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接之前一篇博客中介绍到服务器返回JSON数据给安卓客户端，本篇在此基础上增加了图片的下载和ListView显示的功能。首先添加一个ListView的简单布局如下，ListView中显示的内容为图片、名称和价格。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/vview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/listviewbackground"
android:paddingBottom="5dp"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:paddingTop="5dp" >
<ImageView
android:id="@+id/image"
android:layout_width="80dp"
android:layout_height="65dp"
android:src="@drawable/image_loading" />
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_toRightOf="@id/image"
android:textColor="#000000"
android:textSize="13dp"
android:textStyle="italic" />
<TextView
android:id="@+id/time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_below="@id/title"
android:layout_marginLeft="5dp"
android:layout_marginTop="5dp"
android:layout_toRightOf="@id/image"
android:textColor="#000000"
android:textSize="11dp" />
</RelativeLayout>
接下来需要为ListView自定义一个适配器，自定义的这个适配器继承于ArrayAdapter<PictureBean>，在自定义适配器的构造方法中直接调用父类的构造方法将PictureBean对象部署到适配器中，然后重写其getView方法，为ListView中的控件添加显示内容。这部分的代码如下：
package com.example.restaurant;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.domain.PictureBean;
public class MyImageAndTextListAdapter extends ArrayAdapter<PictureBean> {
public MyImageAndTextListAdapter(Context context, List<PictureBean> newsList) {
super(context, 0, newsList);
}
private Map<Integer, View> viewMap = new HashMap<Integer, View>();
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View rowView = this.viewMap.get(position);
if (rowView == null) {
LayoutInflater inflater = ((Activity) this.getContext())
.getLayoutInflater();
rowView = inflater.inflate(R.layout.item, null);
PictureBean picture = this.getItem(position);
TextView textView = (TextView) rowView.findViewById(R.id.title);
textView.setText(picture.getName());
TextView textView2 = (TextView) rowView.findViewById(R.id.time);
textView2.setText("价格：" + picture.getPrice());
ImageView imageView = (ImageView) rowView.findViewById(R.id.image);
String str = picture.getName() + "$" + picture.getPrice() + ".jpg";
Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/restaurant/"
+ str);
imageView.setImageBitmap(bitmap);
viewMap.put(position, rowView);
}
return rowView;
}
}
添加完布局和适配器之后，接下来进行数据的读取和显示工作。在MainActivity的onCreate()方法中首先判断数据库中是否有数据，若数据库为空则从服务器端读取数据，若不为空则直接从数据库中读取数据。从服务器中获取数据的代码如下：
/**
* 从服务器获取图片信息并将图片保存在SDCard上
*/
private void updateFromServer() {
showProgressDialog();
getInfoThread = new Thread(new Runnable() {
@Override
public void run() {
try {
// 获得从服务器返回的图片信息和路径 JSON
Pictures = UptadePictureService.getJSONPictures();
} catch (Exception e) {
// Toast.makeText(MainActivity.this, "连接服务器失败！",
// Toast.LENGTH_SHORT).show();
} finally {
downOK = true;
}
}
});
getInfoThread.start();
/**
* 下载图片线程
*/
getPictureThread = new Thread(new Runnable() {
@Override
public void run() {
try {
// 等待获取图片信息线程执行完毕
while (getInfoThread.getState() != Thread.State.TERMINATED) {
}
for (PictureBean picture : Pictures) {
/**
* 对传递进来的path进行处理
* 例如：E:\webTest\Restaurant\WebContent\Pictures
* \川菜\四喜丸子$22.jpg
* 将其转换成：Restaurant/Pictures/川菜/四喜丸子$22.jpg
*/
String str = picture.getName() + "$"
+ picture.getPrice() + ".jpg";
Bitmap bitmap = BitmapFactory
.decodeFile("/sdcard/restaurant/" + str);
if (bitmap == null) {
String url = picture.getPath();
String[] strList = url.split("\\\\");
url = strList[2] + "/" + strList[4] + "/"
+ strList[5] + "/" + strList[6];
// 下载图片并保存在SD卡中
down_file("http://192.168.1.103:8080/" + url,
"/sdcard/restaurant/");
}
}
Message msg = new Message();
msgHandle.sendMessage(msg);
} catch (Exception e) {
// Toast.makeText(MainActivity.this, "连接服务器失败！",
// Toast.LENGTH_SHORT).show();
} finally {
}
}
});
getPictureThread.start();
}
public void down_file(String url, String path) throws Exception {
String filename = url.substring(url.lastIndexOf("/") + 1);
/**
* 处理中文路径 ：由于URLEncoder.encode会对‘/‘和‘:‘进行转码，通过下面的代码可以避免这种错误
*/
String[] strList = url.split("\\/");
url = "";
for (String mstr : strList) {
if (mstr.contains(":")) {
url = url + mstr + "/";
} else {
url = url + URLEncoder.encode(mstr, "utf-8") + ‘/‘;
}
}
url = url.substring(0, url.length() - 1);
Log.d("MainActivity", url);
URL myURL = new URL(url);
HttpURLConnection conn = (HttpURLConnection) myURL.openConnection();
conn.setConnectTimeout(5000);
conn.setRequestMethod("GET");
if (conn.getResponseCode() == 200) {
InputStream inputStream = conn.getInputStream();
File file = new File(path);
if (!file.exists()) {
file.mkdir();
}
FileOutputStream out = new FileOutputStream(path + filename);
// 把数据存入路径+文件名
byte buf[] = new byte[1024];
do {
// 循环读取
int numread = inputStream.read(buf);
if (numread == -1) {
break;
}
out.write(buf, 0, numread);
} while (true);
inputStream.close();
}
}
接下来添加一个更新菜单按钮，该按钮可以从服务器获取最新的菜单信息。把应用部署到安卓模拟器上，基本的效果如下图所示：
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原文地址：http://www.cnblogs.com/xiaoxiongbb/p/4665620.html
