Je viens d'apprendre studio android, chaque fois que j'essaie d'utiliser startactivity (intention), de mon activité "signup_activ", l'application se bloque

Question

l'application se bloque quand je clique sur le bouton sur signup_activ pour démarrer userdetail_activ, si je swithc à d'autres activité istead, l'application fonctionne bien

Ceci est mon fichier manifeste.

<application 
    android:allowBackup="true" 
    android:icon="@mipmap/ic_launcher" 
    android:label="@string/app_name" 
    android:roundIcon="@mipmap/ic_launcher_round" 
    android:supportsRtl="true" 
    android:theme="@style/AppTheme"> 
    <activity android:name=".MainActivity"> 
     <intent-filter> 
      <action android:name="android.intent.action.MAIN" /> 

      <category android:name="android.intent.category.LAUNCHER" /> 
     </intent-filter> 
    </activity> 
    <activity 
     android:name=".login_activ" 
     android:parentActivityName=".MainActivity" /> 
    <activity 
     android:name=".signup_activ" 
     android:parentActivityName=".MainActivity" /> 
    <activity 
     android:name=".userdetail_activ" 
     android:parentActivityName=".signup_activ" > 

    </activity> 
    <activity android:name=".userdetail_activ2" /> 
    <activity android:name=".infopage_activ"></activity> 
</application> 

</manifest> 

après le blocage de l'application.

AndroidRuntime: FATAL EXCEPTION: main 
                         Process: com.example.ozairmansuri.myapplication, PID: 1986 
                         java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.ozairmansuri.myapplication/com.example.ozairmansuri.myapplication.userdetail_activ}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference 
                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2567) 
                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                          at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                          at android.os.Handler.dispatchMessage(Handler.java:102) 
                          at android.os.Looper.loop(Looper.java:154) 
                          at android.app.ActivityThread.main(ActivityThread.java:6119) 
                          at java.lang.reflect.Method.invoke(Native Method) 
                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
                         Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference 
                          at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:118) 
                          at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:152) 
                          at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:29) 
                          at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:53) 
                          at android.support.v7.app.AppCompatDelegateImplV23.<init>(AppCompatDelegateImplV23.java:31) 
                          at android.support.v7.app.AppCompatDelegateImplN.<init>(AppCompatDelegateImplN.java:31) 
                          at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:200) 
                          at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:184) 
                          at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:518) 
                          at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:189) 
                          at com.example.ozairmansuri.myapplication.userdetail_activ.<init>(userdetail_activ.java:22) 
                          at java.lang.Class.newInstance(Native Method) 
                          at android.app.Instrumentation.newActivity(Instrumentation.java:1078) 
                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2557) 
                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
                          at android.app.ActivityThread.-wrap12(ActivityThread.java)  
                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
                          at android.os.Handler.dispatchMessage(Handler.java:102)  
                          at android.os.Looper.loop(Looper.java:154)  
                          at android.app.ActivityThread.main(ActivityThread.java:6119)  
                          at java.lang.reflect.Method.invoke(Native Method)  
                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  

signup_activ

import android.content.Intent; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.Toast; 

import java.util.ArrayList; 
import java.util.List; 
import java.util.regex.Pattern; 

public class signup_activ extends AppCompatActivity { 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_signup_activ); 
    } 

    public void UserDet_Switch() { 
     final Intent intent = new Intent(signup_activ.this, userdetail_activ.class); 
     startActivity(intent); 
     return; 
    } 

    public void Signup(View view) { 
     EditText editText = (EditText) findViewById(R.id.editTextUserName); 
     EditText editText2 = (EditText) findViewById(R.id.editTextPassword); 
     EditText editText3 = (EditText) findViewById(R.id.editTextConfirmPassword); 
     String A = editText.getText().toString(); 
     String B = editText2.getText().toString(); 
     String C = editText3.getText().toString(); 

     List<String> errorList = new ArrayList<String>(); 

     while (!isValid_pass(B, C, errorList)) {        //checking whether password is valid 

      for (String error : errorList) { 
       Toast.makeText(getApplicationContext(), error, 
         Toast.LENGTH_SHORT).show(); 
       return; 
      } 
     } 
     List<String> errorList2 = new ArrayList<String>(); 

     while (!isValid_usern(A,errorList2)){         //checking whethe user name is valid 
      for (String error : errorList2) { 
       Toast.makeText(getApplicationContext(), error, 
         Toast.LENGTH_SHORT).show(); 
       return; 
      } 
     } 
     SQLhelper dbh =new SQLhelper(this) ; 
     if(dbh.checkUser(A,B)== true){ 
      Toast.makeText(getApplicationContext(),"user alredy exists", 
        Toast.LENGTH_SHORT).show(); 
      return; 
     } 
     dbh.addUser(A,B);              //adding the user to database table 1 
     Toast.makeText(getApplicationContext(), "account created", 
       Toast.LENGTH_SHORT).show(); 
     //// TODO: 28-09-2017 intent switch activity (userdetil activity) 
     UserDet_Switch(); 
     return; 

    } 

    //function to check userncme 

    public static boolean isValid_usern(String usern,List<String> errorList){ 


     Pattern lowerCasePatten = Pattern.compile("[a-z ]"); 
     Pattern digitCasePatten = Pattern.compile("[0-9 ]"); 
     errorList.clear(); 

     boolean flag=true; 
     if (usern.length() < 8) { 
      errorList.add("user name lenght must have alleast 8 character !!"); 
      flag=false; 
     } 


     if (!lowerCasePatten.matcher(usern).find()) { 
      errorList.add("user name must have atleast one lowercase character !!"); 
      flag=false; 
     } 
     if (!digitCasePatten.matcher(usern).find()) { 
      errorList.add("user name must have atleast one digit character !!"); 
      flag=false; 
     } 
     return flag; 
    } 

    //function to check password 

    public static boolean isValid_pass(String passwordhere, String confirmhere, List<String> errorList) { 



     Pattern lowerCasePatten = Pattern.compile("[a-z ]"); 
     Pattern digitCasePatten = Pattern.compile("[0-9 ]"); 
     errorList.clear(); 

     boolean flag=true; 

     if (!passwordhere.equals(confirmhere)) { 
      errorList.add("password and confirm password does not match"); 
      flag=false; 
     } 
     if (passwordhere.length() < 8) { 
      errorList.add("Password lenght must have alleast 8 character !!"); 
      flag=false; 
     } 


     if (!lowerCasePatten.matcher(passwordhere).find()) { 
      errorList.add("Password must have atleast one lowercase character !!"); 
      flag=false; 
     } 
     if (!digitCasePatten.matcher(passwordhere).find()) { 
      errorList.add("Password must have atleast one digit character !!"); 
      flag=false; 
     } 

     return flag; 

    } 

    } 

userdetail_activ

import android.content.ContentValues; 
import android.content.Intent; 
import android.provider.MediaStore; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.RadioButton; 
import android.widget.RadioGroup; 
import android.widget.Toast; 

public class userdetail_activ extends AppCompatActivity { 
    public static final String EXTRA_HEIGHT = "height"; 
    public static final String EXTRA_WEIGHT = "weight"; 
    public static final String EXTRA_GENDER = "gender"; 
    RadioButton rb; 
    RadioGroup rg ; 
    Boolean gend =null; 
    int A,B; 
    EditText editText = (EditText) findViewById(R.id.editText6); 
    EditText editText2 = (EditText) findViewById(R.id.editText9); 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_userdetail_activ); 
     rg = (RadioGroup) findViewById(R.id.radio_group); 
    } 
    public void rb_click(View view){          //radio button function 
     int radioButtonid = rg.getCheckedRadioButtonId(); 
     rb = (RadioButton) findViewById(radioButtonid); 
    if(radioButtonid == (R.id.radioButton2)) gend=true;     //male is true 
     else gend = false;             //female is false 
     return; 
    } 

    public void continue_userdetail(View view){ 
     A = Integer.parseInt(editText.getText().toString()); 
     B = Integer.parseInt(editText2.getText().toString()); 
     if(gend == null) 
     { 
      Toast.makeText(getApplicationContext(), "please select gender", 
        Toast.LENGTH_SHORT).show(); 
      return; 
     } 

     Intent intent = new Intent(this, userdetail_activ2.class); 
     intent.putExtra(EXTRA_HEIGHT,A); 
     intent.putExtra(EXTRA_WEIGHT,B); 
     intent.putExtra(EXTRA_GENDER,gend); 
     startActivity(intent); 
     return; 
    } 
} 

Answer 1

EditText editText = (EditText) findViewById(R.id.editText6); 
EditText editText2 = (EditText) findViewById(R.id.editText9); 

jamais appeler des méthodes que vous héritez de Activity qu'après super.onCreate() a été appelé, à moins documentée autrement.

N'appelez jamais findViewById() jusqu'à ce que les widgets existent, par exemple en cours de création via un appel à setContentView().

Déplacez l'initialisation de ces deux champs jusqu'à ce que setContentView() soit appelée en onCreate().