当使用back按钮时，碎片并不总是被替换。
当使用back按钮时，碎片并不总是被替换。
提问于 2013-07-13 14:47:21
我使用actionbar选项卡，因为我需要导航元素在每个页面上。我使用ActionBarSherlock来实现向后兼容性(最低API 8，目标API 17)。我的MainActivity扩展了SherlockFragmentActivity。在我的onCreate()里，我有
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(true);
Tab tab1 = actionBar.newTab().setText("My Pages")
.setTabListener(new MyPagesFragment());
Tab tab2 = actionBar.newTab().setText("Search")
.setTabListener(new SearchFragment());
Tab tab3 = actionBar.newTab().setText("About")
.setTabListener(new AboutFragment());
// Start with the second tab selected.
actionBar.addTab(tab1, 0, false);
actionBar.addTab(tab2, 1, true);
actionBar.addTab(tab3, 2, false);所有选项卡片段都是实现ActionBar.TabListener的SherlockListFragments，并执行以下操作
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.replace(android.R.id.content, this, "mypages");
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(this);
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// Force a complete reload.
onTabSelected(tab, ft);
}搜索页有一个EditText，并在AsyncTask中使用它的值从API中获取数据并将其添加到SQLite数据库中，然后调用
((MainActivity) getActivity()).showDetailView(responseCode);要显示详细信息，这是我的MainActivity中的一个方法，如下所示：
protected void showDetailView(long codeID) {
SherlockFragment detailFragment = new DetailFragment();
Bundle args = new Bundle();
args.putLong("codeID", codeID);
detailFragment.setArguments(args);
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.replace(android.R.id.content, detailFragment);
ft.addToBackStack(null);
ft.commit();
}DetailFragment是一个使用getArguments()检索代码is的SherlockFragment --
Bundle args = getArguments();
if (null != args) {
codeRowID = args.getLong("codeID");
}-从数据库中读取匹配的数据以显示它。所述数据通常包含指向更多详细信息的链接，单击将导致新的showDetailView再次调用codeID的链接。
MyPages是所有缓存的详细信息页的列表，它也调用showDetailView：
@Override
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
((MainActivity) getActivity()).showDetailView(pages[position].codeId);
}展望未来，这似乎很好。然而，当我使用“后退”按钮时，碎片有时会停留在周围，所以在恢复的片段后面仍然可以看到它们。我怎样才能阻止这种情况的发生？
我认为问题可能是标签没有被添加到后台？但是当我尝试这样做时，他们会抛出一个异常，告诉我不能将它们添加到后台，所以我不明白您应该如何处理这个问题。我不明白为什么这个东西看起来应该是很多人想要做的非常基本的导航功能--我见过的每一个android手机和桌子上都有后退键，无论是物理上还是软件上！--显然没有已知的解决方案。我只是从根本上误解了它们的使用吗？在这种情况下不应该使用碎片吗？否则，如何在不重复每个页面上相同的代码的情况下执行持久导航元素？
日志-启动程序-
07-20 23:33:49.521: D/NAVIGATION_TRACE(7425): MAIN - onCreate
07-20 23:33:50.013: D/NAVIGATION_TRACE(7425): SEARCH - onTabSelected
07-20 23:33:50.021: D/NAVIGATION_TRACE(7425): SEARCH - onCreateView
07-20 23:33:50.060: D/NAVIGATION_TRACE(7425): SEARCH - onActivityCreated
07-20 23:33:50.060: D/NAVIGATION_TRACE(7425): MAIN - onResume搜索现在可见。搜索一个可以显示细节视图的项目-
07-20 23:34:52.123: D/NAVIGATION_TRACE(7425): SEARCH - handleResponseCode
07-20 23:34:52.123: D/NAVIGATION_TRACE(7425): MAIN - showDetailView - 31细节可见；搜索完毕。单击mypages选项卡-
07-20 23:35:37.787: D/NAVIGATION_TRACE(7425): SEARCH - onTabUnselected
07-20 23:35:37.787: D/NAVIGATION_TRACE(7425): MYPAGES - onTabSelected
07-20 23:35:37.826: D/NAVIGATION_TRACE(7425): MYPAGES - onCreateView
07-20 23:35:37.873: D/NAVIGATION_TRACE(7425): MYPAGES - onActivityCreatedMyPages现在可见；细节消失了。点击上一个按钮-
07-20 23:36:12.130: D/NAVIGATION_TRACE(7425): SEARCH - onCreateView
07-20 23:36:12.201: D/NAVIGATION_TRACE(7425): SEARCH - onActivityCreated搜索和MyPages现在都显示。
MainActivity：
public class MainActivity extends SherlockFragmentActivity
{
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
Log.d("NAVIGATION_TRACE", "MAIN - onCreate");
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(true);
Tab tab1 = actionBar.newTab().setText("My Pages")
.setTabListener(new TabListener<MyPagesFragment>(
this, "mypages", MyPagesFragment.class));
Tab tab2 = actionBar.newTab().setText("Search")
.setTabListener(new TabListener<SearchFragment>(
this, "search", SearchFragment.class));
Tab tab3 = actionBar.newTab().setText("About")
.setTabListener(new TabListener<AboutFragment>(
this, "about", AboutFragment.class));
// Start with the second tab selected.
actionBar.addTab(tab1, 0, false);
actionBar.addTab(tab2, 1, true);
actionBar.addTab(tab3, 2, false);
}
@Override
public void onBackPressed()
{
FragmentManager fm = getSupportFragmentManager();
if (0 < fm.getBackStackEntryCount())
{
super.onBackPressed();
} else {
// prompt to quit
AlertDialog.Builder alertErrorResponse = new AlertDialog.Builder(this);
alertErrorResponse.setMessage("Close app?");
alertErrorResponse.setNegativeButton("Cancel", null);
alertErrorResponse.setPositiveButton("OK", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which)
{
finish();
}
});
alertErrorResponse.show();
}
}
public void showDetailView(long codeID) {
Log.d("NAVIGATION_TRACE", "MAIN - showDetailView - "+String.valueOf(codeID));
lastShownCode = codeID;
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
SherlockFragment detailFragment = new DetailFragment();
Bundle args = new Bundle();
args.putLong("codeID", codeID);
detailFragment.setArguments(args);
ft.replace(android.R.id.content, detailFragment, "details");
ft.addToBackStack(null);
ft.commit();
}
public class TabListener<T extends SherlockListFragment> implements ActionBar.TabListener
{
private final SherlockFragmentActivity mActivity;
private final String mTag;
private final Class<T> mClass;
private SherlockListFragment mFragment;
public TabListener (SherlockFragmentActivity activity, String tag, Class<T> clz)
{
Log.d("NAVIGATION_TRACE", "TabListener - "+tag+" - "+clz.getCanonicalName());
mActivity = activity;
mTag = tag;
mClass = clz;
FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
mFragment = (SherlockListFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached())
{
Log.d("NAVIGATION_TRACE", "DETACH - "+mTag);
removeDetail(ft);
ft.detach(mFragment);
}
ft.commit();
}
public void clearBackStack()
{
Log.d("NAVIGATION_TRACE", "clearBackStack - "+mTag);
FragmentManager fm = mActivity.getSupportFragmentManager();
if (null != fm && 0 < fm.getBackStackEntryCount())
{
fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft)
{
Log.d("NAVIGATION_TRACE", "onTabSelected - "+mTag);
clearBackStack();
ft = mActivity.getSupportFragmentManager().beginTransaction();
if (mFragment == null)
{
Log.d("NAVIGATION_TRACE", "ADD/SHOW - "+mClass.getName());
removeDetail(ft);
mFragment = (SherlockListFragment) SherlockListFragment.instantiate(mActivity, mClass.getName());
ft.add(android.R.id.content, mFragment, mTag);
ft.commit();
}
else
{
Log.d("NAVIGATION_TRACE", "ATTACH/SHOW - "+mClass.getName());
removeDetail(ft);
ft.attach(mFragment);
ft.show(mFragment);
ft.commit();
}
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft)
{
Log.d("NAVIGATION_TRACE", "onTabUnselected - "+mTag);
ft = mActivity.getSupportFragmentManager().beginTransaction();
if (null != mFragment)
{
Log.d("NAVIGATION_TRACE", "HIDE/DETACH - "+mTag);
removeDetail(ft);
ft.hide(mFragment);
ft.detach(mFragment);
ft.commitAllowingStateLoss();
}
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
public void removeDetail(FragmentTransaction ft) {
SherlockFragment detailFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag("details");
if (null != detailFragment && !detailFragment.isDetached()) {
Log.d("NAVIGATION_TRACE", "DETACH - details");
ft.detach(detailFragment);
}
}
}
}示例片段- MyPagesFragment：
public class MyPagesFragment extends SherlockListFragment implements
OnItemClickListener
{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
Log.d("NAVIGATION_TRACE", "MYPAGES - onCreateView");
View view = inflater.inflate(R.layout.mypages, null);
// code to set up list adapter here
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d("NAVIGATION_TRACE", "MYPAGES - onActivityCreated");
getListView().setOnItemClickListener(this);
}
@Override
public void onItemClick(AdapterView<?> parent, View v, int position, long id)
{
Log.d("NAVIGATION_TRACE", "MYPAGES - onItemClick");
((MainActivity) getActivity()).showDetailView(pages[position].codeId);
}
}DetailFragment
public class DetailFragment extends SherlockFragment implements
OnItemClickListener
{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.detail, null);
// bunch of display / list set up code goes here
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
lvLinks.setOnItemClickListener(this);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
// Details page can open other details pages:
((MainActivity) getActivity()).showDetailView(pages[position].id);
}
}注意:添加的更改是根据Sheldon的回答进行的(他似乎已经删除了他们的答案和评论)，这就是为什么TabListener代码在原始部分和后面发布的代码之间进行更改的原因。
目前，我已经黑出了一个解决方案，方法是清空每个选项卡选择的背靠背，并将顶部选项卡视为退出应用程序请求，这是可以的，但我真的希望用户能够在可能的情况下继续在选项卡上进行备份(因为那样的话，如果我有五个详细信息页深，并且我停下来快速搜索一些原来不存在的内容，我可以返回到这些详细信息页面，并继续查找一个或多个细节链接)。
回答 1
Stack Overflow用户
发布于 2013-07-25 10:08:42
试试这个..。
FragmentManager manager = getSupportFragmentManager();
if (manager.getBackStackEntryCount() > 0)
getSupportFragmentManager().popBackStack();
else
finish();页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/17631247
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