Android学习之使用HttpURLConnection下载文件

package com.example.administrator.myapplication;import android.os.Bundle;import android.os.Environment;import android.support.v7.app.ActionBarActivity;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.ImageView;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;/** * 原生代码下载文件实例 */public class MainActivity extends ActionBarActivity {    private ImageView imageView;    private EditText editText;    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        imageView = (ImageView) findViewById(R.id.imageView);        editText = (EditText) findViewById(R.id.editText);        button = (Button) findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                final String path = Environment.getExternalStorageDirectory().getPath() + "/AAAAImg/";                new Thread(new Runnable() {                    @Override                    public void run() {                        try {                            downLoadFromUrl(editText.getText().toString(), "123.jpg", path);                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                }).start();            }        });    }    /**     * 从网络Url中下载文件     *     * @param urlStr     * @param fileName     * @param savePath     * @throws IOException     */    public static void downLoadFromUrl(String urlStr, String fileName, String savePath) throws IOException {        URL url = new URL(urlStr);        HttpURLConnection conn = (HttpURLConnection) url.openConnection();        //设置超时间为3秒        conn.setConnectTimeout(3 * 1000);        //防止屏蔽程序抓取而返回403错误        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");        //得到输入流        InputStream inputStream = conn.getInputStream();        //获取自己数组        byte[] getData = readInputStream(inputStream);        //文件保存位置        File saveDir = new File(savePath);        if (!saveDir.exists()) {            saveDir.mkdir();        }        File file = new File(saveDir + File.separator + fileName);        FileOutputStream fos = new FileOutputStream(file);        fos.write(getData);        if (fos != null) {            fos.close();        }        if (inputStream != null) {            inputStream.close();        }        System.out.println("info:" + url + " download success");    }    /**     * 从输入流中获取字节数组     *     * @param inputStream     * @return     * @throws IOException     */    public static byte[] readInputStream(InputStream inputStream) throws IOException {        byte[] buffer = new byte[1024];        int len = 0;        ByteArrayOutputStream bos = new ByteArrayOutputStream();        while ((len = inputStream.read(buffer)) != -1) {            bos.write(buffer, 0, len);        }        bos.close();        return bos.toByteArray();    }}
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