我使用此处提供的示例代码将导航选项卡添加到操作栏:
http://developer.android.com/guide/topics/ui/actionbar.html我正在使用ActionBarSherlock。
我的TabListener是直接从文档中复制的。
public static class TabListener<T extends Fragment> implements ActionBar.TabListener {
private Fragment mFragment;
private final Activity mActivity;
private final String mTag;
private final Class<T> mClass;
/** Constructor used each time a new tab is created.
* @param activity The host Activity, used to instantiate the fragment
* @param tag The identifier tag for the fragment
* @param clz The fragment's Class, used to instantiate the fragment
*/
public TabListener(Activity activity, String tag, Class<T> clz) {
mActivity = activity;
mTag = tag;
mClass = clz;
}
/* The following are each of the ActionBar.TabListener callbacks */
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
// Check if the fragment is already initialized
if (mFragment == null) {
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
ft.add(android.R.id.content, mFragment, mTag);
} else {
// If it exists, simply attach it in order to show it
ft.attach(mFragment);
}
}
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
if (mFragment != null) {
// Detach the fragment, because another one is being attached
ft.detach(mFragment);
}
}
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
// User selected the already selected tab. Usually do nothing.
}
}
我在 Activity 中设置了监听器:
ActionBar.Tab tab = actionBar.newTab();
tab.setText(getString(R.string.TAB_CALC));
tab.setTabListener(new TabListener<StrokeSelectorFragment>(this, "blah", StrokeSelectorFragment.class));
actionBar.addTab(tab);
但是应用程序因空指针异常而崩溃,因为将空FragmentTransaction传递给了监听器中的onTabSelected()。我应该在某个地方创建一个吗?
我遍历了文档,我很困惑。你能看到我错过的东西吗?
最佳答案
我发现上述Ollie的帖子很有帮助,但不够详尽。我设法重构了ActionBar Guide中提供的代码,如下所示(注意:您必须对TabListener中实现的其他方法进行相同的更改):
public void onTabSelected(Tab tab, FragmentTransaction ignoredFt) {
FragmentManager fragMgr = ((FragmentActivity)mActivity).getSupportFragmentManager();
FragmentTransaction ft = fragMgr.beginTransaction();
// Check if the fragment is already initialized
if (mFragment == null) {
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
ft.add(android.R.id.content, mFragment, mTag);
} else {
// If it exists, simply attach it in order to show it
ft.attach(mFragment);
}
}
关于android - 空FragmentTransaction传递给TabListener.onTabSelected(),我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/8645549/