常规做法：

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

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context=".MainActivity" >

android:id="@+id/iv_icon"

android:layout_width="fill_parent"

android:layout_height="0dip"

android:layout_weight="1" />

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

android:id="@+id/et_url"

android:layout_width="0dip"

android:text="http://imgstatic.baidu.com/img/image/d833c895d143ad4bf450b6dd80025aafa40f06b4_%E5%89%AF%E6%9C%AC.jpg"

android:layout_height="wrap_content"

android:singleLine="true"

android:layout_weight="1" />

android:id="@+id/btn_submit"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Go"

android:textSize="20sp" />

package com.itheima28.netphoto;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import javax.net.ssl.HttpsURLConnection;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.app.Activity;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.util.Log;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.EditText;

import android.widget.ImageView;

import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

private static final String TAG = "MainActivity";

protected static final int ERROR = 1;

private EditText etUrl;

private ImageView ivIcon;

private final int SUCCESS = 0;

private Handler handler = new Handler() {

/**

* 接收消息

*/

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

Log.i(TAG, "what = " + msg.what);

if(msg.what == SUCCESS) {// 当前是访问网络, 去显示图片

ivIcon.setImageBitmap((Bitmap) msg.obj);// 设置imageView显示的图片

} else if(msg.what == ERROR) {

Toast.makeText(MainActivity.this, "抓去失败", 0).show();

}

}

};

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

ivIcon = (ImageView) findViewById(R.id.iv_icon);

etUrl = (EditText) findViewById(R.id.et_url);

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

}

@Override

public void onClick(View v) {

final String url = etUrl.getText().toString();

new Thread(new Runnable() {

@Override

public void run() {

Bitmap bitmap = getImageFromNet(url);

//ivIcon.setImageBitmap(bitmap);// 设置imageView显示的图片

if(bitmap != null) {

Message msg = new Message();

msg.what = SUCCESS;

msg.obj = bitmap;

handler.sendMessage(msg);

} else {

Message msg = new Message();

msg.what = ERROR;

handler.sendMessage(msg);

}

}}).start();

}

/**

* 根据url连接取网络抓去图片返回

* @param url

* @return url对应的图片

*/

private Bitmap getImageFromNet(String url) {

HttpURLConnection conn = null;

try {

URL mURL = new URL(url);// 创建一个url对象

// 得到http的连接对象

conn = (HttpURLConnection) mURL.openConnection();

conn.setRequestMethod("GET");// 设置请求方法为Get

conn.setConnectTimeout(10000);// 设置连接服务器的超时时间, 如果超过10秒钟, 没有连接成功, 会抛异常

conn.setReadTimeout(5000);// 设置读取数据时超时时间, 如果超过5秒, 抛异常

conn.connect();// 开始链接

int responseCode = conn.getResponseCode(); // 得到服务器的响应码

if(responseCode == 200) {

// 访问成功

InputStream is = conn.getInputStream();// 获得服务器返回的流数据

Bitmap bitmap = BitmapFactory.decodeStream(is); // 根据 流数据 创建一个bitmap位图对象

return bitmap;

} else {

Log.i(TAG, "访问失败: responseCode = " + responseCode);

}

} catch (Exception e) {

e.printStackTrace();

} finally {

if(conn != null) {

conn.disconnect();// 断开连接

}

}

return null;

}

}

使用com.loopj.android.image组件

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

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context=".MainActivity" >

android:id="@+id/iv_icon"

android:layout_width="fill_parent"

android:layout_height="0dip"

android:layout_weight="1" />

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

android:id="@+id/et_url"

android:layout_width="0dip"

android:text="http://imgstatic.baidu.com/img/image/d833c895d143ad4bf450b6dd80025aafa40f06b4_%E5%89%AF%E6%9C%AC.jpg"

android:layout_height="wrap_content"

android:singleLine="true"

android:layout_weight="1" />

android:id="@+id/btn_submit"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Go"

android:textSize="20sp" />

package com.itheima28.netphoto;

import com.loopj.android.image.SmartImageView;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.EditText;

public class MainActivity2 extends Activity implements OnClickListener {

private EditText etUrl;

private SmartImageView mImageView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main2);

etUrl = (EditText) findViewById(R.id.et_url);

mImageView = (SmartImageView) findViewById(R.id.iv_icon);

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

}

@Override

public void onClick(View v) {

// 1. 取出url, 抓取图片

String url = etUrl.getText().toString();

mImageView.setImageUrl(url);

}

}

需要访问网络的权限