问题
This is a followup to this question: Android - why is this telling me "Content view not yet created"?
So, the following code throws an error:
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LinearLayout Layout5 = (LinearLayout) inflater.inflate(R.layout.tab_frag5_layout, container, false);
Cursor allBands;
MyDatabase db;
Context ctx = (Context)TabFragment5.this.getActivity();
db = new MyDatabase(ctx);
allBands = db.getBands();
ListAdapter adapter = new SimpleCursorAdapter (ctx,
R.layout.listelement,
allBands,
new String[] {"BandName"},
new int[] {R.id.text15});
getListView().setAdapter(adapter);
return Layout5;
}
BUT, if i add a button to the layout and place the code inside the OnClick method, it works perfectly. Like this:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LinearLayout Layout5 = (LinearLayout) inflater.inflate(R.layout.tab_frag5_layout, container, false);
// Register for the Button.OnClick event
Button bShop = (Button)Layout5.findViewById(R.id.button_test);
bShop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Cursor allBands;
MyDatabase db;
Context ctx = (Context)TabFragment5.this.getActivity();
db = new MyDatabase(ctx);
allBands = db.getBands();
ListAdapter adapter = new SimpleCursorAdapter (ctx,
R.layout.listelement,
allBands,
new String[] {"BandName"},
new int[] {R.id.text15});
getListView().setAdapter(adapter);
}
});
return Layout5;
Why does this happen. i understand it must have something to do with the fragments lifecycle, but what? How can I circumvent this so the list listview is populated when the fragment opens, and not only when i click the button?
Thanks
EDIT: this is the main activity
public class TabsFragmentActivity extends FragmentActivity implements TabHost.OnTabChangeListener {
private TabHost mTabHost;
private HashMap mapTabInfo = new HashMap();
private 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;
/**
* @param context
*/
public TabFactory(Context context) {
mContext = context;
}
/** (non-Javadoc)
* @see android.widget.TabHost.TabContentFactory#createTabContent(java.lang.String)
*/
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
/** (non-Javadoc)
* @see android.support.v4.app.FragmentActivity#onCreate(android.os.Bundle)
*/
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Step 1: Inflate layout
setContentView(R.layout.tabs_layout);
// Step 2: Setup TabHost
initialiseTabHost(savedInstanceState);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab")); //set the tab as per the saved state
}
}
/** (non-Javadoc)
* @see android.support.v4.app.FragmentActivity#onSaveInstanceState(android.os.Bundle)
*/
protected void onSaveInstanceState(Bundle outState) {
outState.putString("tab", mTabHost.getCurrentTabTag()); //save the tab selected
super.onSaveInstanceState(outState);
}
/**
* Step 2: Setup TabHost
*/
private void initialiseTabHost(Bundle args) {
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
TabInfo tabInfo = null;
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab1").setIndicator("s1"), ( tabInfo = new TabInfo("Tab1", TabFragment1.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab2").setIndicator("s2"), ( tabInfo = new TabInfo("Tab2", TabFragment2.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab3").setIndicator("s3"), ( tabInfo = new TabInfo("Tab3", TabFragment3.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab4").setIndicator("s4"), ( tabInfo = new TabInfo("Tab4", TabFragment4.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab5").setIndicator("s5"), ( tabInfo = new TabInfo("Tab5", TabFragment5.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab6").setIndicator("s6"), ( tabInfo = new TabInfo("Tab6", TabFragment6.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
// Default to first tab
this.onTabChanged("Tab1");
//
mTabHost.setOnTabChangedListener(this);
}
/**
* @param activity
* @param tabHost
* @param tabSpec
* @param clss
* @param args
*/
private static void addTab(TabsFragmentActivity 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);
}
/** (non-Javadoc)
9
* @see android.widget.TabHost.OnTabChangeListener#onTabChanged(java.lang.String)
*/
public void onTabChanged(String tag) {
TabInfo newTab = (TabInfo) this.mapTabInfo.get(tag);
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();
}
}
}
And the fragment XML
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/mylayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#D6D6D6"
>
<Button
android:id="@+id/button_test"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0"
android:text="Button" />
<ListView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="0"
android:id="@android:id/list"></ListView>
回答1:
The key here is when setAdapter() is being called inside your ListFragment.
In your first example, setAdapter() was being called inside onCreateView() which won't work because the ListFragment checks to ensure there is a list defined in your layouts before allowing the adapter to be set and until onCreateView() returns the view you are creating, there isn't a layout to check. It's a chicken and egg problem.
The reason the second example works is because you aren't actually callnig setAdapter() from within onCreateView(). The adapter isn't set until the button is clicked in your resulting layout.
The basic issue here is that fragments differ from activities in that you can't do the same sorts of things in onCreate() as you are used to doing with your activities, especially when it comes to setting up your adapters.
回答2:
Do you extend the Fragment Class or the ListFragment? This is how I used it inside a ListFragment ->
public class FooFragment extends ListFragment{
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_eventlist, null);
eventAdapter = new EventAdapter(getActivity(), R.layout.list_item_event, events);
setListAdapter(eventAdapter);
return root;
}
}
Edit:
Just modify the variables and types:
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_activitystream, null);
return root;
}
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
states = new ArrayList<Status>();
...
YourAdapter asa = new YourAdapter(getActivity(), R.layout.list_item_status, states);
setListAdapter(asa);
Log.i(TAG, "onCreate is done");
}
来源：https://stackoverflow.com/questions/9297151/android-why-is-this-happening-content-not-yet-created-error