我正在尝试在onSaveInstanceState
中保存片段状态,但是当我回到片段时,它总是重新加载而不是从上一个状态开始。
我查看了onCreateView
和onActivityCreated
,并且onSaveInstanceState
始终为空。
public void navigateFragment(String tag, Fragment fragment,
boolean shouldAdd) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if (shouldAdd)
mStacks.get(tag).push(fragment); // push fragment on stack
ft.replace(android.R.id.tabcontent, fragment);
if (shouldAdd)
ft.addToBackStack(tag);
ft.commit();
}
由于我无法使用backstack
,因为在标签页中,堆栈无效。任何帮助都将受到高度赞赏。
答案 0 :(得分:6)
在这种情况下,你必须管理片段'自己陈述。我不确切知道你的代码是如何工作的,所以我唯一能做的就是给你一些提示。
您需要实现的第一件事是保存片段的状态。让我们假设所有片段都有唯一的ID。在这种情况下,您需要创建一个将保留所有状态的地图:
private final Map<String, Fragment.SavedState> mFragmentStates = new HashMap<>();
private void saveFragmentState(String id, Fragment fragment) {
Fragment.SavedState fragmentState =
getSupportFragmentManager().saveFragmentInstanceState(fragment);
mFragmentStates.put(id, fragmentState);
}
您需要为要删除的片段调用此方法。然后我们需要恢复片段的状态以及我们如何做到这一点:
private void restoreFragmentState(String id, Fragment fragment) {
Fragment.SavedState fragmentState = mFragmentStates.remove(id);
if (fragmentState != null) {
fragment.setInitialSavedState(savedState);
}
}
在向事务添加片段之前需要调用此方法。
提供的代码应该可以正常工作,但要使其在活动娱乐上正常工作,我们需要正确保存和恢复mFragmentStates
:
private static final String KEY_FRAGMENT_STATES = "fragment_states";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/* Your code ... */
if (savedInstanceState != null) {
Bundle fragmentStates =
savedInstanceState.getParcelable(KEY_FRAGMENT_STATES);
if (fragmentStates != null) {
for (String id : fragmentStates.keySet()) {
Fragment.SavedState fragmentState =
fragmentStates.getParcelable(id);
mFragmentStates.put(id, fragmentState);
}
}
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
/* Your code ... */
Bundle fragmentStates = new Bundle(mFragmentStates.size());
for (Map.Entry<String, Fragment.SavedState> entry : mFragmentStates.entrySet()) {
fragmentStates.put(entry.getKey(), entry.getValue());
}
outState.putParcelable(KEY_FRAGMENT_STATES, fragmentStates);
}
您也可以查看FragmentStatePagerAdapter课程。它使用相同的方法来管理ViewPager
的片段的状态。
更新:所以你的代码应该看起来像这样:
private Fragment mCurrentFragment;
public void navigateFragment(String tag, Fragment fragment,
boolean shouldAdd) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
if (shouldAdd) {
mStacks.get(tag).push(fragment); // push fragment on stack
}
if (mCurrentFragment != null) {
saveFragmentState(mCurrentFragment.getClass().getName(), mCurrentFragment);
}
mCurrentFragment = fragment;
restoreFragmentState(fragment.getClass().getName(), fragment);
transaction.replace(android.R.id.tabcontent, fragment);
if (shouldAdd) {
// You shouldn't use back-stack when managing fragment states by yourself.
transaction.addToBackStack(tag);
}
transaction.commit();
}
在这个例子中,我使用片段的类名作为id,因此所有片段必须具有不同的类。但您可以使用任何其他唯一值作为ID。另外一件重要的事情是,在自己管理片段状态时,不应该使用反向堆栈。 Back-stack执行类似的状态管理,您可能会遇到冲突。
答案 1 :(得分:0)
我认为您应该使用共享首选项的概念,这比使用本地文件或数据库更快,并且更容易编码。一个很好的Android网页@ Storage Options。我会从网页上添加一些示例代码并更改一些以满足您的需求。
首先,在onCreate()覆盖方法中获取从首选项中保存的数据:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
boolean silent = settings.getBoolean("silentMode", false);
...
}
接下来让我们在片段停止或退出之前保存数据,原因有多种。通过覆盖onDetach
方法实现此目的,网页覆盖onStop()
代替。
@Override
public void onDetach() {
super.onDetach();
...
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putBoolean("silentMode", mSilentMode);
// Commit the edits!
editor.commit();
}
祝你好运,玩得开心!
答案 2 :(得分:0)
你正在做替换片段,这就是片段被破坏的原因。你可以尝试下面。在这里,我在单个 FragmentTransaction 中做了两件事,我添加一个新片段&amp; 隐藏现有片段。
假设我们在片段 A
上添加片段 B FragmentTransaction ft = fragmentManager.beginTransaction();
ft.add(android.R.id.tabcontent, fragmentB, tagFragmentB)
.hide(fragmentManager.findFragmentByTag(tagFragmentA))
.addToBackStack(tag)
.commit();
按下后,删除片段 B &amp; 显示具有相同状态的片段 A (在添加片段 B 之前)
请注意 tagFragmentA &amp; tagFragmentB 是片段 A &amp;分别添加 B
答案 3 :(得分:0)
我不清楚你用来实现Tabs的方式。 我猜,
ft.replace(android.R.id.tabcontent, fragment);
你可能已经实现了FragmentTabHost。
编写customFragmentTabhost并覆盖
@Override
public void onTabChanged(String tabId) {
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
if (tabId.equals(“Tab1”)) {
TabFragment1 fragment1 = null;
if (getSupportFragmentManager().findFragmentByTag(“Tab1”) == null) {
fragment1 = new TabFragment1();
} else {
fragment1 = (TabFragment1) getSupportFragmentManager().findFragmentByTag("Tab1");
}
t.replace(R.id.realContent, fragment1, "Tab1").addToBackStack(null).commit();
}
}
<强>更新强>
确保未在方向上重新创建活动,如果是这样,则设置为setRetainInstance(true),这样即使在方向更改时重新创建活动,也会保留碎片。
请为片段中的任何视图提供id。 Android系统维护状态非常重要。
答案 4 :(得分:0)
clearBackStackEntry();
rl.setVisibility(View.GONE);
getSupportFragmentManager().beginTransaction()
.replace(FRAGMENT_CONTAINER, new HomeScreen())
.addToBackStack(null).commit();
private void clearBackStackEntry() {
int count = getSupportFragmentManager().getBackStackEntryCount();
if (count > 0) {
getSupportFragmentManager().popBackStack(null,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}
TRY THIS AND One more for fragment also try this: but use support.v4.app.Fragment, May be it will help you
Fragment fr = new main();
android.support.v4.app.FragmentTransaction fragmentTransaction = getFragmentManager()
.beginTransaction();
fragmentTransaction.replace(R.id.fragment_place, fr);
fragmentTransaction.commit();
// getActivity().finish();
答案 5 :(得分:0)
声明
setRetainInstance(true)
在你的片段onCreate()中。重建以前的状态
链接有助于理解setRetainInstance的工作方式。
Understanding Fragment's setRetainInstance(boolean)
Why use Fragment#setRetainInstance(boolean)?
谢谢:)
答案 6 :(得分:0)
处理这些事情非常简单。我可以给你样品来处理我们添加的Fr代理的背压。
我已经声明了一个片段堆栈并将其中的所有片段推送到其中;
public static Stack<Fragment> fragmentStack;
制作一个这样的方法:
public static void replaceFragementsClick(Fragment fragementObj, Bundle bundleObj, String title){
try {
FragmentManager fragmentManager = ((FragmentActivity) mContext).getSupportFragmentManager();
if (fragementObj != null) {
fragementObj.setArguments(bundleObj);
fragmentManager.beginTransaction().replace(R.id.frame_container, fragementObj).commit();
}
DashBoardActivity.fragmentStack.push(fragementObj);
} catch (Exception e) {
e.printStackTrace();
}
}
也尝试这个:
public static void replaceFragementsClickBack(Fragment fragementObj, Bundle bundleObj, String title){
try {
FragmentManager fragmentManager = ((FragmentActivity) mContext).getSupportFragmentManager();
if (fragementObj != null) {
fragementObj.setArguments(bundleObj);
fragmentManager.beginTransaction().replace(R.id.frame_container, fragementObj).commit();
DashBoardActivity.fragmentStack.pop();
}
} catch (Exception e) {
e.printStackTrace();
}
}
在您添加的基本活动中,覆盖背景,如:
@Override
public void onBackPressed() {
/**
* Do Current Fragment Pop
* */
fragmentStack.pop();
if(fragmentStack.size() >0){
Bundle bunldeObj = new Bundle();
//******Exit from Current Fragment
Fragment fragment = fragmentStack.pop();
// fragmentStack.push(fragment);
if(fragment instanceof PhotosFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Photos");
}else if(fragment instanceof PhotoDetatilFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Photos");
}else if(fragment instanceof PhotoFullViewFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Photos");
}else if(fragment instanceof HomeFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Home");
}else if(fragment instanceof VideosFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Videos");
}else if(fragment instanceof VideoDetailFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Videos");
}else if(fragment instanceof VideoViewFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Videos");
}else if(fragment instanceof MusicFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Music");
}else if(fragment instanceof MusicListFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Music");
}else if(fragment instanceof InstallAppsFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Apps");
}else if(fragment instanceof MessageFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Messages");
}else if(fragment instanceof MessageDetailFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Messages");
}else if(fragment instanceof LocateDeviceFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Locate Device");
}else if(fragment instanceof FilesFragmentBottomBar){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Files");
}else if(fragment instanceof AppsFragment){
bunldeObj.putString("position", "4");
replaceFragementsClick(fragment,bunldeObj,"Apps");
}else {
super.onBackPressed();
Intent intent = new Intent(DashBoardActivity.this,ConnectDeviceActivity.class);
startActivity(intent);
finish();
}
}