安卓获取服务器返回的图片资源路径并下载图片

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。这里要特别注意的是中文路径的URI编码,为了保证能够访问服务器中的中文路径,需要在server.xml中配置编码格式为“utf-8”格式,<Connector connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443" URIEncoding="utf-8"/>,同时,在客户端中需要对中文进行URI编码,格式同样保证为"utf-8"。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,改变服务器中的图片名称,从客户端可以更新到最新的图片数据。

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