Android客户端读取PHP服务器的图片等信息，并用ListView列出来，实现缓存功能。

首先，我就是用很容易理解的方法去实现这个功能。

在服务器端，做一个index.php文件，用来读取MySQL数据库的信息：

index.php：

<?php
$link = mysql_connect("localhost", "root", "123456");
mysql_query("SET NAMES utf8");
mysql_select_db("test", $link); //test为数据库名
$sql = mysql_query("select * from interp_images ", $link); //interp_images 为表名
while ($row = mysql_fetch_assoc($sql))
$output[] = $row;
print (json_encode($output));
mysql_close();
?>

这个PHP文件执行得到的是从数据库表读取出来的所在数据数组。

程序的主代码的一些详解：

ListViewPerformaceActivity .java:

public class ListViewPerformaceActivity extends Activity {
protected static final String TAG = "ListViewPerformaceActivity";
/** Called when the activity is first created. */
private ListView mListview;
ImageLoader mImageLoader = new ImageLoader();
MyAdapter adapter;

private JSONArray jArray;
private String result = null;
private InputStream is = null;
private StringBuilder sb = null;
//private ListView mListView;
private View mView;
private String imageUrl;
private String imageDetailUrl;
private int ct_id;
private String ct_name;
private String ct_detail_name;
private JSONObject json_data = null;

private String[] fileUrl;
private String[] detailUrl;
private int count;

private Bitmap bitmap;
private byte buff[] = new byte[1024 * 250];

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

// TODO http get
try {
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet("http://192.168.18.29/Test/index.php");//IP为自己的服务器的IP因为手机连接局域网的WIFI，所以只用自己的电脑作为服务器也可以测试效果。
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "2013Error in http connection" + e.toString());
}

// convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");

String line = "0";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
e.printStackTrace();
Log.e("log_tag", "Error converting result " + e.toString());
}
// /////////////////////////////////////////////////////////////////////////////
// paring data
try {
jArray = new JSONArray(result);
// JSONObject json_data = null;
count = 0;
detailUrl = new String[jArray.length()];
fileUrl = new String[jArray.length()];
for (int i = 0; i < jArray.length(); i++) { //把读取到数据库表的数据通过for循环添加到数组里
json_data = jArray.getJSONObject(i);
ct_id = json_data.getInt("categoryid");

ct_name = json_data.getString("androidfilename");
imageUrl = "http://192.168.18.29/Test/MyWebsiteImages/2013_07_to7szt75poNC/760x760/" + ct_name; //这里只是把服务器上的图片路径写死了
fileUrl[count] = imageUrl;
ct_detail_name = json_data.getString("filename");
imageDetailUrl = "http://192.168.18.29/Test/MyWebsiteImages/2013_07_to7szt75poNC/760x760/"
+ ct_detail_name;
detailUrl[count] = imageDetailUrl;
count++;

}
} catch (JSONException e1) {
e1.printStackTrace();
} catch (ParseException e1) {
e1.printStackTrace();
}

setupViews();

}

private void setupViews() {
mListview = (ListView) findViewById(R.id.main_lv_list);
adapter = new MyAdapter(fileUrl, count, this);//这里把从数据库读取出来的图片URL传给Adapter
mListview.setAdapter(adapter);
mListview.setOnScrollListener(mScrollListener);
// 添加ListView中Item的点击事件，针对整个Item，如果Item布局不同的组件，对不同的组件添加不同的事件，刚要另外处理，我实现了这个功能，这里就不多说，可以自己再找资料研究。
mListview.setOnItemClickListener(new OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
setTitle("点击第" + arg2 + "列" );

// bitmap = getBitmap(detailUrl[arg2]);
//
// buff = Bitmap2Bytes(bitmap);
// Intent mIntent = new Intent();
// mIntent.putExtra("image", buff);
// mIntent.setClass(ZhiXunActivity.this,
// ZhiXunDetailActivity.class);
// startActivity(mIntent);
}
});
}

OnScrollListener mScrollListener = new OnScrollListener() {//加载图片的缓存处理

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
switch (scrollState) {
case OnScrollListener.SCROLL_STATE_FLING:
adapter.setFlagBusy(true);
break;
case OnScrollListener.SCROLL_STATE_IDLE:
adapter.setFlagBusy(false);
break;
case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
adapter.setFlagBusy(false);
break;
default:
break;
}
adapter.notifyDataSetChanged();
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

}
};
}

ImageLoader .java:

public class ImageLoader {
private static final String TAG = "ImageLoader";
private static final int MAX_CAPACITY = 10;// 一级缓存的最大空间
private static final long DELAY_BEFORE_PURGE = 10 * 1000;// 定时清理缓存

// 0.75是加载因子为经验值，true则表示按照最近访问量的高低排序，false则表示按照插入顺序排序
private HashMap<String, Bitmap> mFirstLevelCache = new LinkedHashMap<String, Bitmap>(MAX_CAPACITY / 2, 0.75f, true) {
private static final long serialVersionUID = 1L;

protected boolean removeEldestEntry(Entry<String, Bitmap> eldest) {
if (size() > MAX_CAPACITY) {// 当超过一级缓存阈值的时候，将老的值从一级缓存搬到二级缓存
mSecondLevelCache.put(eldest.getKey(), new SoftReference<Bitmap>(eldest.getValue()));
return true;
}
return false;
};
};
// 二级缓存，采用的是软应用，只有在内存吃紧的时候软应用才会被回收，有效的避免了oom
private ConcurrentHashMap<String, SoftReference<Bitmap>> mSecondLevelCache = new ConcurrentHashMap<String, SoftReference<Bitmap>>(
MAX_CAPACITY / 2);

// 定时清理缓存
private Runnable mClearCache = new Runnable() {
@Override
public void run() {
clear();
}
};
private Handler mPurgeHandler = new Handler();

// 重置缓存清理的timer
private void resetPurgeTimer() {
mPurgeHandler.removeCallbacks(mClearCache);
mPurgeHandler.postDelayed(mClearCache, DELAY_BEFORE_PURGE);
}

/**
* 清理缓存
*/
private void clear() {
mFirstLevelCache.clear();
mSecondLevelCache.clear();
}

/**
* 返回缓存，如果没有则返回null
*
* @param url
* @return
*/
public Bitmap getBitmapFromCache(String url) {
Bitmap bitmap = null;
bitmap

补充：移动开发 , Android ,