android 之文件下载

首先，我们使用IO对文件进行下载操作，把下载到的文件保存到sdCard目录下。前提是保证有sdCard。

看代码吧：

ImageService.java

package com.hkrt.action;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.text.SimpleDateFormat;import java.util.Date;public class ImageService {//从互联网上读取图片http://hiphotos.baidu.com/huyangdiy/pic/item/7509b40db709fce9d0581bfc.jpgpublic static byte[] getImage(String path) throws Throwable{URL url = new URL(path);HttpURLConnection  conn = (HttpURLConnection)url.openConnection();conn.setReadTimeout(5*1000);if(conn.getResponseCode()==HttpURLConnection.HTTP_OK){InputStream is  = conn.getInputStream();return readIS(is);}else{throw new Exception("请求路径错误");}}public  static byte []  readIS(InputStream is) throws IOException{ByteArrayOutputStream bos = new ByteArrayOutputStream();byte [] buff = new byte[1024];int length=0;while((length =is.read(buff))!=-1){bos.write(buff, 0, length);}return bos.toByteArray();}/** * @param path 资源路径 * @return   资源文件流 * @throws Throwable */public static InputStream getInputStream(String path) throws Throwable{URL url = new URL(path);HttpURLConnection  conn = (HttpURLConnection)url.openConnection();conn.setReadTimeout(5*1000);if(conn.getResponseCode()==HttpURLConnection.HTTP_OK){InputStream is  = conn.getInputStream();return is;}return null;}/**对下载文件以时间重命名*/public static String getDateTime(){return new SimpleDateFormat("yyyy-MM-dd hh-MM-ss").format(new Date()).toString();}}

ImageViewActivity.java

package com.hkrt.action;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.ImageView;import android.widget.Toast;/** * 点击按钮从网下查看图片 * @author Administrator * */public class ImageViewActivity extends Activity {private static final String TAG="ImageViewActivity";    private EditText urlEdt;//文件路径    private ImageView imageView;//页面中展示的图片    private Button downLoadButton ;//下载按钮@Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        urlEdt=(EditText)this.findViewById(R.id.path);        imageView =(ImageView)this.findViewById(R.id.image);        downLoadButton  =(Button)this.findViewById(R.id.button);        downLoadButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {String imagePath = urlEdt.getText().toString();try {byte [] imageByte = ImageService.getImage(imagePath);Bitmap bm = BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length);imageView.setImageBitmap(bm);String imageSuffix = imagePath.substring(imagePath.lastIndexOf("."), imagePath.length());downLoadImage(imagePath,ImageService.getDateTime()+imageSuffix );//下载图片} catch (Throwable e) {Log.i(TAG, e.toString());Toast.makeText(getApplicationContext(), "图片儿获取失败", Toast.LENGTH_SHORT).show();}}});    }/**下载文件到sd卡上*/public void downLoadImage(String path,String fileName){ if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){              File sdCardDir = Environment.getExternalStorageDirectory();//获取到文件的存储路径            InputStream is=null ;            try {                          File dest =new File(sdCardDir.getCanonicalPath()+File.separator+"imageMe");               is = ImageService.getInputStream(path);              if(!dest.exists()){             dest.mkdirs();              }             OutputStream output = new FileOutputStream(dest+File.separator+fileName);                   byte[] buffer = new byte[8192];                   while((is.read(buffer)) != -1){                       output.write(buffer);                   }                   output.flush();                  System.out.println("下载成功");} catch (Throwable e) {e.printStackTrace();}finally{if(is!=null){try {is.close();} catch (IOException e) {e.printStackTrace();}}}    }}}

效果图：

注：把下载的文件导出去，使用文件预览打不开，原始不明。换其他的打开方式。
以上方法是实现了图片显示和下载的功能，但下载的时候是在主线程中执行的，这人时候就会有问题了。UI线程执行代码的速度最好不要超过10秒。

这个时候，做下载时，我们应该独立开启一个线程做下载功能处理。

主要实现代码：

在点击获取图片是开启一个新的线程：

Thread loginThread = new Thread(new DownloadThread());  loginThread.start();

线程的新方法实现下载，并把下载成功与否返回给handle 。

private class DownloadThread implements Runnable{@Overridepublic void run() {String imageSuffix = imagePath.substring(imagePath.lastIndexOf("."), imagePath.length());boolean down =downLoadImage(imagePath,ImageService.getDateTime()+imageSuffix );//下载图片Message message = new Message();Bundle bun = new Bundle();bun.putBoolean("downLoadState", down);message.setData(bun);downLoadHandler.sendMessage(message);}}

返回handle处理结果信息并通知下载成功与否：

 downLoadHandler  = new Handler(){@Overridepublic void handleMessage(Message msg) {Bundle bun = msg.getData();boolean downState = (Boolean)bun.getBoolean("downLoadState");if(downState){Intent intent = new Intent(ImageViewActivity.this,OtherActivity.class);PendingIntent contentIntent = PendingIntent.getActivity(ImageViewActivity.this, 0, intent, 0);Notification notify = new Notification();notify.icon=R.drawable.icon1;notify.tickerText="启动otherActivity通知";notify.when=System.currentTimeMillis();notify.defaults=Notification.DEFAULT_SOUND;notify.defaults=Notification.DEFAULT_ALL;notify.setLatestEventInfo(ImageViewActivity.this, "普通通知", "点击查看", contentIntent);NotificationManager manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);manager.notify(0, notify);}else{Toast.makeText(getApplicationContext(), "图片儿下载失败", Toast.LENGTH_SHORT).show();}super.handleMessage(msg);}                };

同时需要添加通知震动的权限：

 

  <uses-permission android:name="android.permission.VIBRATE" />