Android学习笔记_12_网络通信之从web获取资源数据到Android

    从web获取图片信息，并显示到android的imageView控件。

　　一、添加网络访问权限。

<uses-permission android:name="android.permission.INTERNET"/>

　　二、界面布局及activity的实现：

<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=".MainActivity" >

    <Button
        android:id="@+id/btnImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="34dp"
        android:layout_marginTop="15dp"
        android:text="查看图片" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/btnImage"
        android:layout_below="@+id/btnImage"
        android:layout_marginTop="20dp"
         />

</RelativeLayout>

package com.example.image;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity {
    private Button button = null;
    private ImageView imageView;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button) this.findViewById(R.id.btnImage);
        imageView = (ImageView) this.findViewById(R.id.imageView);
        final String path="http://192.168.8.103:8080/Simple/0001.jpg";
        button.setOnClickListener(new OnClickListener() {        
            @Override
            public void onClick(View view) {
                try {
                    byte[] data = getImage(path);
                    Bitmap bm=BitmapFactory.decodeByteArray(data, 0, data.length);
                    imageView.setImageBitmap(bm);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });        
    }
    /**
     * 获取图片流
     * @param path
     * @return
     * @throws Exception
     */
    public static byte[] getImage(String path) throws Exception{
       //创建URL对象，获取HttpURLConnection
        HttpURLConnection conn = (HttpURLConnection) new URL(path).openConnection();
        conn.setConnectTimeout(5000);
        conn.setRequestMethod("GET");
        if (conn.getResponseCode()==200) {
            //处理从web返回的资源数据
            return read(conn.getInputStream());
        }        
        return null;
    }
    /**
     * 将流转化成字节数组
     * @param in
     * @return
     * @throws Exception
     */
    public static byte[] read(InputStream in) throws Exception{
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];
        int len=0;
        while((len=in.read(buf))!=-1){
            outputStream.write(buf,0,len);
        }
        outputStream.close();
        return outputStream.toByteArray();    
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}