我是 ABS（ActionBarSherlock）的新手，有时 ABS 对我来说似乎很复杂。在我看来，ABS 的全部（或大部分）要点是让较旧的机器人（<11）能够运行操作栏。
我需要在操作栏选项卡中使用片段，所以我尝试从片段演示中的“FragmentTabs.java”学习，但令人惊讶的是，我发现这个示例不使用 ABS 操作栏并使用 tabhost。
我的问题是：
为什么实现了tabhost而不是ABS actionbar，而ABS的重点是Actionbar的使用？它与片段的用法不兼容吗？
因为在此示例中片段被定义为静态，所以我如何获得对非静态 tabhost 和 setCurrentTab() 的引用？findViewById() 不起作用，因为片段被定义为静态
3.如何根据代码逻辑在标签之间切换？下面的代码永远不会起作用。getParent()也不起作用。
TabHost tabHost = (TabHost) findViewById(android.R.id.tabhost);
tabHost.setCurrentTab(2);
以下是从 Sherlock 片段演示中提取的代码：
public class FragmentTabs extends SherlockFragmentActivity {
TabHost mTabHost;
TabManager mTabManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
setTheme(SampleList.THEME); // Used for theme switching in samples
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();
}
}
}
}
public class FragmentStackSupport extends SherlockFragmentActivity {
int mStackLevel = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
setTheme(SampleList.THEME); //Used for theme switching in samples
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_stack);
// Watch for button clicks.
Button button = (Button)findViewById(R.id.new_fragment);
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
addFragmentToStack();
}
});
if (savedInstanceState == null) {
// Do first time initialization -- add initial fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.simple_fragment, newFragment).commit();
} else {
mStackLevel = savedInstanceState.getInt("level");
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("level", mStackLevel);
}
void addFragmentToStack() {
mStackLevel++;
// Instantiate a new fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.simple_fragment, newFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
public static class CountingFragment extends SherlockFragment {
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static CountingFragment newInstance(int num) {
CountingFragment f = new CountingFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
return v;
}
}
}