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1 package com.example.day10_01getpicture; 2 3 import java.io.InputStream; 4 import java.net.HttpURLConnection; 5 import java.net.URL; 6 7 import android.app.Activity; 8 import android.graphics.Bitmap; 9 import android.graphics.BitmapFactory; 10 import android.os.Bundle; 11 import android.os.Handler; 12 import android.os.Message; 13 import android.view.View; 14 import android.widget.ImageView; 15 import android.widget.Toast; 16 17 public class MainActivity extends Activity { 18 19 @Override 20 protected void onCreate(Bundle savedInstanceState) { 21 super.onCreate(savedInstanceState); 22 setContentView(R.layout.activity_main); 23 } 24 25 final static int MSG_DOWNLOAD_OK =1; 26 final static int MSG_DOWNLOAD_ERROR =2; 27 28 /* Handler主要用于异步消息的处理:当发出一个消息之后,首先进入一个消息队列,发送消息的函数即刻返回, 29 *而另外一个部分逐个的在消息队列中将消息取出,然后对消息进行出来,就是发送消息和接收消息不是同步的处理。 30 *这种机制通常用来处理相对耗时比较长的操作*/ 31 Handler handler = new Handler(){ 32 @Override 33 public void handleMessage(Message msg) { 34 super.handleMessage(msg); 35 //针对message进行处理 36 switch (msg.what) { 37 case MSG_DOWNLOAD_OK: 38 ImageView iv= (ImageView) findViewById(R.id.iv_pic); 39 iv.setImageBitmap((Bitmap)msg.obj); 40 break; 41 case MSG_DOWNLOAD_ERROR: 42 Toast.makeText(MainActivity.this, "下载失败", 1).show(); 43 break; 44 default: 45 break; 46 } 47 } 48 }; 49 50 51 public void getpicture(View v){ 52 Thread tread = new Thread(){ 53 public void run() { 54 //启动tomcat服务器 55 String path = "http://192.168.3.39/zy.jpg"; 56 try { 57 URL url = new URL(path); 58 HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 59 conn.setReadTimeout(5000); 60 conn.setRequestMethod("GET"); 61 conn.setConnectTimeout(5000); 62 // pending; 63 conn.connect(); 64 65 if (conn.getResponseCode()==200) { 66 InputStream is = conn.getInputStream(); 67 Bitmap bm = new BitmapFactory().decodeStream(is); 68 69 /*子线程内无法操作UI,原因? 70 ImageView iv= (ImageView) findViewById(R.id.iv_pic); 71 iv.setImageBitmap(bm); 72 让主线程去更新ui--》 通知主线程去做事情,顺便把数据bm给到主线程 73 */ 74 // Message msg = new Message();//ok 75 Message msg = handler.obtainMessage(); 76 msg.what = MSG_DOWNLOAD_OK; 77 msg.obj = bm; 78 handler.sendMessage(msg); 79 } 80 else { 81 // Message msg = new Message();//!ok 82 Message msg = handler.obtainMessage(); 83 msg.what =MSG_DOWNLOAD_ERROR; 84 handler.sendMessage(msg); 85 //Toast.makeText(this, "下载失败", 1).show(); 86 } 87 }catch (Exception e) { 88 e.printStackTrace(); 89 } 90 }; 91 }; 92 tread.start(); 93 } 94 }
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="${relativePackage}.${activityClass}" 6 android:orientation="vertical" > 7 8 <TextView 9 android:layout_width="wrap_content" 10 android:layout_height="wrap_content" 11 android:text="hello_world" /> 12 <Button 13 android:layout_width="wrap_content" 14 android:layout_height="wrap_content" 15 android:text="获取图片" 16 android:onClick="getpicture"/> 17 <ImageView 18 android:id="@+id/iv_pic" 19 android:layout_width="wrap_content" 20 android:layout_height="wrap_content" 21 android:src="@drawable/ic_launcher" 22 ></ImageView> 23 </LinearLayout>
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原文地址:http://www.cnblogs.com/woodrow2015/p/4515053.html