android_calculator-47: Remember last used tab in vars, functions etc

src/main/java/org/solovyev/android/view/LastTabSaver.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2009-2012. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.view;
+
+import android.app.TabActivity;
+import android.preference.PreferenceManager;
+import android.widget.TabHost;
+import org.jetbrains.annotations.NotNull;
+import org.solovyev.android.view.prefs.StringPreference;
+
+/**
+ * User: serso
+ * Date: 1/9/12
+ * Time: 6:17 PM
+ */
+public class LastTabSaver implements TabHost.OnTabChangeListener {
+
+	private static final String LAST_OPENED_TAB_P_KEY = "last_opened_tab_";
+
+	@NotNull
+	private final StringPreference<String> preference;
+
+	@NotNull
+	private final TabActivity tabActivity;
+
+	public LastTabSaver(@NotNull TabActivity tabActivity, @NotNull String defaultTabId) {
+		this.tabActivity = tabActivity;
+		this.preference = StringPreference.newInstance(getPreferenceKey(), defaultTabId);
+
+		final TabHost tabHost = tabActivity.getTabHost();
+		tabHost.setCurrentTabByTag(this.getLastOpenedTabId());
+		tabHost.setOnTabChangedListener(this);
+	}
+
+	public void destroy() {
+		final TabHost tabHost = tabActivity.getTabHost();
+		tabHost.setOnTabChangedListener(null);
+	}
+
+	@Override
+	public void onTabChanged(String tabId) {
+		preference.putPreference(PreferenceManager.getDefaultSharedPreferences(tabActivity), tabId);
+	}
+
+	@NotNull
+	public String getLastOpenedTabId() {
+		return preference.getPreference(PreferenceManager.getDefaultSharedPreferences(tabActivity));
+	}
+
+	@NotNull
+	private String getPreferenceKey() {
+		return LAST_OPENED_TAB_P_KEY + tabActivity.getClass().getName();
+	}
+}