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;

/**
 * 原生程式碼下載檔案例項
 */
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();

            }

        });
    }

    /**
     * 從網路Url中下載檔案
     *
     * @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();
        //設定超時間為3秒
        conn.setConnectTimeout(3 * 1000);
        //防止遮蔽程式抓取而返回403錯誤
        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

        //得到輸入流
        InputStream inputStream = conn.getInputStream();
        //獲取自己陣列
        byte[] getData = readInputStream(inputStream);

        //檔案儲存位置
        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");
    }

    /**
     * 從輸入流中獲取位元組陣列
     *
     * @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();
    }

}