在Android中隐藏显示片段

Question

i have a fragment and want hide and show with a button. I Use this code :

 public class Tablo extends FragmentActivity{
Fragment fg ;
Button click ;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tablo);
    fg = getFragmentManager().findFragmentById(R.id.emojicons);
    click = (Button) findViewbyId(R.id.Button1);
    click.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            FragmentManager fm = getFragmentManager();
            fm.beginTransaction()
                    .setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
                    .show(fg)
                    .commit();
        }
    });

Log Error :

 java.lang.NullPointerException: Attempt to write to field 'int android.app.Fragment.mNextAnim' on a null object reference
        at android.app.BackStackRecord.run(BackStackRecord.java:809)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
        at android.app.FragmentManagerImpl$1.run(FragmentManager.java:452)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:145)
        at android.app.ActivityThread.main(ActivityThread.java:6145)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

Fragment in Xml :

<fragment
    android:id="@+id/emojicons"
    android:layout_width="match_parent"
    android:layout_height="220dp"
    class="ir.m.sh.textsticker.PlusOneFragment"/>

My Fragment :

Android Studio PLusOneFragment

whats wrong ?

i want show and hide this fragment and tested all way but ...

Answer 1

I guess that your fragment object is null. Try like this:

PLusOneFragment fg ;
Button click ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tablo);
if(savedInstanceState == null)
    fg = new PLusOneFragment();
else
    fg = getFragmentManager().findFragmentById(R.id.emojicons);
click = (Button) findViewbyId(R.id.Button1);
click.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        FragmentManager fm = getFragmentManager();
        fm.beginTransaction()
                .setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
                .show(fg)
                .commit();
    }
});

Or if you want, instead of a PLusOneFragment object you can use a Fragment object and then when initialize it you can initialize it like that: Fragment fg; fg = new PLusOneFragment(); (where savedInstanceState is null);