HttpUrlConnection的应用

一、什么是HttpUrlConnection

HttpUrlConnection是java的标准指定网站发送GET请求、post请求类、ttpUrlConnection继承自URLConnection,可用于向指定网站发送GET请求、post请求，httpUrlConnection在使用上相对简单，并且易于扩展，推荐使用。

二、如何使用HttpUrlCnnection

   1.创建URL对象。

   2.通过URL对象调用openConnection()方法获得HttpURLConnection对象。

   3.HttpURLConnection对象设置其它连接属性。

   4.HttpURLConnection对象调用getInputstream()方法下向服务器发送http请求并获取到服务器返回的输入流。

   5读取输入流，转换成String字符串。

三、使用HttpUrlConnection获取Http请求

public class MainActivity extends AppCompatActivity {

 

   private Button getwebBtn;

 

 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        bindID();

 

        getwebBtn.setOnClickListener(new View.OnClickListener() {

    @Override

    public void onClick(View view) {

        new Thread(new Runnable() {

            @Override

            public void run() {

                getWebInfo();

            }

        }).start();

    }

});

 

 

 

    }

 

    private void getWebInfo() {

 

        try {

                //找水源，创建URL

                URL url=new URL("http://mp.blog.csdn.net/postedit/79528472/");

                //开水闸-openConnection

                HttpURLConnection httpURLConnection= (HttpURLConnection) url.openConnection();

                //建水管-InputStream

                InputStream inputStream=httpURLConnection.getInputStream();

                //建蓄水池蓄水-InputStreamReader

                InputStreamReader reader=new InputStreamReader(inputStream,"UTF-8");

                //水桶盛水-BufferedReader

                BufferedReader bufferedReader=new BufferedReader(reader);

 

                StringBuffer stringBuffer= new StringBuffer();

                String temp=null;

 

                while ((temp=bufferedReader.readLine())!=null){

                    stringBuffer.append(temp);

                }

                bufferedReader.close();

                reader.close();

                inputStream.close();

 

                Log.e("MAIN",stringBuffer.toString());

 

 

 

 

            } catch (MalformedURLException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }

 

    }

 

 

    private void bindID() {

        getwebBtn=findViewById(R.id.getweb_btn);

    }

    class MyThread implements Runnable{

 

        @Override

        public void run() {

 

        }

}

 

Xml:

 

<Button

    android:text="点击进入"

    android:id="@+id/getweb_btn"

    android:layout_width="match_parent"

    android:layout_height="50dp" />

 

四、使用HttpURLConnection加载网络图片

加载网络图片，需要用到Bitmap对象。 
加载网络图片有时也需耗时较长时间，所以也应该异步加载。 

ImgActivity代码如下：

package lenovo.wangmengyuan.http;

 

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.ProgressBar;

 

public class ImgActivity extends AppCompatActivity {

    private Button loadbt;

    private ImageView loadimg;

    private ProgressBar progressBar;

 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_img);

        bindID();

        loadbt.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View view) {

         //       ImgloadTask task=new ImgloadTask(loadimg);

             //   task.execute("http://img5.imgtn.bdimg.com/it/u=717372819,1556613902&fm=27&gp=0.jpg");

                loadbt.setEnabled(false);

                 

 

            }

        });

    }

 

    private void bindID() {

        loadbt=findViewById(R.id.loadpig_bt);

        loadimg=findViewById(R.id.loadpig_img);

    }

}

 

XML：

 

<Button

    android:text="点击下载"

    android:id="@+id/loadpig_bt"

    android:layout_width="match_parent"

    android:layout_height="50dp" />

<ImageView

 

    android:scaleType="fitCenter"

    android:id="@+id/loadpig_img"

    android:layout_width="match_parent"

    android:layout_height="match_parent" />

 

ImgLoadTask：

 

package lenovo.wangmengyuan.http;

 

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.os.AsyncTask;

import android.widget.ImageView;

 

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

 

/**

 * Created by Administrator on 2018/3/13.

 */

 

public class ImgloadTask extends AsyncTask<String,Integer,Bitmap> {

 

private ImageView imageView;

    //为什么要加一个构造方法-因为我们有传值的需求

    public  ImgloadTask(ImageView iv){

        this.imageView=iv;

    }

    @Override

    protected Bitmap doInBackground(String... strings) {

 

        Bitmap bm=null;

        try {

          URL  url = new URL(strings[0]);

            HttpURLConnection connection= (HttpURLConnection) url.openConnection();

            InputStream inputStream=connection.getInputStream();

            bm= BitmapFactory.decodeStream(inputStream);

        } catch (MalformedURLException e) {

            e.printStackTrace();

        }

        catch (IOException e) {

            e.printStackTrace();

 

        }

 

 

        //加载网络图片，最后获取到一个Bitmap对象，返回Bitmap对象

        return bm;

    }

 

    @Override

    protected void onPostExecute(Bitmap s) {

        super.onPostExecute(s);

        imageView.setImageBitmap(s);

    }

}

 

五、使用HttpURLConnection下载网络资源

ImgActivity.java代码：

package lenovo.wangmengyuan.http;

 

import android.Manifest;

import android.support.annotation.NonNull;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.ProgressBar;

 

import com.master.permissionhelper.PermissionHelper;

 

import java.security.Permission;

 

public class ImgActivity extends AppCompatActivity {

    private Button loadbt;

    private ImageView loadimg;

    private ProgressBar progressBar;

    private String picUrl="http://http://pic3.nipic.com/20090623/2512829_165609054_2.jpg";

    private PermissionHelper permissionHelper;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_img);

        bindID();

      loadbt.setOnClickListener(new View.OnClickListener() {

          @Override

          public void onClick(View view) {

 

permissionHelper=new PermissionHelper(ImgActivity.this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},100);

       permissionHelper.request(new PermissionHelper.PermissionCallback() {

           @Override

           public void onPermissionGranted() {

               DownLoad2 task=new DownLoad2(ImgActivity.this,loadimg);

               task.execute(picUrl,"ghh.jpg");

 

           }

 

           @Override

           public void onIndividualPermissionGranted(String[] grantedPermission) {

 

           }

 

           @Override

           public void onPermissionDenied() {

 

           }

 

           @Override

           public void onPermissionDeniedBySystem() {

 

           }

       });

 

// new DownLoad2(ImgActivity.this,loadimg).execute(picUrl,"gff.jpg");

 

 

          }

      });

 

 

         //       ImgloadTask task=new ImgloadTask(loadimg);

             //   task.execute("http://img5.imgtn.bdimg.com/it/u=717372819,1556613902&fm=27&gp=0.jpg");

                //loadbt.setEnabled(false);

               // DownLoadTask dTask = new DownLoadTask(ImgActivity.this,loadbt,progressBar);

               // dTask.execute("http://img1.bitautoimg.com/bitauto/2012/09/17/a50cdcf8-1a2a-418b-b7be-d81f36ab12ee.jpg","fra.jpg");

 

 

 

            }

 

    private void bindID() {

        loadbt=findViewById(R.id.loadpig_bt);

        loadimg=findViewById(R.id.loadpig_img);

    }

 

    @Override

    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (permissionHelper!=null){

            permissionHelper.onRequestPermissionsResult(requestCode, permissions, grantResults);

        }

    }

}

 

DownLoad2代码如下

 

public class DownLoad2 extends AsyncTask<String,Integer,Integer> {

 

 

    private String dirPath;//下载目录的途径

    private String filePath;//文件储存位置，列入

    private ImageView loading;

    private Context context;

    public   DownLoad2(Context context,ImageView loading){

    this.context=context;

     this.loading=loading;

}

 

    InputStream inputStream=null;

    OutputStream o =null;

    @Override

    protected Integer doInBackground(String... strings) {

        String fileName=strings[1];//存储图片的名字

        //判断目录是否存在，不存在，创建目录

        dirPath= Environment.getExternalStorageDirectory() + "/"+"http_download/";

        File dir=new File(dirPath);//创建文件对象

        if (dir.exists()){

            dir.mkdir();

        }

//判断文件是否存在，不存在创建

        filePath=dirPath+fileName;

        File file=new File(filePath);

        if (file.exists()){

            return -1;

 

        }

        else {

            try {

                file.createNewFile();//不存在创建新的

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        InputStream inputStream=null;

        FileOutputStream outputStream=null;

 

 

        URL url= null;

        try {

            url = new URL(strings[0]);

        } catch (MalformedURLException e) {

            e.printStackTrace();

        }

        try {

            HttpURLConnection connection= (HttpURLConnection) url.openConnection();

            if (connection.getResponseCode()==200){

                //判断返回码是否正常，若

                inputStream=connection.getInputStream();

            }

            else {

                return -2;

            }

            outputStream=new FileOutputStream(file);

            int length=0;

            byte[] buffer=new byte[4*1024];

            while ((length=inputStream.read(buffer))!=-1){

                outputStream.write(buffer,0,length);

 

 

            }

            outputStream.close();

            inputStream.close();

 

 

 

        } catch (IOException e) {

            e.printStackTrace();

        }

 

        return 1;

    }

 

    @Override

    protected void onPostExecute(Integer integer) {

        super.onPostExecute(integer);

        switch (integer){

            case 1:

                //正常下载完成

                Toast.makeText(context,"下载完成",Toast.LENGTH_SHORT).show();

                Bitmap bm= BitmapFactory.decodeFile(filePath);

                loading.setImageBitmap(bm);

                break;

            case -1:

                //文件已存在

                Toast.makeText(context,"文件已存在",Toast.LENGTH_SHORT).show();

                break;

            case -2:

                //网络异常

                Toast.makeText(context,"网络异常",Toast.LENGTH_SHORT).show();

                break;

        }

    }

 

外加文件读取权限以及网络请求权限：

<uses-permission android:name="android.permission.INTERNET"/>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>