DownloadManager

在androi中，volley适合小文件的获取和大并发，如果支持大文件的下载可以用Android原生的DownloadManager。DownloadManager默认支持多线程下载、断点续传等。

基础代码如下：

public class MainActivity extends Activity {

    private DownloadManager manager ;
    private DownloadCompleteReceiver receiver;
    private Button downBtn ;
    private Context mContext;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        //获取下载服务
        IntentFilter filter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
        receiver = new DownloadCompleteReceiver();
        registerReceiver(receiver, filter);

        downBtn = (Button)findViewById(R.id.button1);
        downBtn.setOnClickListener(new OnClickListener() {  

            public void onClick(View v) {
                //创建下载请求
                DownloadManager.Request request = new DownloadManager.Request(
                        Uri.parse("http://www.bz55.com/uploads/allimg/110807/2019341501-0.jpg"));

                request.setAllowedNetworkTypes(Request.NETWORK_WIFI);

                //定义notification提示
                request.setNotificationVisibility(Request.VISIBILITY_VISIBLE);
                request.setTitle("下载");
                request.setDescription("壁纸正在下载");
                //在onclick中无法直接通过this取到Context上下文
                request.setDestinationInExternalFilesDir(mContext, null, "test_download");
                manager =(DownloadManager)getSystemService(DOWNLOAD_SERVICE); 

                manager.enqueue(request);
            }
        });
    } 

    //接受下载完成后的intent
    class DownloadCompleteReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            if(intent.getAction().equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)){
                Toast.makeText(context, "download complete", Toast.LENGTH_SHORT).show();
            }
        }
    }  

    @Override
    protected void onDestroy() {
        if(receiver != null){
            unregisterReceiver(receiver);
        }
        super.onDestroy();
    }
}