Android中显示网络图片

在Android中，显示网络图片还是比较简单的。当我们开始启动一个任务加载一个View对应的图片时，应该通过setTag()把该View的tag设置为图片的URL.当实际取得该图片时，应该检查其对应的URL是否和View的TAG一致，只有一致时才把该图片实际应用于该View.

实例1

InternetImageDemoActivity.java文件

package com.lenovo.robin.test;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ImageView;
public class InternetImageDemoActivity extends Activity {
 Bitmap bmImg;
 ImageView imView;
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.internet_image_demo);
  imView = (ImageView) findViewById(R.id.imageView1);
  String imageUrl = "http://img6.ph.126.net/hBiG96B8egigBULxUWcOpA==/109212290980771276.jpg";
  final ImageView imageView = imView;
  imageView.setTag(imageUrl);
  ImageLoadedCallback callback = new ImageLoadedCallback() {
   @Override
   public void loaded(Bitmap bitMap, String url) {
    // TODO Auto-generated method stub
    if (url.equals(imageView.getTag())) {
     imageView.setImageBitmap(bitMap);
    }
   }
  };
  new DownloadImageTask(callback).execute(imageUrl);
 }
}

class DownloadImageTask extends AsyncTask<String, Integer, Bitmap> {
 ImageLoadedCallback callback = null;
 String url = null;
 DownloadImageTask(ImageLoadedCallback callback) {
  this.callback = callback;
 }
 protected Bitmap doInBackground(String... urls) {
  URL myFileUrl = null;
  Bitmap bitmap = null;
  url = urls[0];
  try {
   myFileUrl = new URL(url);
  } catch (MalformedURLException e) {
   e.printStackTrace();
  }
  HttpURLConnection conn=null;
  InputStream is=null;
  try {
   conn = (HttpURLConnection) myFileUrl
     .openConnection();
   conn.setDoInput(true);
   conn.connect();
   is = conn.getInputStream();
   bitmap = BitmapFactory.decodeStream(is);
   is.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
  finally
  {
   if(conn!=null)
   {
    try {
     conn.connect();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
    conn=null;
   }
   if(is!=null)
   {
    try {
     is.close();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
    is=null;
   }
  }
  return bitmap;
 }
 protected void onPostExecute(Bitmap bitMap) {
  callback.loaded(bitMap, url);
 }
}

interface ImageLoadedCallback {
 public void loaded(Bitmap bitMap, String url);
}

关于AsyncTask请参照《AsyncTask简介》

布局文件internet_image_demo.xml

<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" >
    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="34dp"
  />
</RelativeLayout>

另外在AndroidManifest.xml中需要添加以