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android中的HttpUrlConnection的使用之二
httpUrlConnection主要用于网络传输当中，前面已经提及到了使用HttpUrlConnection来加载一个网站，这里我记录一下：用它在网络上下载一张图片并且加载到imageview当中。我们需要注意的是：当前很多网站上的图片传输的模式主要分两种：1.一是加密传输，使用HttpsUrlConnection进行链接；2.而是非加密传输，使用HttpUrlConnection来传输。代码如下（非加密传输）：
xml代码
1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 android:layout_width="match_parent" 4 android:layout_height="match_parent" 5 tools:context="com.example.android_http2.MainActivity" > 6 <ImageView 7 android:layout_gravity="center" 8 android:id="@+id/imageview" 9 android:layout_width="wrap_content"10 android:layout_height="wrap_content"11 />12 13 </LinearLayout>
Java代码
首先创建了一个MainActivity类，来对ui进行更新的操作。
1 package com.example.android_http2; 2 3 import android.app.Activity; 4 import android.os.Bundle; 5 import android.os.Handler; 6 import android.widget.ImageView; 7 8 public class MainActivity extends Activity { 9 private ImageView imageview = null;10 private Handler handler = new Handler();11 @Override12 protected void onCreate(Bundle savedInstanceState) {13 super.onCreate(savedInstanceState);14 setContentView(R.layout.activity_main);15 imageview = (ImageView) findViewById(R.id.imageview);16 new HttpThread("http://img.mp.itc.cn/upload/20160416/5cbd639a2bbf41ffa68147df01254444_th.jpg", imageview, handler).start();17 }18 19 }
其次，创建一个线程类，来进行异步下载的功能。将网络上的代码先下载到本地上去，然后在用handler来通知主线程更新ui。
1 package com.example.android_http2; 2 3 import java.io.File; 4 import java.io.FileNotFoundException; 5 import java.io.FileOutputStream; 6 import java.io.IOException; 7 import java.io.InputStream; 8 import java.net.HttpURLConnection; 9 import java.net.MalformedURLException; 10 import java.net.URL; 11 12 import javax.net.ssl.HttpsURLConnection; 13 14 import android.graphics.Bitmap; 15 import android.graphics.BitmapFactory; 16 import android.os.Environment; 17 import android.os.Handler; 18 import android.util.Log; 19 import android.widget.ImageView; 20 21 public class HttpThread extends Thread{ 22 private String url = null; 23 private ImageView imageview = null; 24 private Handler handler = null; 25 public HttpThread (String url, ImageView imageview, Handler handler) 26 { 27 this.handler = handler; 28 this.imageview = imageview; 29 this.url = url; 30 } 31 public void run() { 32 HttpURLConnection httpurlconnection = null; 33 try { 34 URL url = new URL(this.url); 35 httpurlconnection = (HttpURLConnection) url.openConnection(); 36 } catch (MalformedURLException e) { 37 // TODO Auto-generated catch block 38 e.printStackTrace(); 39 } catch (IOException e) { 40 // TODO Auto-generated catch block 41 e.printStackTrace(); 42 } 43 InputStream in = null; 44 try { 45 httpurlconnection.setReadTimeout(5000); 46 //允许获得输入流 47 httpurlconnection.setDoInput(true); 48 in = httpurlconnection.getInputStream(); 49 } catch (IOException e1) { 50 // TODO Auto-generated catch block 51 e1.printStackTrace(); 52 } 53 FileOutputStream out = null; 54 File downfile = null; 55 //判断当前的内存卡是否可以用 56 Log.i("main", "我进来没1?"); 57 File file = null; 58 if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) 59 { 60 Log.i("main", "我进来没?"); 61 file = new File(Environment.getExternalStorageDirectory().toString() + File.separator + "imageviewdown" + File.separator + "image.jpg"); 62 if(!file.getParentFile().exists()) 63 { 64 file.getParentFile().mkdirs(); 65 66 } 67 else if(!file.exists()) 68 { 69 Log.i("main", "我进来没? 62"); 70 try { 71 file.createNewFile(); 72 } catch (IOException e) { 73 // TODO Auto-generated catch block 74 e.printStackTrace(); 75 } 76 } 77 try { 78 out = new FileOutputStream(file); 79 } catch (FileNotFoundException e) { 80 Log.i("main", "异常没?"); 81 e.printStackTrace(); 82 } 83 } 84 byte buff[] = new byte[2 * 1024]; 85 int len = 0; 86 try { 87 while((len = in.read(buff)) != -1) 88 { 89 out.write(buff, 0,len); 90 } 91 } catch (IOException e) { 92 // TODO Auto-generated catch block 93 e.printStackTrace(); 94 } 95 //将下载在本地的图片加载在一个bitmap当中来 96 final Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath()); 97 Log.i("main", file.getAbsolutePath()); 98 //通知主线程来更新ui 99 handler.post(new Runnable() {100 public void run() {101 imageview.setImageBitmap(bitmap);102 }103 });104 }105 106 }
android中的HttpUrlConnection的使用之二
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