android有进度条的下载图片并且显示图片

       最近工作不忙，感觉对progressBar不熟悉，所以决定写一个有进度条的下载文件例子！下面的代码就是我写的下载一个图片，并且把图片显示出来的代码：

layout文件布局很简单：

<?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" >

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/bt"
        android:text="开始下载文件" />

    <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>

一个文件工具类：

package com.spring.sky.download;

import java.io.File;

import android.content.Context;
import android.os.Environment;
import android.util.Log;
/**
 * 文件工具类
 * @author spring sky
 * Email:vipa1888@163.com
 * QQ:840950105
 * name:石明政
 *
 */
public class FileUtil {
	/**
	 * 检验SDcard状态
	 * @return boolean
	 */
	public static boolean checkSDCard()
	{
		if(android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
		{
			return true;
		}else{
			return false;
		}
	}
	/**
	 * 保存文件文件到目录
	 * @param context
	 * @return  文件保存的目录
	 */
	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  创建文件    "+b);
		}else{
			Log.e("file", "文件存在");
		}
		return filePath;
	}
}

 

下面就是界面上的逻辑处理:

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;
/**
 * 文件下载界面
 * @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;
	/**
	 * 需要下载的文件
	 * 注意：在模拟器上面使用无法解析有域名的主机
	 */
	private String url = "http://61.155.165.32/shuixiyue/pic/item/f141247490d0e96fb251b963.jpg";
	@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);
	}
	
	/**
	 * 按钮点击事件
	 */
	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.bt:
			Toast.makeText(this, "开始下载文件", Toast.LENGTH_SHORT).show();
			new Thread(){
				@Override
				public void run() {
					downloadFile();
					super.run();
				}
			}.start();
			break;
		}
	}
	/**
	 * 文件下载
	 */
	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;
	/**
	 * 已经下载的大小
	 */
	int downloadSize = 0;
	/**
	 * handler处理消息
	 */
	private Handler handler = new Handler(){

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case DOWNLOAD_PREPARE:
				Toast.makeText(IndexActivity.this, "下载准备", Toast.LENGTH_SHORT).show();
				pb.setVisibility(ProgressBar.VISIBLE);
				Log.e(TAG, "一共:"+fileSize);
				pb.setMax(fileSize);
				break;
			case DOWNLOAD_WORK:
				Log.e(TAG, "已下载:"+downloadSize);
				pb.setProgress(downloadSize);
				int res = downloadSize*100/fileSize;
				bt.setText("已下载："+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, "下载完成", Toast.LENGTH_SHORT).show();
				break;
			case DOWNLOAD_ERROR:
				Toast.makeText(IndexActivity.this, "下载出错", Toast.LENGTH_SHORT).show();
				break;
			}
			super.handleMessage(msg);
		}
	};
	/**
	 * 得到文件的保存路径
	 * @return
	 * @throws IOException
	 */
	private String getPath() throws IOException
	{
		String path = FileUtil.setMkdir(this)+File.separator+url.substring(url.lastIndexOf("/")+1);
		return path;
	}
	/**
	 * 给hand发送消息
	 * @param what
	 */
	private void sendMessage(int what)
	{
		Message m = new Message();
		m.what = what;
		handler.sendMessage(m);
	}
}

以上就是一个文件下载的完整代码，有需要这方面的朋友可以直接拷贝使用了！如果使用过程中有问题，可以联系我！

一位朋友提醒我了，这个下载过程需要两个权限，不然对新手来说，很困惑的！具体的权限如下：

 

<!-- Internet权限 -->
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<!--可访问SD卡-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

 具体的代码下载地址：http://download.csdn.net/detail/vipa1888/4028594    以后我提倡代码共享，也不会要积分的！我准备修改不要积分的  修改不了！请大家谅解！