Fragmento do Android oncreateview chamado na alteração de tabulação
Eu tenho trabalhado com o Android por um tempo, mas fragmentos são um pouco novos para mim (como são para a maioria das pessoas provavelmente). De qualquer forma, eu tenho o código abaixo, e funciona bem. Eu tenho três fragmentos, um em cada aba. Eu estou querendo saber se é normal que o onCreateView seja chamado toda vez que eu troco as abas, e faz sentido fazer isso? Não deveria haver uma maneira de não redesenhar o fragmento toda vez que a aba muda?
Estou convertendo isso de um aplicativo que tinha 3 atividades, uma em cada guia, e parece um desperdício recriar a visualização toda vez que a guia muda, quando costumava ficar bem com as visualizações existentes entre as alterações das guias. .
BTW, este código emprestado de:http://thepseudocoder.wordpress.com/2011/10/04/android-tabs-the-fragment-way/
public class Tabs extends FragmentActivity implements
TabHost.OnTabChangeListener {
final String MAP_TAB = "Map";
final String IMAGES_TAB = "Images";
final String SETTINGS_TAB = "Settings";
TabHost mTabHost;
HashMap<String, TabInfo> mapTabInfo = new HashMap<String, TabInfo>();
TabInfo mLastTab = null;
private class TabInfo {
private String tag;
private Class clss;
private Bundle args;
private Fragment fragment;
TabInfo(String tag, Class clazz, Bundle args) {
this.tag = tag;
this.clss = clazz;
this.args = args;
}
}
class TabFactory implements TabContentFactory {
private final Context mContext;
public TabFactory(Context context) {
mContext = context;
}
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
initialiseTabHost(savedInstanceState);
if (savedInstanceState != null)
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab")); //set the tab as per the saved state
}
protected void onSaveInstanceState(Bundle outState) {
outState.putString("tab", mTabHost.getCurrentTabTag()); //save the tab selected
super.onSaveInstanceState(outState);
}
private void initialiseTabHost(Bundle args) {
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
TabInfo tabInfo;
Tabs.addTab(this,
mTabHost,
mTabHost.newTabSpec(MAP_TAB).setIndicator(
MAP_TAB,
getResources().getDrawable(R.drawable.ic_tab_map_states)),
( tabInfo = new TabInfo(MAP_TAB, HMapFragment_NEW.class, args)));
mapTabInfo.put(tabInfo.tag, tabInfo);
Tabs.addTab(this,
mTabHost,
mTabHost.newTabSpec(IMAGES_TAB).setIndicator(
IMAGES_TAB,
getResources().getDrawable(R.drawable.ic_tab_gallery_states)),
( tabInfo = new TabInfo(IMAGES_TAB, ImageGridFragment.class, args)));
mapTabInfo.put(tabInfo.tag, tabInfo);
Tabs.addTab(this,
mTabHost,
mTabHost.newTabSpec(SETTINGS_TAB).setIndicator(
SETTINGS_TAB,
getResources().getDrawable(R.drawable.ic_tab_settings_states)),
( tabInfo = new TabInfo(SETTINGS_TAB, SettingsFragment.class, args)));
mapTabInfo.put(tabInfo.tag, tabInfo);
// Default to first tab
this.onTabChanged(MAP_TAB);
mTabHost.setOnTabChangedListener(this);
}
private static void addTab(Tabs activity, TabHost tabHost, TabHost.TabSpec tabSpec, TabInfo tabInfo) {
// Attach a Tab view factory to the spec
tabSpec.setContent(activity.new TabFactory(activity));
String tag = tabSpec.getTag();
// Check to see if we already have a fragment for this tab, probably
// from a previously saved state. If so, deactivate it, because our
// initial state is that a tab isn't shown.
tabInfo.fragment = activity.getSupportFragmentManager().findFragmentByTag(tag);
if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) {
FragmentTransaction ft = activity.getSupportFragmentManager().beginTransaction();
ft.detach(tabInfo.fragment);
ft.commit();
activity.getSupportFragmentManager().executePendingTransactions();
}
tabHost.addTab(tabSpec);
}
public void onTabChanged(String tag) {
TabInfo newTab = this.mapTabInfo.get(tag);
// if they've clicked to change tabs
if (mLastTab != newTab) {
FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();
if (mLastTab != null)
if (mLastTab.fragment != null) ft.detach(mLastTab.fragment);
if (newTab != null) {
if (newTab.fragment == null) {
newTab.fragment = Fragment.instantiate(this, newTab.clss.getName(), newTab.args);
ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
} else ft.attach(newTab.fragment);
}
mLastTab = newTab;
ft.commit();
this.getSupportFragmentManager().executePendingTransactions();
}
}
}