1）只显示网络图片

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"tools:context="dujun.king.urlgetimage.MainActivity" ><ImageViewandroid:id="@+id/imageView1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_centerHorizontal="true"android:layout_marginBottom="196dp"android:src="@drawable/ic_launcher" /></RelativeLayout>

b)MainActivity.java

package dujun.king.urlgetimage;import java.io.InputStream;
import java.net.URL;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.widget.ImageView;public class MainActivity extends Activity {Bitmap bitmap;ImageView imageview;Handler handler=new Handler(){@Overridepublic void handleMessage(Message msg) {if (msg.what==0x9527) {//显示从网上下载的图片imageview.setImageBitmap(bitmap);}}          };@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);imageview=(ImageView)findViewById(R.id.imageView1);     //创建并启动一个新线程用于从网络上下载图片new Thread(){@Overridepublic void run() {try {//创建一个url对象URL url=new URL("http://www.baidu.com/img/bdlogo.png");//打开URL对应的资源输入流InputStream is= url.openStream();//从InputStream流中解析出图片bitmap = BitmapFactory.decodeStream(is);//  imageview.setImageBitmap(bitmap); //发送消息，通知UI组件显示图片handler.sendEmptyMessage(0x9527);//关闭输入流is.close();} catch (Exception e) {e.printStackTrace();}}          }.start();}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {// Handle action bar item clicks here. The action bar will// automatically handle clicks on the Home/Up Button, so long// as you specify a parent activity in AndroidManifest.xml.int id = item.getItemId();if (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}
}

c）AndroidMainifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="dujun.king.urlgetimage"android:versionCode="1"android:versionName="1.0" ><uses-sdkandroid:minSdkVersion="15"android:targetSdkVersion="15" /><!-- 访问Internet权限 --><uses-permission android:name="android.permission.INTERNET"/><applicationandroid:allowBackup="true"android:icon="@drawable/ic_launcher"android:Label="@string/app_name"android:theme="@style/AppTheme" ><activityandroid:name=".MainActivity"android:label="@string/app_name" ><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity></application></manifest>

2）如果我们要显示并下载网络图片，只需要将MainActivity.java文件修改如下：

package dujun.king.urlgetimage;import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;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.widget.ImageView;public class MainActivity extends Activity {Bitmap bitmap;ImageView imageview;Handler handler=new Handler(){@Overridepublic void handleMessage(Message msg) {if (msg.what==0x9527) {//显示从网上下载的图片imageview.setImageBitmap(bitmap);}}          };@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);imageview=(ImageView)findViewById(R.id.imageView1);     //创建并启动一个新线程用于从网络上下载图片//这里必须新起一个线程，Android后面的版本中，不允许在主线程中联网new Thread(){@Overridepublic void run() {try {//创建一个url对象URL url=new URL("http://www.baidu.com/img/bdlogo.png");//打开URL对应的资源输入流InputStream is= url.openStream();//从InputStream流中解析出图片bitmap = BitmapFactory.decodeStream(is);//  imageview.setImageBitmap(bitmap); //发送消息，通知UI组件显示图片handler.sendEmptyMessage(0x9527);//关闭输入流is.close();//------------------------------//下载网络图片//再次打开资源流is = url.openStream();//打开手机对应的输出流//存放在手机中，并命名为baidulogo.pngOutputStream os = openFileOutput("baidulogo.png", MODE_WORLD_READABLE);byte[] buff = new byte[1024];int len = 0;//因为网络下载一般不可能一次下载完毕，我们将每次下载好的有效数据写入while ((len = is.read(buff)) > 0){os.write(buff,0,len);}//关闭流is.close();os.close();} catch (Exception e) {e.printStackTrace();}}          }.start();}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {// Handle action bar item clicks here. The action bar will// automatically handle clicks on the Home/Up button, so long// as you specify a parent activity in AndroidManifest.xml.int id = item.getItemId();if (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}
}