I have two frament login password and verification code, each contains the following two controls

 @ Override 
Protected void onStart () {
Super. OnStart (); 
/login/password. 
Phone_p=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_phone_p); 
The password/login/password 
PSW=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_psw); 
//login authentication code phone number 
Phone_v=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_phone_v); 
//login verification code verification code 
Verification=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_verification); 
} 

Is the default password

 
Protected void onCreate (Bundle savedInstanceState) {
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 
//the default password login page (fragments: 0) 
SelectFragment (0); 
} 
//select display fragments 
Private void selectFragment (int fragmentId) {
//get the Fragment manager 
FragmentManager manager=getFragmentManager (); 
//open a transaction 
FragmentTransaction transaction=manager. BeginTransaction (); 
//hide first Fragment 
HideFragment (transaction); 

If (fragmentId==0) {/login/password 
FragmentNumber=fragmentId; 
If (pwdFragment==null) {
PwdFragment=new PwdActivity (); 
Transaction. The add (R.i d.f ragment_content pwdFragment); 
} else {
Transaction. The show (pwdFragment); 
} 
} else if (fragmentId==1) {//login authentication code 
FragmentNumber=fragmentId; 
If (verificationFragment==null) {
VerificationFragment=new VerificationActivity (); 
Transaction. The add (R.i d.f ragment_content verificationFragment); 
} else {
Transaction. The show (verificationFragment); 
} 
} 

//to commit the transaction 
transaction.commit(); 
} 

When I use the verification code fragments after switch login fragments can lead to app flash back, the problem in the following two controls is empty, how to solve?

//login authentication code mobile number 
Phone_v=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_phone_v); 
//login verification code verification code 
Verification=getFragmentManager (.) findFragmentById (R.i d.f ragment_content). The getView (). The findViewById (R.i d.i nput_verification);