Android从网络中获得一张图片并显示在屏幕上的实例详解

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
   package="cn.capinftotech.image" 
   android:versionCode="1" 
   android:versionName="1.0"> 
  <application android:icon="@drawable/icon" android:label="@string/app_name"> 
    <activity android: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> 
  <uses-sdk android:minSdkVersion="8" /> 
  <uses-permission android:name="android.permission.INTERNET" /> 
 
</manifest>  

package cn.capinftotech.image; 
 
import java.io.IOException; 
 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ImageView; 
import android.widget.Toast; 
 
import com.capinfotech.service.ImageService; 
 
public class MainActivity extends Activity { 
  private static final String TAG = "MainActivity"; 
   
  private EditText urlPath = null; 
  private Button button = null; 
  private ImageView imageView = null; 
   
  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
     
    urlPath = (EditText)findViewById(R.id.urlpath); 
    button = (Button)findViewById(R.id.button); 
    imageView = (ImageView)findViewById(R.id.imageView); 
     
    button.setOnClickListener(new View.OnClickListener() { 
       
      @Override 
      public void onClick(View v) { 
        String urlPathContent = urlPath.getText().toString(); 
        try { 
          byte[] data = ImageService.getImage(urlPathContent); 
          Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length); //生成位图 
          imageView.setImageBitmap(bitmap);  //显示图片 
        } catch (IOException e) { 
          Toast.makeText(MainActivity.this, R.string.error, Toast.LENGTH_LONG).show(); //通知用户连接超时信息 
          Log.i(TAG, e.toString()); 
        } 
         
      } 
    }); 
  } 
} 

package com.capinfotech.service; 
 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 
 
import com.capinfotech.utils.StreamTool; 
 
public class ImageService { 
   
  public static byte[] getImage(String path) throws IOException { 
    URL url = new URL(path); 
    HttpURLConnection conn = (HttpURLConnection)url.openConnection(); 
    conn.setRequestMethod("GET");  //设置请求方法为GET 
    conn.setReadTimeout(5*1000);  //设置请求过时时间为5秒 
    InputStream inputStream = conn.getInputStream();  //通过输入流获得图片数据 
    byte[] data = StreamTool.readInputStream(inputStream);   //获得图片的二进制数据 
    return data; 
     
  } 
} 

package com.capinfotech.utils; 
 
import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
 
public class StreamTool { 
 
  /* 
   * 从数据流中获得数据 
   */ 
  public static byte[] readInputStream(InputStream inputStream) throws IOException { 
    byte[] buffer = new byte[1024]; 
    int len = 0; 
    ByteArrayOutputStream bos = new ByteArrayOutputStream(); 
    while((len = inputStream.read(buffer)) != -1) { 
      bos.write(buffer, 0, len); 
    } 
    bos.close(); 
    return bos.toByteArray(); 
     
  } 
} 

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
  <string name="hello">Hello World, MainActivity!</string> 
  <string name="app_name">图片浏览器</string> 
  <string name="urlpath">网络图片地址</string> 
  <string name="button">显示</string> 
  <string name="error">网络连接超时</string> 
</resources> 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" 
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent" 
  > 
<TextView  
  android:layout_width="fill_parent"  
  android:layout_height="wrap_content"  
  android:text="@string/urlpath" 
  /> 
<EditText  
  android:id="@+id/urlpath" 
  android:layout_width="fill_parent"  
  android:layout_height="wrap_content"  
  android:text="http://www.eoeandroid.com/data/attachment/forum/201107/18/142935bbi8d3zpf3d0dd7z.jpg" 
  /> 
<Button 
  android:id="@+id/button" 
  android:layout_width="wrap_content"  
  android:layout_height="wrap_content"  
  android:text="@string/button" 
  /> 
<ImageView 
  android:id="@+id/imageView" 
  android:layout_width="wrap_content"  
  android:layout_height="wrap_content"  
/> 
</LinearLayout>