使用Android自带DownloadManager下载文件

转自：http://blog.csdn.net/lixiang0522/article/details/7608310

 

SDK在API Level 9中加入了DownloadManager服务，可以将长时间的下载任务交给系统，完全由系统管理。

 

直接看实例代码：

package com.hebaijun.downloadtest;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import android.app.Activity;
import android.app.DownloadManager;
import android.app.DownloadManager.Request;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.webkit.MimeTypeMap;

public class DownloadTestActivity extends Activity {
    private DownloadManager downloadManager;
    private SharedPreferences prefs;
    private static final String DL_ID = "downloadId";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
        prefs = PreferenceManager.getDefaultSharedPreferences(this);
    }
    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        unregisterReceiver(receiver);
    }
    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        if(!prefs.contains(DL_ID)) {
            String url = "http://10.0.2.2/android/film/G3.mp4";
            //开始下载
            Uri resource = Uri.parse(encodeGB(url));
            DownloadManager.Request request = new DownloadManager.Request(resource);
            request.setAllowedNetworkTypes(Request.NETWORK_MOBILE | Request.NETWORK_WIFI);
            request.setAllowedOverRoaming(false);
            //设置文件类型
            MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
            String mimeString = mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(url));
            request.setMimeType(mimeString);
            //在通知栏中显示
            request.setShowRunningNotification(true);
            request.setVisibleInDownloadsUi(true);
            //sdcard的目录下的download文件夹
            request.setDestinationInExternalPublicDir("/download/", "G3.mp4");
            request.setTitle("移动G3广告");
            long id = downloadManager.enqueue(request);
            //保存id
            prefs.edit().putLong(DL_ID, id).commit();
        } else {
            //下载已经开始，检查状态
            queryDownloadStatus();
        }

        registerReceiver(receiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
    }

    /**
     * 如果服务器不支持中文路径的情况下需要转换url的编码。
     * @param string
     * @return
     */
    public String encodeGB(String string)
    {
        //转换中文编码
        String split[] = string.split("/");
        for (int i = 1; i < split.length; i++) {
            try {
                split[i] = URLEncoder.encode(split[i], "GB2312");
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            split[0] = split[0]+"/"+split[i];
        }
        split[0] = split[0].replaceAll("\\+", "%20");//处理空格
        return split[0];
    }

    private BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            //这里可以取得下载的id，这样就可以知道哪个文件下载完成了。适用与多个下载任务的监听
            Log.v("intent", ""+intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0));
            queryDownloadStatus();
        }
    };

    private void queryDownloadStatus() {
        DownloadManager.Query query = new DownloadManager.Query();
        query.setFilterById(prefs.getLong(DL_ID, 0));
        Cursor c = downloadManager.query(query);
        if(c.moveToFirst()) {
            int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
            switch(status) {
            case DownloadManager.STATUS_PAUSED:
                Log.v("down", "STATUS_PAUSED");
            case DownloadManager.STATUS_PENDING:
                Log.v("down", "STATUS_PENDING");
            case DownloadManager.STATUS_RUNNING:
                //正在下载，不做任何事情
                Log.v("down", "STATUS_RUNNING");
                break;
            case DownloadManager.STATUS_SUCCESSFUL:
                //完成
                Log.v("down", "下载完成");
                break;
            case DownloadManager.STATUS_FAILED:
                //清除已下载的内容，重新下载
                Log.v("down", "STATUS_FAILED");
                downloadManager.remove(prefs.getLong(DL_ID, 0));
                prefs.edit().clear().commit();
                break;
            }
        }
    }
}

最后需要的权限是：

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

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

如果需要隐藏下载工具的提示和显示，修改代码：

request.setShowRunningNotification(false);

request.setVisibleInDownloadsUi(false);

加入下面的权限：

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