Android - Impossible de changer le texte dans TextView

Question

Je viens de commencer à apprendre Android et j'ai un problème. Avec le nouveau Android Studio j'ai deux fichiers XML pour chaque activité, afin de ne pas obtenir NullPointerException J'ai dû changer un peu ma findViewById. Mais maintenant je suis incapable de changer le texte en TextView.

Code:

public class MainActivity extends AppCompatActivity { 


    LinearLayout layoutMain; 
    TextView tvText; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     layoutMain = (LinearLayout) View.inflate(this, R.layout.content_main, null); 
     tvText = (TextView) layoutMain.findViewById(R.id.tvText); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.menu_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     int id = item.getItemId(); 

     switch (id) { 
      case R.id.action_settings1: 
        tvText.setText("one"); 
       Log.d("USER","one"); 
       break; 
      case R.id.action_settings2: 
       tvText.setText("two"); 
       Log.d("USER", "two"); 
       break; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

} 

fichiers XML:

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    app:layout_behavior="@string/appbar_scrolling_view_behavior" 
    tools:context="com.example.myapp6.MainActivity" 
    tools:showIn="@layout/activity_main"> 


    <TextView 
     android:id="@+id/tvText" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="Hello World!" /> 
</LinearLayout> 

<android.support.design.widget.AppBarLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:theme="@style/AppTheme.AppBarOverlay"> 

    <android.support.v7.widget.Toolbar 
     android:id="@+id/toolbar" 
     android:layout_width="match_parent" 
     android:layout_height="?attr/actionBarSize" 
     android:background="?attr/colorPrimary" 
     app:popupTheme="@style/AppTheme.PopupOverlay" /> 

</android.support.design.widget.AppBarLayout> 

<include layout="@layout/content_main" /> 

Answer 1

Changer

tvText = (TextView) layoutMain.findViewById(R.id.tvText); 

à

tvText = (TextView) findViewById(R.id.tvText); 

Vous avez été trouvé une référence incorrecte au TextView.

Answer 2

public class MainActivity extends AppCompatActivity { 

View includedView; 
TextView tvText; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 

    includedView = (View) findViewById(R.id.includedView); 
    tvText = (TextView) includedView.findViewById(R.id.tvText); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.menu_main, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    int id = item.getItemId(); 

    switch (id) { 
     case R.id.action_settings1: 
       tvText.setText("one"); 
      Log.d("USER","one"); 
      break; 
     case R.id.action_settings2: 
      tvText.setText("two"); 
      Log.d("USER", "two"); 
      break; 
    } 
    return super.onOptionsItemSelected(item); 
} 

} 

aussi peu de changements de bits dans vos fichiers xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:app="http://schemas.android.com/apk/res-auto" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
app:layout_behavior="@string/appbar_scrolling_view_behavior" 
tools:context="com.example.myapp6.MainActivity" 
tools:showIn="@layout/activity_main"> 


<TextView 
    android:id="@+id/tvText" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Hello World!" /> 
</LinearLayout> 

et deuxième xml

<android.support.design.widget.AppBarLayout 
android:layout_width="match_parent" 
android:layout_height="wrap_content" 
android:theme="@style/AppTheme.AppBarOverlay"> 

<android.support.v7.widget.Toolbar 
    android:id="@+id/toolbar" 
    android:layout_width="match_parent" 
    android:layout_height="?attr/actionBarSize" 
    android:background="?attr/colorPrimary" 
    app:popupTheme="@style/AppTheme.PopupOverlay" /> 

</android.support.design.widget.AppBarLayout> 

<include layout="@layout/content_main" 
android:id="@+id/includedView"/> 

Answer 3

Copiez et collez votre mise en page content_main à l'intérieur activity_main xml et supprimez le fichier content_main xml.

Ensuite, changez le code dans onCreate() comme:

@Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     layoutMain = (LinearLayout) findViewById(R.id.content_main); 
     //content_main should be the id of the layout you copied! 

     tvText = (TextView) findViewById(R.id.tvText); 
    }