android自带下载工具Downloadmanager

代码如下：

package jun.xiazaid;

import android.app.DownloadManager;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import java.io.File;

public class Main2Activity extends AppCompatActivity implements View.OnClickListener {

    private Button xiazai;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        initView();
    }

    private void initView() {
        xiazai = (Button) findViewById(R.id.xiazai);

        xiazai.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.xiazai:
                String downloadUrl = "http://apk.hiapk.com/appdown/net.csdn.csdnplus";
                String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/demo.apk";
                down(downloadUrl,path);

                String d1 = "http://4493bz.1985t.com/uploads/allimg/150127/4-15012G52133.jpg";
                String p1 = Environment.getExternalStorageDirectory().getAbsolutePath() + "/demo1.jpg";
                down(d1,p1);

                String d2 = "http://pic6.huitu.com/res/20130116/84481_20130116142820494200_1.jpg";
                String p2 = Environment.getExternalStorageDirectory().getAbsolutePath() + "/demo2.jpg";
                down(d2,p2);

                String d3 = "http://4493bz.1985t.com/uploads/allimg/150127/4-15012G52133.jpg";
                String p3 = Environment.getExternalStorageDirectory().getAbsolutePath() + "/demo3.jpg";
                down(d3,p3);
                break;
        }
    }

    public void down(String url,String path){

        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
        File saveFile = new File(path);
        if (saveFile.exists()) {
            //删除已存在的文件
            saveFile.delete();
        }
        request.setDestinationUri(Uri.fromFile(saveFile));
        DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
        long downloadId = manager.enqueue(request);

    }
}