Android中设置进度条来监督下载进程

昨天做了一个Android中利用进度条来监督下载一个图片或者一首歌曲的进度：

简单的界面，但是可以实现那个功能：

这是main.xml中的代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

 <TextView
     android:id="@+id/txt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="#FFFF37"
        android:text="下载进度" />

    <Button
        android:id="@+id/downImg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/button_style"
        android:text="开始下载图片" />

    <FrameLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >

        <ImageView
            android:id="@+id/imgView"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:contentDescription="@string/app_name" />

        <ProgressBar
            android:id="@+id/progressBar"
            android:layout_width="fill_parent"
            style="?android:attr/progressBarStyleHorizontal"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:visibility="invisible" />
    </FrameLayout>

</LinearLayout>

这里是drawable里面去实现button点击的按钮样式的：

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
        <item android:state_pressed="true">
        <shape>
            <gradient android:startColor="#0d76e1" android:endColor="#0d76e1"
                android:angle="270" />
            <stroke android:width="1dip" android:color="#f403c9" />
            <corners android:radius="2dp" />
            <padding android:left="10dp" android:top="10dp"
                android:right="10dp" android:bottom="10dp" />
        </shape>
    </item>
 
    <item android:state_focused="true">
        <shape>
            <gradient android:startColor="#ffc2b7" android:endColor="#ffc2b7"
                android:angle="270" />
            <stroke android:width="1dip" android:color="#f403c9" />
            <corners android:radius="2dp" />
            <padding android:left="10dp" android:top="10dp"
                android:right="10dp" android:bottom="10dp" />
        </shape>
    </item>
 
    <item>
        <shape>
            <gradient android:startColor="#000000" android:endColor="#ffffff"
                android:angle="180" />
            <stroke android:width="1dip" android:color="#f403c9" />
            <corners android:radius="5dip" />
            <padding android:left="10dp" android:top="10dp"
                android:right="10dp" android:bottom="10dp" />
        </shape>
    </item>

</selector>

接下来的这个就是实现其功能的主要代码：.java文件

package cn.android.app.hsd;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class Chapter_11_URL_exampleActivity extends Activity implements OnClickListener { 
 // 声明视图上的各个对象
 private TextView txtView;
 private Button downImg;
 private ImageView imgView;
 // 定义一个ProgressBar控件，用于显示下载的进度
 private ProgressBar progressBar;
 private Bitmap bitmap;
 // 定义下载任务的状态，下载中，下载完成
 private static final int LOADING = 1;
 private static final int END = 2;
 //初始化进度条的最大值和最小值
 int maxSize = 0;
 int nowSize = 0;

 Handler handler;
 // 把图片写入到sd卡中，所以这里我们要定义一个路径

 private static final String SDCARD = "mnt/sdcard/";
 private String fileName = "networkImg.jpg";

//声明一个文件，待会用于存储
 File file;
 //设置图片的url，这里的url是在网上随便找到一张图片，然后点击起链接
  String imgHttp1 = "http://c.hiphotos.baidu.com/image/w%3D2048/sign=f1e49b68aa64034f0fcdc5069bfb7831/060828381f30e9240286c9844d086e061d95f761.jpg";
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

//然后将这些控件都实例化

  txtView = (TextView) findViewById(R.id.txt);
  downImg = (Button) findViewById(R.id.downImg);

//将按钮控件实现监听

  downImg.setOnClickListener(this);
  imgView = (ImageView) findViewById(R.id.imgView);
  progressBar = (ProgressBar) findViewById(R.id.progressBar);

//注意这里我们要涉及到更新ui界面，我们不能直接去更新，这就是java与android的区别，所以，我们要记住用handler

  handler = new Handler() {
   @Override
   public void handleMessage(Message msg) {
    if (null != progressBar) {
     // 设置进度条最大值
     progressBar.setMax(maxSize);
     // 当前已经下载的值
     nowSize += msg.getData().getInt("loadingSize");
     // 设置进度条的当前进度值
     progressBar.setProgress(nowSize);
     if (msg.what == LOADING) {
      // 显示已经下载的值（这里会有一点计算）
      txtView.setText("已下载：" + (nowSize*100)/maxSize  + "%");

      Log.e("Chapter_11_URL_exampleActivity", "正在下载："+ nowSize);
     }

     if (msg.what == END) {
      // 下载完成后隐藏进度条
      progressBar.setVisibility(View.INVISIBLE);
      // 显示图片
      imgView.setImageBitmap(bitmap);
      // 将图片保存到sdcard中
      saveImg(SDCARD + fileName, bitmap);
      // 结束当前线程
      Thread.currentThread().interrupt();
     }
    }
   }
  };
 }

//实现其点击事件

 @Override
 public void onClick(View paramView) {
  // 首先清空图片和进度条
  if (null != bitmap) {
   imgView.setImageBitmap(null);
   nowSize = 0;
   progressBar.setProgress(0);
   txtView.setText("即将下载......");
  }

  // 1、显示进度条
  progressBar.setVisibility(View.VISIBLE);

  // 2、开始下载
  new MyThread(imgHttp1).start();
 }

 // 保存图片方法
 public void saveImg(String fullPath, Bitmap bitmap) {
  File file = new File(fullPath);
  if (file.exists()) {
   file.delete();
  } else if (!file.exists()) {
   try {
    file.createNewFile();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }

  try {
   FileOutputStream fos = new FileOutputStream(file);
   boolean isSaved = bitmap.compress(Bitmap.CompressFormat.JPEG, 100,fos);

   if (isSaved) {
    fos.flush();
    fos.close();
   }
   System.out.println("文件保存成功!");
  } catch (FileNotFoundException e) {
   System.out.println("保存失败(FileNotFoundException)");
   e.printStackTrace();
  } catch (IOException e) {
   System.out.println("保存失败(IOException)");
   e.printStackTrace();
  }

 }

 class MyThread extends Thread {  
  String httpImg;
  //定义构造方法用来接收图片
  public MyThread(String httpImg) {
   this.httpImg = httpImg;
  }

  @Override
  public void run() {
   //(字节数组流)捕获内存缓冲区的数据，转换成字节数组
   ByteArrayOutputStream bos = new ByteArrayOutputStream();

   try {
    // 实例化URL对象，指定资源(图片)下载的地址
    URL url = new URL(httpImg);
    HttpURLConnection con = (HttpURLConnection) url
      .openConnection();
    con.setDoInput(true);
    con.connect();
    InputStream is = con.getInputStream();

    // 获取文件的大小
    maxSize = con.getContentLength();
    byte[] buffer = new byte[1024];
    int len = -1;
    while ((len = is.read(buffer)) != -1) {
     bos.write(buffer, 0, len);
     bos.flush();
     // 发送消息
     Message msg = new Message();
     msg.what = LOADING;
     Bundle bundle = new Bundle();
     bundle.putInt("loadingSize", len);
     msg.setData(bundle);
     Thread.sleep(1);//方法休眠20
     handler.sendMessage(msg);
    }

    // 关闭输入流
    is.close();
    // 关闭连接
    con.disconnect();

    byte[] imgBytes = bos.toByteArray();
    bitmap = BitmapFactory.decodeByteArray(imgBytes, 0,imgBytes.length);

    // 下载结束后发送消息
    Message msg = new Message();
    msg.what = END;
    handler.sendMessage(msg);
   } catch (MalformedURLException e) {
    e.printStackTrace();
   } catch (IOException e) {
    e.printStackTrace();
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
  }
 }
 
}