Android有進度條的下載圖片并且顯示圖片

   采用progressBar控件寫一個有進度條的下載文件例子！下面的代碼就是下載一個圖片，并且把圖片顯示出來的代碼：

layout文件布局很簡單：

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


<Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@+id/bt"
    android:text="開始下載文件" />

<ProgressBar
    android:id="@+id/pb"
    android:layout_width="fill_parent"
    style="?android:attr/progressBarStyleHorizontal"
    android:layout_height="wrap_content" />
<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/img"/>

</LinearLayout></pre> 
  
 一個文件工具類： 
  
package com.spring.sky.download;

import java.io.File;
import android.content.Context;
import android.os.Environment;
import android.util.Log;
/**

文件工具類
@author spring sky
Email:vipa1888@163.com
QQ:840950105
name:石明政
/
public class FileUtil {
 /**

檢驗SDcard狀態
@return boolean
*/
public static boolean checkSDCard()
{
 if(android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
 {
 return true;

 }else{
 return false;

 }
}
/**
保存文件文件到目錄
@param context
@return  文件保存的目錄
*/
public static String setMkdir(Context context)
{
 String filePath;
 if(checkSDCard())
 {
 filePath = Environment.getExternalStorageDirectory()+File.separator+"myfile";

 }else{
 filePath = context.getCacheDir().getAbsolutePath()+File.separator+"myfile";

 }
 File file = new File(filePath);
 if(!file.exists())
 {
 boolean b = file.mkdirs();
 Log.e("file", "文件不存在  創建文件    "+b);

 }else{
 Log.e("file", "文件存在");

 }
 return filePath;
}
}</pre>下面就是界面上的邏輯處理: 
package com.spring.sky.download;



import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
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.Toast;
/**

文件下載界面
@author spring sky
Email:vipa1888@163.com
QQ:840950105
name:石明政
/
public class IndexActivity extends Activity implements OnClickListener{
 private static final int DOWNLOAD_PREPARE = 0;
 private static final int DOWNLOAD_WORK = 1;
 private static final int DOWNLOAD_OK = 2;
 private static final int DOWNLOAD_ERROR =3;
 private static final String TAG = "IndexActivity";
 private Button bt ;
 private ProgressBar pb;
 private ImageView img;
 /**

需要下載的文件
注意：在模擬器上面使用無法解析有域名的主機
*/
private String url = "http://61.155.165.32/shuixiyue/pic/item/f141247490d0e96fb251b963.jpg&quot;;
@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 bt = (Button) this.findViewById(R.id.bt);
 bt.setOnClickListener(this);
 pb = (ProgressBar) this.findViewById(R.id.pb);
 pb.setVisibility(ProgressBar.INVISIBLE);
 img =(ImageView) this.findViewById(R.id.img);
}
/**

按鈕點擊事件
*/
@Override
public void onClick(View v) {
 switch (v.getId()) {
 case R.id.bt:
 Toast.makeText(this, "開始下載文件", Toast.LENGTH_SHORT).show();
 new Thread(){
     @Override
     public void run() {
         downloadFile();
         super.run();
     }
 }.start();
 break;

 }
}
/**
文件下載
*/
private void downloadFile()
{
 try {
 URL u = new URL(url);
 URLConnection conn = u.openConnection();
 conn.connect();
 InputStream is = conn.getInputStream();
 fileSize = conn.getContentLength();
 if(fileSize<1||is==null)
 {
     sendMessage(DOWNLOAD_ERROR);
 }else{
     sendMessage(DOWNLOAD_PREPARE);
     FileOutputStream fos = new FileOutputStream(getPath());
     byte[] bytes = new byte[1024];
     int len = -1;
     while((len = is.read(bytes))!=-1)
     {
         fos.write(bytes, 0, len);
         downloadSize+=len;
         sendMessage(DOWNLOAD_WORK);
     }
     sendMessage(DOWNLOAD_OK);
     is.close();
     fos.close();
 }

 } catch (Exception e) {
 sendMessage(DOWNLOAD_ERROR);
 e.printStackTrace();

 } 
}
/**
文件一共的大小
*/
int fileSize = 0;
/**
已經下載的大小
*/
int downloadSize = 0;
/**
handler處理消息
*/
private Handler handler = new Handler(){
@Override
 public void handleMessage(Message msg) {

 switch (msg.what) {
 case DOWNLOAD_PREPARE:
     Toast.makeText(IndexActivity.this, "下載準備", Toast.LENGTH_SHORT).show();
     pb.setVisibility(ProgressBar.VISIBLE);
     Log.e(TAG, "一共:"+fileSize);
     pb.setMax(fileSize);
     break;
 case DOWNLOAD_WORK:
     Log.e(TAG, "已下載:"+downloadSize);
     pb.setProgress(downloadSize);
     int res = downloadSize*100/fileSize;
     bt.setText("已下載："+res+"%");
     break;
 case DOWNLOAD_OK:
     try {
         if(getPath().endsWith(".jpg")||getPath().endsWith(".png")){
             FileInputStream fis = new FileInputStream(getPath());
             img.setImageBitmap(BitmapFactory.decodeStream(fis));
         }
         downloadSize = 0;
         fileSize = 0;
     } catch (FileNotFoundException e) {
         e.printStackTrace();
     } catch (IOException e) {
         e.printStackTrace();
     }
     Toast.makeText(IndexActivity.this, "下載完成", Toast.LENGTH_SHORT).show();
     break;
 case DOWNLOAD_ERROR:
     Toast.makeText(IndexActivity.this, "下載出錯", Toast.LENGTH_SHORT).show();
     break;
 }
 super.handleMessage(msg);

}
};
/**

得到文件的保存路徑
@return
@throws IOException
*/
private String getPath() throws IOException
{
 String path = FileUtil.setMkdir(this)+File.separator+url.substring(url.lastIndexOf("/")+1);
 return path;
}
/**
給hand發送消息
@param what
*/
private void sendMessage(int what)
{
 Message m = new Message();
 m.what = what;
 handler.sendMessage(m);
}
}</pre> 
 轉自： 
http://blog.csdn.net/vipa1888/article/details/7208956