<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

     xmlns:tools="http://schemas.android.com/tools"

     android:layout_width="match_parent"

     android:layout_height="match_parent"

     android:orientation="vertical"

     tools:context="com.zzw.watctImage.MainActivity" >

     <ImageView

         android:id="@+id/image_view"

         android:layout_width="match_parent"

         android:src="@drawable/t01a7b264978bb316f1"

         android:layout_height="wrap_content"

         android:layout_weight="1" />

     <LinearLayout

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:orientation="horizontal" >

         <EditText

             android:id="@+id/url_edit"

             android:layout_width="wrap_content"

             android:layout_height="match_parent"

             android:layout_weight="1"

             android:singleLine="true"

             android:text="http://p1.so.qhimg.com/t017cf2863df563308b.jpg" />

         <Button

             android:id="@+id/get"

             android:layout_width="wrap_content"

             android:layout_height="match_parent"

             android:text="获得图片"

             android:textColor="@android:color/holo_blue_light" />

     </LinearLayout>

 </LinearLayout>

 package com.zzw.watctImage;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.HttpURLConnection;

 import java.net.MalformedURLException;

 import java.net.URL;

 import java.net.URLConnection;

 import android.app.Activity;

 import android.graphics.Bitmap;

 import android.graphics.BitmapFactory;

 import android.os.Bundle;

 import android.os.Handler;

 import android.os.Message;

 import android.view.Menu;

 import android.view.MenuItem;

 import android.view.View;

 import android.view.View.OnClickListener;

 import android.widget.Button;

 import android.widget.EditText;

 import android.widget.ImageView;

 public class MainActivity extends Activity implements OnClickListener {

     ImageView image_view = null;

     EditText image_uri = null;

     Handler handler = new Handler() {

         @Override

         public void handleMessage(Message msg) {

             // TODO Auto-generated method stub

             super.handleMessage(msg);

             if (msg.what == 0) {

                 Bitmap bitmap = (Bitmap) msg.obj;

                 image_view.setImageBitmap(bitmap);

             }

         }

     };

     /**

      * 1.访问网络不能直接放在主方法里面（android.os.NetworkOnMainThreadException）, 应该放在一个线程里面

      * 2.android.view.ViewRootImpl$CalledFromWrongThreadException:

      * 只能在主线程或者UI线程里面修改视图,应该用通信来解决

      */

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.activity_main);

         init();

     }

     // 初始化

     public void init() {

         image_view = (ImageView) findViewById(R.id.image_view);

         image_uri = (EditText) findViewById(R.id.url_edit);

         findViewById(R.id.get).setOnClickListener(this);

     }

     @Override

     public void onClick(View v) {

         final String uri = image_uri.getText().toString();

         new Thread(new Runnable() {

             @Override

             public void run() {

                 // TODO Auto-generated method stub

                 Bitmap bitmap = getBitmap(uri);

                 if (bitmap != null) {

                     Message msg = new Message();

                     msg.what = 0;// 说明你是谁

                     msg.obj = bitmap;

                     handler.sendMessage(msg);

                 }

             }

         }).start();

         ;

     }

     // bitmap------>位图

     public Bitmap getBitmap(String uri) {

         HttpURLConnection conn = null;

         try {

             // 1、获得图片的url

             URL url = new URL(uri);

             // 2、获得网络连接

             conn = (HttpURLConnection) url.openConnection();

             // 3、设置请求的一些常用参数

             conn.setReadTimeout(3000);// 设置连接去读取数据的最长时间

             conn.setConnectTimeout(3000);// 设置超时

             conn.setDoInput(true);// 设置请求可以让服务器写入数据

             // 4、真正的请求图片，然后把从服务器上请求的二进制流保存到inputStream里面

             conn.connect();

             InputStream in = conn.getInputStream();

             Bitmap bitmap = BitmapFactory.decodeStream(in);

             return bitmap;

         } catch (MalformedURLException e) {

             // TODO Auto-generated catch block

             e.printStackTrace();

         } catch (IOException e) {

             // TODO Auto-generated catch block

             e.printStackTrace();

         }

         // 5、关闭网络连接

         finally {

             if (conn != null) {

                 conn.disconnect();

             }

         }

         return null;

     }

 }