = is.read(buf);         if (numread == -1)         {           break;         }         fos.write(buf, 0, numread);         downLoadFileSize += numread;         sendMsg(1);//更新进度条       } while (true);     sendMsg(2);//通知下载完成     try       {         is.close();       } catch (Exception ex)       {         Log.e("tag", "error: " + ex.getMessage(), ex);       }    } private void sendMsg(int flag) {     Message msg = new Message();     msg.what = flag;     handler.sendMessage(msg); }  }

大家看了以后就应该明白了，上面写的是用一个循环来完成的这些事情，byte buf[] = new byte[1024];这句话中大家一定要写1024，这个可不能改变呀。sendMsg(0);这句的括号里写的是0，这个也要记得，是0而不是1.

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