Android根据URL下载文件保存到SD卡

package org.hpg.weather.download;import android.os.Environment;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Button;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.io.OutputStream;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;public class MainActivity extends ActionBarActivity {    private static final String TAG = "MainActivity";    String downloadUrl = "http://down.androidonline.net/upload/apkoldown/xiaomibianqian.apk";    String picUrl ="http://img01.mifile.cn/images/accs/xmjsb_11.jpg";    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button) findViewById(R.id.download);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                new Thread(new Runnable() {                    @Override                    public void run() {                        download();                    }                }).start();            }        });    }    //下载具体操作    private void download() {        try {            URL url = new URL(downloadUrl);            //打开连接            URLConnection conn = url.openConnection();            //打开输入流            InputStream is = conn.getInputStream();            //获得长度            int contentLength = conn.getContentLength();            Log.e(TAG, "contentLength = " + contentLength);            //创建文件夹 MyDownLoad，在存储卡下            String dirName = Environment.getExternalStorageDirectory() + "/MyDownLoad/";            File file = new File(dirName);            //不存在创建            if (!file.exists()) {                file.mkdir();            }            //下载后的文件名            String fileName = dirName + "xiaomibianqian.apk";            File file1 = new File(fileName);            if (file1.exists()) {                file1.delete();            }            //创建字节流            byte[] bs = new byte[1024];            int len;            OutputStream os = new FileOutputStream(fileName);            //写数据            while ((len = is.read(bs)) != -1) {                os.write(bs, 0, len);            }            //完成后关闭流            Log.e(TAG, "download-finish");            os.close();            is.close();        } catch (Exception e) {            e.printStackTrace();        }    }}
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