android-ibc-forum

commit 6566f1c5a04321d6a063662da6a34dbd8032094e
parent 4c27688126ad528f892a9e7ef958a7a3c6b8371c
Author: Jan Dankert <devnull@localhost>
Date:   Wed, 25 Jan 2012 23:33:09 +0100

Basisklasse für Activitys mit seitenweisen Listen.

Diffstat:
src/de/mtbnews/android/EndlessListActivity.java
 | 
142
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 142 insertions(+), 0 deletions(-)
diff --git a/src/de/mtbnews/android/EndlessListActivity.java b/src/de/mtbnews/android/EndlessListActivity.java
@@ -0,0 +1,142 @@
+/**
+ * 
+ */
+package de.mtbnews.android;
+
+import java.util.List;
+
+import android.app.ListActivity;
+import android.content.SharedPreferences;
+import android.preference.PreferenceManager;
+import android.widget.AbsListView;
+import android.widget.BaseAdapter;
+import android.widget.ListView;
+import android.widget.AbsListView.OnScrollListener;
+
+/**
+ * Erweitert die Oberklasse {@link ListActivity} für "endlose" Listen, die
+ * seitenweise vom Server geladen werden. Bei Erreichen des Endes wird
+ * automatisch der nächste Bereich nachgeladen.
+ * 
+ * @author dankert
+ * 
+ */
+public abstract class EndlessListActivity<T> extends ListActivity
+{
+	private boolean loadingMore = true;
+
+	private int displayFrom;
+	private int displayTo;
+
+	private SharedPreferences prefs = PreferenceManager
+			.getDefaultSharedPreferences(this);
+
+	/**
+	 * Absolute Anzahl aller verfügbaren Elemente.
+	 * 
+	 * @return Anzahl
+	 */
+	protected abstract int getTotalSize();
+
+	protected void initialLoad()
+	{
+		final int numLoad = Integer.parseInt(prefs.getString("num_load", "10"));
+		final boolean autoScrollDown = prefs.getBoolean("scroll_down", false);
+
+		if (autoScrollDown)
+		{
+			loadEntries(0, 1, true);
+
+			int end = getTotalSize();
+			int start = Math.max(0, end - numLoad);
+
+			loadEntries(start, end, true);
+
+			displayFrom = start;
+			displayTo = end;
+		}
+		else
+		{
+			int start = 0;
+			int end = numLoad - 1;
+
+			List<T> entries = loadEntries(start, end, true);
+			displayFrom = start;
+			displayTo = start + entries.size() - 1;
+		}
+
+		((BaseAdapter) getListAdapter()).notifyDataSetChanged();
+	}
+
+	/**
+	 * @param from
+	 * @param to
+	 * @param firstLoad
+	 * @return gelandene Elemente
+	 */
+	abstract protected List<T> loadEntries(int from, int to, boolean firstLoad);
+
+	protected void setOnScrollListener()
+	{
+		final ListView list = getListView();
+
+		/**
+		 * Weitere List-Einträge automatisch nachladen.
+		 */
+		list.setOnScrollListener(new OnScrollListener()
+		{
+			@Override
+			public void onScrollStateChanged(AbsListView view, int scrollState)
+			{
+			}
+
+			/**
+			 * Callback method to be invoked when the list or grid has been
+			 * scrolled. This will be called after the scroll has completed
+			 * Parameters
+			 * 
+			 * @param view
+			 *            The view whose scroll state is being reported
+			 * @param firstVisibleItem
+			 *            the index of the first visible cell (ignore if
+			 *            visibleItemCount == 0)
+			 * @param visibleItemCount
+			 *            the number of visible cells
+			 * @param totalItemCount
+			 *            the number of items in the list adaptor {@inheritDoc}
+			 * 
+			 * @see android.widget.AbsListView.OnScrollListener#onScroll(android.widget.AbsListView,
+			 *      int, int, int)
+			 */
+			@Override
+			public void onScroll(AbsListView view, int firstVisibleItem,
+					int visibleItemCount, int totalItemCount)
+			{
+
+				// Letztes Item, dass angezeigt wird.
+				int lastInScreen = firstVisibleItem + visibleItemCount;
+
+				// is the bottom item visible & not loading more already ? Load
+				// more !
+				if ((lastInScreen == totalItemCount)
+						&& (totalItemCount < getTotalSize()) && !(loadingMore))
+				{
+					loadingMore = true;
+
+					int start = displayTo + 1;
+					int end = start
+							+ Integer.parseInt(prefs
+									.getString("num_load", "10")) - 1;
+
+					displayTo = end;
+
+					loadEntries(start, end, false);
+
+					loadingMore = false;
+					((BaseAdapter) getListAdapter()).notifyDataSetChanged();
+
+				}
+			}
+		});
+	}
+}