I know the tabactivity thing has been covered here a million times, by ten million people. I’ve got the developer references and have been reading all the threads I can find on SO. My question is though, is fragments REALLY that complicated? From what I can gather, it seems to be, whereas TabActivty was so easy. See example below:
My current code, required for four tabs, looks like this:
Resources res = getResources(); // Resource object to get Drawables
TabHost tabHost = getTabHost(); // The activity TabHost
TabHost.TabSpec spec; // Resusable TabSpec for each tab
Intent intent; // Reusable Intent for each tab
// Create an Intent to launch an Activity for the tab (to be reused)
intent = new Intent().setClass(this, ServerActivity.class);
// Initialize a TabSpec for each tab and add it to the TabHost
spec = tabHost
.newTabSpec("server")
.setIndicator("Server",
res.getDrawable(R.drawable.ic_tab_server))
.setContent(intent);
tabHost.addTab(spec);
// Do the same for the other tabs
intent = new Intent().setClass(this, StatusActivity.class);
spec = tabHost
.newTabSpec("status")
.setIndicator("Status",
res.getDrawable(R.drawable.ic_tab_status))
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, LoggingActivity.class);
spec = tabHost
.newTabSpec("logging")
.setIndicator("Logs",
res.getDrawable(R.drawable.ic_tab_logging))
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, DeliveryActivity.class);
spec = tabHost
.newTabSpec("deliveryqueue")
.setIndicator("Queue", res.getDrawable(R.drawable.ic_tab_queue))
// .setIndicator("Delivery Queue",
// res.getDrawable(R.drawable.ic_tab_artists))
.setContent(intent);
tabHost.addTab(spec);
tabHost.setCurrentTab(2);
}
According to the developers reference, for the equivelent of 4 tabs, you need ALL this:
import java.util.HashMap;
import com.example.android.supportv4.R;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.widget.TabHost;
/**
* This demonstrates how you can implement switching between the tabs of a
* TabHost through fragments. It uses a trick (see the code below) to allow
* the tabs to switch between fragments instead of simple views.
*/
public class FragmentTabs extends FragmentActivity {
TabHost mTabHost;
TabManager mTabManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_tabs);
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mTabManager = new TabManager(this, mTabHost, R.id.realtabcontent);
mTabManager.addTab(mTabHost.newTabSpec("simple").setIndicator("Simple"),
FragmentStackSupport.CountingFragment.class, null);
mTabManager.addTab(mTabHost.newTabSpec("contacts").setIndicator("Contacts"),
LoaderCursorSupport.CursorLoaderListFragment.class, null);
mTabManager.addTab(mTabHost.newTabSpec("custom").setIndicator("Custom"),
LoaderCustomSupport.AppListFragment.class, null);
mTabManager.addTab(mTabHost.newTabSpec("throttle").setIndicator("Throttle"),
LoaderThrottleSupport.ThrottledLoaderListFragment.class, null);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("tab", mTabHost.getCurrentTabTag());
}
/**
* This is a helper class that implements a generic mechanism for
* associating fragments with the tabs in a tab host. It relies on a
* trick. Normally a tab host has a simple API for supplying a View or
* Intent that each tab will show. This is not sufficient for switching
* between fragments. So instead we make the content part of the tab host
* 0dp high (it is not shown) and the TabManager supplies its own dummy
* view to show as the tab content. It listens to changes in tabs, and takes
* care of switch to the correct fragment shown in a separate content area
* whenever the selected tab changes.
*/
public static class TabManager implements TabHost.OnTabChangeListener {
private final FragmentActivity mActivity;
private final TabHost mTabHost;
private final int mContainerId;
private final HashMap<String, TabInfo> mTabs = new HashMap<String, TabInfo>();
TabInfo mLastTab;
static final class TabInfo {
private final String tag;
private final Class<?> clss;
private final Bundle args;
private Fragment fragment;
TabInfo(String _tag, Class<?> _class, Bundle _args) {
tag = _tag;
clss = _class;
args = _args;
}
}
static class DummyTabFactory implements TabHost.TabContentFactory {
private final Context mContext;
public DummyTabFactory(Context context) {
mContext = context;
}
@Override
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
public TabManager(FragmentActivity activity, TabHost tabHost, int containerId) {
mActivity = activity;
mTabHost = tabHost;
mContainerId = containerId;
mTabHost.setOnTabChangedListener(this);
}
public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
tabSpec.setContent(new DummyTabFactory(mActivity));
String tag = tabSpec.getTag();
TabInfo info = new TabInfo(tag, clss, args);
// 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.
info.fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
if (info.fragment != null && !info.fragment.isDetached()) {
FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
ft.detach(info.fragment);
ft.commit();
}
mTabs.put(tag, info);
mTabHost.addTab(tabSpec);
}
@Override
public void onTabChanged(String tabId) {
TabInfo newTab = mTabs.get(tabId);
if (mLastTab != newTab) {
FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
if (mLastTab != null) {
if (mLastTab.fragment != null) {
ft.detach(mLastTab.fragment);
}
}
if (newTab != null) {
if (newTab.fragment == null) {
newTab.fragment = Fragment.instantiate(mActivity,
newTab.clss.getName(), newTab.args);
ft.add(mContainerId, newTab.fragment, newTab.tag);
} else {
ft.attach(newTab.fragment);
}
}
mLastTab = newTab;
ft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
}
}
}
}
Is it REALLY that complex? it’s like two – three times the amount of code to complete the same thing. I really want to stay away from using deprecated methods, but wow.
The developer document’s solution is around 100 lines of additional code (plus a view replacement). The solution provided isn’t particularly complex, and extendable in an obvious location (onTabChanged) if you want to trigger an action when the tab is changed. I wouldn’t shy away from using it as it will obtain the results you so desire. I was moving from an ActionBar to TabHost and found it to be a drop-in replacement for my existing fragments management.