添加列表图片加载栈，添加 httpHelper 类，以后完善

src/com/hippo/ehviewer/network/HttpHelper.java

@@ -0,0 +1,95 @@
+package com.hippo.ehviewer.network;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.UnknownHostException;
+
+import org.apache.http.conn.ConnectTimeoutException;
+
+import com.hippo.ehviewer.DiskCache;
+import com.hippo.ehviewer.R;
+import com.hippo.ehviewer.util.Ui;
+import com.hippo.ehviewer.util.Util;
+
+import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
+import android.support.v4.util.LruCache;
+import android.util.Log;
+
+/**
+ * It is not thread safe
+ * 
+ * @author Hippo
+ *
+ */
+public class HttpHelper {
+    private static final String TAG = "HttpHelper";
+    
+    private static final String userAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.76 Safari/537.36";
+    private static final int DEFAULT_TIMEOUT = 5 * 1000;
+    
+    private int lastEMsgId = R.string.em_unknown_error;
+    
+    /**
+     * Get last error message id
+     * @return
+     */
+    public int getLastEMsgId() {
+        return lastEMsgId;
+    }
+    
+    public Bitmap getImage(String urlStr, String key,
+            LruCache<String, Bitmap> memoryCache,
+            DiskCache diskCache, boolean getImage) {
+        HttpURLConnection conn = null;
+        Bitmap bitmap = null;
+        try {
+            Log.d(TAG, "Get Image " + urlStr);
+            URL url = new URL(urlStr);
+            conn = (HttpURLConnection)url.openConnection();
+            conn.setRequestProperty("User-Agent", userAgent);
+            conn.setConnectTimeout(DEFAULT_TIMEOUT);
+            conn.setReadTimeout(DEFAULT_TIMEOUT);
+            conn.connect();
+            InputStream is = conn.getInputStream();
+            
+            if (diskCache == null) {
+                if (getImage
+                        && (bitmap = BitmapFactory.decodeStream(is, null, Ui.getBitmapOpt())) != null) {
+                    if (memoryCache != null)
+                        memoryCache.put(key, bitmap);
+                }
+            } else {
+                diskCache.put(key, is);
+                if (memoryCache != null || getImage) {
+                    Bitmap bmp = (Bitmap)diskCache.get(key, Util.BITMAP);
+                    if (bmp != null) {
+                        if (memoryCache != null)
+                            memoryCache.put(key, bmp);
+                        if (getImage)
+                            bitmap = bmp;
+                    }
+                }
+            }
+        } catch (MalformedURLException e) {
+            lastEMsgId = R.string.em_url_error;
+            e.printStackTrace();
+        } catch (ConnectTimeoutException e) {
+            lastEMsgId = R.string.em_timeout;
+            e.printStackTrace();
+        } catch (UnknownHostException e) {
+            lastEMsgId = R.string.em_no_network_2;
+            e.printStackTrace();
+        } catch (IOException e) {
+            lastEMsgId = R.string.em_network_error;
+            e.printStackTrace();
+        } finally {
+            if (conn != null)
+                conn.disconnect();
+        }
+        return bitmap;
+    }
+}