DownloadManager的使用

DownloadManager是系统开放给第三方应用使用的类，包含两个静态内部类DownloadManager.Query和DownloadManager.Request。DownloadManager.Request用来请求一个下载，DownloadManager.Query用来查询下载信息。具体使用代码如下：

 package com.example.administrator.mystudent.downloadManager;

 import android.app.Activity;
 import android.app.DownloadManager;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.database.Cursor;
 import android.net.Uri;
 import android.os.Environment;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.View;
 import android.widget.AdapterView;
 import android.widget.Button;
 import android.widget.TextView;
 import android.widget.Toast;

 import com.example.administrator.mystudent.R;

 import java.util.HashMap;
 import java.util.Map;

 public class DownLoadActivity extends Activity {
     private Button starButton;
     private Button stopButton;
     private Button dirButton;
     private TextView infoText;

     private DownloadManager downloader;
     private Uri uri;
     private long reference;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_down_load);

         initView();
     }

     private void initView() {
         starButton = (Button) findViewById(R.id.star);
         stopButton = (Button) findViewById(R.id.stop);
         dirButton = (Button) findViewById(R.id.dir);
         infoText= (TextView) findViewById(R.id.myText);

         starButton.setOnClickListener(new myButtonListener());
         stopButton.setOnClickListener(new myButtonListener());
         dirButton.setOnClickListener(new myButtonListener());
     }

     class myButtonListener implements View.OnClickListener {
         @Override
         public void onClick(View v) {
             switch (v.getId()) {
                 case R.id.star: {
                     //执行下载任务
                     downLoadManager();
                 }
                 break;
                 case R.id.stop: {
                     //停止下载
                     downloader.remove(reference);
                 }
                 break;
                 case R.id.dir: {
                     //获取存放地址
                     Map sDir=getMyFilesDir();
                     infoText.setText("downid:"+sDir.get("downid")
                             +"title:"+sDir.get("title")
                             +"statuss:"+sDir.get("statuss")
                             +"address:"+sDir.get("address")
                             +"status:"+sDir.get("status")
                     );
                 }
                 break;
             }
         }
     }

     /**
      * 获取下载的文件存贮路径
      * @return 文件路径
      */
     private Map getMyFilesDir() {
         Map<String, String> map = null;
         //创建查询对象
         DownloadManager.Query query=new DownloadManager.Query();
         //根据任务编号查询下载任务信息
         query.setFilterById(reference);

         Cursor cursor=downloader.query(query);
         while (cursor.moveToNext()){
             String downId= cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_ID));    //下载文件的id
             String title = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_TITLE)); //下载文件的题目
             String address = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI)); //下载的地址
             String statuss = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));   //状态
             String size= cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR)); //大小
             String sizeTotal = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES)); //总大小

             map = new HashMap<String, String>();
             map.put("downid", downId);
             map.put("title", title);
             map.put("statuss", statuss);
             map.put("address", address);
             map.put("status", sizeTotal+":"+size);
         }
         cursor.close();
         return map;
     }

     /**
      * DownloadManager的使用
      */
     private void downLoadManager() {
         //创建downLoadManager的管理器
         downloader = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
         //创建一个URI
         // uri = Uri.parse("http://biz.10039shop.com/download/leyt/leyt.apk");
         uri = Uri.parse("http://p1.ifengimg.com/a/2017_09/75dd25f878e8715_size66_w600_h363.jpg");
         //封装一个request对象
         DownloadManager.Request request = new DownloadManager.Request(uri);
         //设置文件必须在WIFI下下载
         request.setAllowedNetworkTypes(request.NETWORK_WIFI);

         //用于设置下载时时候在状态栏显示通知信息
         request.setNotificationVisibility(request.VISIBILITY_VISIBLE);
         //设置通知栏标题
         request.setTitle("百度下载");
         //设置Notification的message信息
         request.setDescription("图片正在下载");
         //用于设置漫游状态下是否可以下载
         request.setAllowedOverRoaming(false);
         //设置文件存放目录
         request.setDestinationInExternalFilesDir(this, Environment.DIRECTORY_DOWNLOADS, "myDownLoad");

         //发送request请求并返回一个下载ID(开始下载了)
         reference = downloader.enqueue(request);
         Log.e("开始下载", "下载的id是" + reference);

         //创建一个下载的广播,下载完成之后
         IntentFilter intentFilter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);

         BroadcastReceiver myReceiver = new BroadcastReceiver() {
             @Override
             public void onReceive(Context context, Intent intent) {
                 long referenceTo = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
                 if (referenceTo == reference) {
                     Log.e("结束下载", "下载完成" + referenceTo);
                     Toast.makeText(getApplicationContext(), "文件下载完成", Toast.LENGTH_SHORT).show();
                 }
             }
         };
         //注册广播
         registerReceiver(myReceiver, intentFilter);
     }
 }