Problems with Fragmentmanager in Android

Fragment is an important part of a flexible UI. Recently learned the use of fragment, encountered a problem. The main program layout is very simple:

<?xml version= "1.0" encoding= "Utf-8"? ><android.support.v4.widget.slidingpanelayout    xmlns:android= " Http://schemas.android.com/apk/res/android "    android:id=" @+id/slidingpanellayout "    android:layout_width= "Match_parent"    android:layout_height= "match_parent" >    <fragment        android:id= "@+id/ Bookmarkfragment "        android:name=" com.hnb.zzk.slidingpanellayouttest.BookMarkerFragment "        android:layout_ Width= "100DP"        android:layout_height= "match_parent"        android:layout_gravity= "left"/>    < Fragment        android:id= "@+id/browserfragment"        android:name= " Com.hnb.zzk.slidingpanellayouttest.BrowserFragment "        android:layout_width=" Match_parent "        android: layout_height= "Match_parent"        android:layout_gravity= "right"        android:layout_weight= "1"/></ Android.support.v4.widget.slidingpanelayout>

Is that two fragment form the main layout, and then get the fragment in the Java code:

Slidingpanelayout SPL = (slidingpanelayout) This.findviewbyid (r.id.slidingpanellayout); Spl.setpanelslidelistener ( New Slidingpanelayout.panelslidelistener () {    @Override public    void Onpanelslide (View panel, float slideoffset {    }    @Override public    void onpanelopened (View panel) {        MainActivity.this.getFragmentManager (). Findfragmentbyid (r.id.bookmarkfragment). Sethasoptionsmenu (True);    }    @Override public    void onpanelclosed (View panel) {        MainActivity.this.getFragmentManager (). Findfragmentbyid ( r.id.bookmarkfragment). Sethasoptionsmenu (False);    }});

Initially it seemed like everything went well and the code was a mess of streamlining. So run up to see, in the simulator but directly collapse, and quickly add the exception capture code, get the following results:

Java.lang.NullPointerExceptionat com.hnb.zzk.slidingpanellayouttest.mainactivity$2.onpanelopened ( mainactivity.java:44) at android.support.v4.widget.SlidingPaneLayout.dispatchOnPanelOpened ( slidingpanelayout.java:343) at android.support.v4.widget.slidingpanelayout$ Draghelpercallback.onviewdragstatechanged (slidingpanelayout.java:1318) at Android.support.v4.widget.ViewDragHelper.setDragState (viewdraghelper.java:874) at Android.support.v4.widget.ViewDragHelper.forceSettleCapturedViewAt (viewdraghelper.java:592) at Android.support.v4.widget.ViewDragHelper.settleCapturedViewAt (viewdraghelper.java:569) at Android.support.v4.widget.slidingpanelayout$draghelpercallback.onviewreleased (SlidingPaneLayout.java:1354) at Android.support.v4.widget.ViewDragHelper.dispatchViewReleased (viewdraghelper.java:767) at Android.support.v4.widget.ViewDragHelper.releaseViewForPointerUp (viewdraghelper.java:1395) at Android.support.v4.widget.ViewDragHelper.processTouchEvent (viewdraghelper.java:1213) at Android.support.v4.widgeT.slidingpanelayout.ontouchevent (slidingpanelayout.java:826) 

A null pointer exception occurred in the Onpanelopend () method. Possible null pointer exceptions are Getfragmentmanager () and Findfragmentbyid () two calls. Findfragmentbyid () should be less likely to have a null pointer exception, and two fragment in the layout file are obvious. Then it can only be said that Getfragmentmanager () This call appears with a pointer. In fragment's development documentation, it is clear that fragment management is implemented through Fragmentmanager, so where does the problem arise? Search on the internet finally found the crux of the problem. We are referencing the fragment component in the V4 Compatibility Pack, and Getfragmentmanager () is fragment for v11+, so replace Getfragmentmanager () with Getsupportfragmentmanager () just fine.

Problems with Fragmentmanager in Android