我现在正在构建一个 Android 应用程序，如果在给定场景（非常具体）之后按下 Home 按钮或锁定屏幕，我的应用程序会因错误而崩溃：
10-26 13:57:50.132: E/AndroidRuntime(8663): FATAL EXCEPTION: main
10-26 13:57:50.132: E/AndroidRuntime(8663): java.lang.RuntimeException: Unable to pause activity {.views.MainActivity}: java.lang.IllegalStateException: Failure saving state: active LoginFragment{4053d5a0} has cleared index: -1
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2365)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2322)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:2302)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.access$1700(ActivityThread.java:117)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:949)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.os.Handler.dispatchMessage(Handler.java:99)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.os.Looper.loop(Looper.java:130)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.main(ActivityThread.java:3694)
10-26 13:57:50.132: E/AndroidRuntime(8663): at java.lang.reflect.Method.invokeNative(Native Method)
10-26 13:57:50.132: E/AndroidRuntime(8663): at java.lang.reflect.Method.invoke(Method.java:507)
10-26 13:57:50.132: E/AndroidRuntime(8663): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-26 13:57:50.132: E/AndroidRuntime(8663): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-26 13:57:50.132: E/AndroidRuntime(8663): at dalvik.system.NativeStart.main(Native Method)
10-26 13:57:50.132: E/AndroidRuntime(8663): Caused by: java.lang.IllegalStateException: Failure saving state: active LoginFragment{4053d5a0} has cleared index: -1
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.support.v4.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1695)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.support.v4.app.FragmentActivity.onSaveInstanceState(FragmentActivity.java:499)
10-26 13:57:50.132: E/AndroidRuntime(8663): at views.MainActivity.onSaveInstanceState(MainActivity.java:62)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.Activity.performSaveInstanceState(Activity.java:1042)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1181)
10-26 13:57:50.132: E/AndroidRuntime(8663): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2347)
10-26 13:57:50.132: E/AndroidRuntime(8663): ... 12 more
我不知道这个错误来自什么以及这个错误的一般原因是什么。
编辑：
对不起，我会提供更多信息。基本上，我有一个 FragmentActivity （这是我的Tabhost），每个选项卡都是一个片段，我可以从中导航到另一个片段。
具体场景如下：
- 应用程序打开，显示带有 Fragment 0 (
LoginFragment) 的 Tab 0。 - 用户登录，LoginFragment 被 ProfileFragment 替换。
- 从 中
ProfileFragment，用户可以注销，并且这样做了，这将 Profilefragment 再次替换为 Loginfragment。 - 用户从 TabHost 导航到不同的选项卡。
- 用户导航回原始选项卡。
- 然后用户锁定屏幕/使用主页按钮，使应用程序因给定错误而崩溃。
我只在这种特定情况下得到错误。
错误源自 中的 TabManager 类TabHost FragmentActivity，代码如下（主要来自 Android FragmentTabs 示例，稍作调整）：
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;
}
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);
}
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);
}
}
int backEntryCount = mActivity.getSupportFragmentManager().getBackStackEntryCount();
if (backEntryCount > 1) {
mActivity.getSupportFragmentManager().popBackStack(null, 0);
}
//If there's a current BackTrace, remove it and instantiate the original fragment of the selected tab.
FragmentManager fm = mActivity.getSupportFragmentManager();
if (fm.getBackStackEntryCount() >= 1) {
fm.popBackStack();
newTab.fragment.getFragmentManager().beginTransaction().add(mLastTab.fragment.getId(), newTab.fragment = Fragment.instantiate(mActivity,
newTab.clss.getName(), newTab.args));
}
if (mActivity.getSupportFragmentManager().findFragmentByTag("userprofile") != null) {
Fragment fragment = mActivity.getSupportFragmentManager().findFragmentByTag("userprofile");
ft.detach(fragment);
}
if (newTab.fragment.getClass().getName().contains("Login") && Preferences.getUser(mActivity).getApikey() != null) {
ft.replace(mLastTab.fragment.getId(), new ProfileFragment(), "userprofile");
ft.detach(newTab.fragment);
}
if (mActivity.getSupportFragmentManager().findFragmentByTag("Profile") != null) {
if (mActivity.getSupportFragmentManager().findFragmentByTag("Profile").isDetached() == true) {
System.out.println(true);
Fragment fragment = mActivity.getSupportFragmentManager().findFragmentByTag("Profile");
mActivity.getSupportFragmentManager().beginTransaction().replace(fragment.getId(), new LoginFragment(), "Profile").commit();
}
}
mLastTab = newTab;
ft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
}
}
}