最近做一個功能，當第二次進入一個介面的時候出現一個奇怪的bug,如下面詳細的log資訊：

10-01 13:36:23.549: E/AndroidRuntime(14188): Process: com.android.settings, PID: 14188
10-01 13:36:23.549: E/AndroidRuntime(14188): android.view.InflateException: Binary XML file line #43: Error inflating class fragment
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:713)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.view.LayoutInflater.rInflate(LayoutInflater.java:755)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at com.android.settings.accessibility.ToggleCaptioningPreferenceFragment.onCreateView(ToggleCaptioningPreferenceFragment.java:69)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.Fragment.performCreateView(Fragment.java:1700)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.BackStackRecord.run(BackStackRecord.java:698)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.os.Handler.handleCallback(Handler.java:808)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.os.Handler.dispatchMessage(Handler.java:103)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.os.Looper.loop(Looper.java:193)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.ActivityThread.main(ActivityThread.java:5333)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at java.lang.reflect.Method.invokeNative(Native Method)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at java.lang.reflect.Method.invoke(Method.java:515)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at dalvik.system.NativeStart.main(Native Method)
10-01 13:36:23.549: E/AndroidRuntime(14188): Caused by: java.lang.IllegalArgumentException: Binary XML file line #43: Duplicate id 0x7f0b0034, tag null, or parent id 0xffffffff with another fragment for com.android.settings.accessibility.CaptionPropertiesFragment
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.app.Activity.onCreateView(Activity.java:4912)
10-01 13:36:23.549: E/AndroidRuntime(14188): 	at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:689)
 

如上的log資訊可以知道：載入了一個（Duplicate）重複的Fragment（CaptionPropertiesFragment）。問題是程式碼應該是沒有問題的！具體看看我係的程式碼：

public class ToggleCaptioningPreferenceFragment extends Fragment {
    private static final float DEFAULT_FONT_SIZE = 48f;

    private CaptionPropertiesFragment mPropsFragment;
    private SubtitleView mPreviewText;
    private CaptioningManager mCaptioningManager;


	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mCaptioningManager = (CaptioningManager) getActivity()
                .getSystemService(Context.CAPTIONING_SERVICE);
    }

    @Override
    public View onCreateView(
            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
	

        final View rootView = inflater.inflate(R.layout.captioning_preview, container, false);

        // We have to do this now because PreferenceFrameLayout looks at it
        // only when the view is added.
        if (container instanceof PreferenceFrameLayout) {
            ((PreferenceFrameLayout.LayoutParams) rootView.getLayoutParams()).removeBorders = true;
        }


        return rootView;
    }
 

從報錯資訊可以知道出錯的程式碼：final View rootView = inflater.inflate(R.layout.captioning_preview, container, false);

那麼報錯資訊說是載入了重複的Fragment（CaptionPropertiesFragment）。實際上這個重複的Fragment在這個layout檔案裡面佈局的：R.layout.captioning_preview。

很顯然，就是第一次進入這個介面，再退出的時候，這個用過的Fragment（CaptionPropertiesFragment）沒有remove掉！從而出現了兩個問題：

（1）為什麼會出現這個Fragment（CaptionPropertiesFragment）沒有remove,

（2）怎麼解決這個問題！

        在activity中不同的frament之間專案替換的時候，FragmentManager只會remove和add這些frament，然而這些frament裡面自己載入的frament（這裡就是我們的CaptionPropertiesFragment）是沒有被remove. 很顯然這是一個缺陷！因為後一個frament（CaptionPropertiesFragment）很明顯是依賴與他的父frament的，應該同時遞迴的remove.

        那麼如何解決這個問題呢！很顯然就是在不用這個frament（ToggleCaptioningPreferenceFragment）的時候把他裡面載入的frament給remove掉！這個操作在ToggleCaptioningPreferenceFragment的onDestroyView()裡面就可以解決問題了！如下程式碼：

	@Override
	public void onDestroyView() {
		super.onDestroyView();

	 	if(mPropsFragment != null){
			FragmentManager f = getFragmentManager();
			if(f != null && !f.isDestroyed()){
				final FragmentTransaction ft = f.beginTransaction();
				if(ft != null){
					ft.remove(mPropsFragment).commit();
				}
			}
	 	}
	}

      這裡要注意f.isDestroyed()這樣來判斷是否這個FragmentManager處於Destroyed，如果不加這個判斷的話，橫豎屏切換時候會出錯！

     注意：對於這個問題，網上有各種無效的解決辦法。