android调用系统下载器下载文件

   在项目中使用到了在android端下载服务端的文件，之前使用的是http下载方式，现在想改成调用系统的下载器进行下载，实现步骤为：

  1.得到url：文件下载地址

  2.使用URL下载：

 (1)下载前先判断文件是否已经在下载，避免重复下载：

  

// 判断该文件是否在下载
	private boolean isDowning(String uri) {
		boolean flag = false;
		try {
			DownloadManager.Query query = new DownloadManager.Query();

			query.setFilterByStatus(DownloadManager.STATUS_RUNNING);
			if (downloadManager == null) {
				downloadManager = ((DownloadManager) this
						.getSystemService(Activity.DOWNLOAD_SERVICE));
			}
			Cursor c = downloadManager.query(query);
			String downingURI;
			while (c.moveToNext()) {
				downingURI = c.getString(c
						.getColumnIndex(DownloadManager.COLUMN_URI));
				if (downingURI.equalsIgnoreCase(uri)) {
					flag = true;
					break;
				}
			}
			if (c != null) {
				c.close();
			}
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return flag;
	}

  （2）如果未在下载则下载文件：

// 本地存储路径
Request request = new Request(Uri.parse(url));
// 在通知栏中显示
request.setShowRunningNotification(true);
request.setVisibleInDownloadsUi(true);
String dir ="tempFilrDir";//本地文件存储目录 相对路径
String fileName =  "悟空.mp3";//下载的文件名称

request.setDestinationInExternalPublicDir(dir, fileName);//文件存储路径 绝对路径
request.setTitle(fileName );//下载时在通知栏显示的文字

//downloadManager = ((DownloadManager) this.getSystemService(Activity.DOWNLOAD_SERVICE));

long downloadId = downloadManager.enqueue(request);//执行下载   
DownloadCompleteReceiver.mDownloadIDs.add(new Long(downloadId));// 
  DownloadCompleteReceiver下载完成的接收器，第//3步会讲到 
  
 
  
(3)接收完成的接收器
 
  
package com.bcts.appmanage.manage;
import java.util.ArrayList;
import android.app.DownloadManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

import com.bcts.appmanage.tools.Constant;

/**
 * 调用系统下载器下载文件
 *  
 */
public class DownloadCompleteReceiver extends BroadcastReceiver {
	public static final String TAG = "DownloadCompleteReceiver";

	public static ArrayList mDownloadIDs = new ArrayList();

	public String fileName;
	public  Handler mHandler;


	public  DownloadCompleteReceiver(Handler handler) {
		mHandler = handler ;
	}

	@Override
	public void onReceive(Context context, Intent intent) {
		if (intent.getAction().equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)) {
			long downId = intent.getLongExtra(
					DownloadManager.EXTRA_DOWNLOAD_ID, -1);
			//
			if (mDownloadIDs.contains(downId)) {
				// //////////////////////////////
				DownloadManager downloadManager = (DownloadManager) context
						.getSystemService(Context.DOWNLOAD_SERVICE);

				DownloadManager.Query query = new DownloadManager.Query();
				// query.setFilterByStatus(DownloadManager.STATUS_SUCCESSFUL);
				query.setFilterById(downId);
				Cursor c = downloadManager.query(query);
				if (c.moveToFirst()) {
					fileName = c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));
					Message m = new Message();
					m.obj = fileName;
					m.what = Constant.DOWNLOAD_FINISHED;
					mHandler.sendMessage(m);
					Log.i(TAG, "下载'" + fileName + "'完成");
				}else{
					Log.i(TAG, "下载'" + fileName + "'失败");
				}
				if (c != null) {
					c.close();
				}
				mDownloadIDs.remove(downId);

			}

		}
	}

}
 
  
(4)注册接收完成的广播
 
  
 
  
   
	downloadCompleteReceiver = new DownloadCompleteReceiver(mHandler);
		IntentFilter myIntentFilter = new IntentFilter();
		myIntentFilter.addAction(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
		// 注册广播
		registerReceiver(downloadCompleteReceiver, myIntentFilter);