Wie kann ich eine fragmentTransaction in anderen Klassen tun?

Question

Ich möchte eine Klasse erstellen, deren Funktion nur eine FragmentTransaction ist, aber ich habe einen Fehler. Meine Klasse ist die nächste:

package net.elinformaticoenganchado.sergio.crossfighters.common; 

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.app.FragmentTransaction; 

import net.elinformaticoenganchado.sergio.crossfighters.R; 
import net.elinformaticoenganchado.sergio.crossfighters.statics.Main; 

/** 
* @author Sergio Herrero Cruz <sergioherre96@gmail.com> 
* @package net.elinformaticoenganchado.sergio.crossfighters.common 
*/ 
public class FragmentsGoTo extends FragmentActivity{ 


    public void goToMainFragment() { 
     Fragment fragment = new Main(); 
     FragmentTransaction ftConfig = getSupportFragmentManager().beginTransaction(); 
     ftConfig.replace(R.id.main_frame, fragment); 
     ftConfig.commit(); 
    } 
} 

Und ich rufe hier auf diese Funktion:

package net.elinformaticoenganchado.sergio.crossfighters.configuration; 

import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.EditText; 
import net.elinformaticoenganchado.sergio.crossfighters.R; 
import net.elinformaticoenganchado.sergio.crossfighters.common.FragmentsGoTo; 
import net.elinformaticoenganchado.sergio.crossfighters.entity.Configuration; 

/** 
* @author Sergio Herrero Cruz <sergioherre96@gmail.com> 
*/ 
public class ConfigurationEdit extends Fragment implements View.OnClickListener{ 

    EditText name; 

    /** 
    * @param inflater   The LayoutInflater object that can be used to inflate 
    *       any views in the fragment, 
    * @param container   If non-null, this is the parent view that the fragment's 
    *       UI should be attached to. The fragment should not add the view itself, 
    *       but this can be used to generate the LayoutParams of the view. 
    * @param savedInstanceState If non-null, this fragment is being re-constructed 
    *       from a previous saved state as given here. 
    * @return Return the View for the fragment's UI, or null. 
    */ 
    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.configuration_edit, container, false); 

     name = (EditText) view.findViewById(R.id.configuration_edit_name); 
     Button save = (Button) view.findViewById(R.id.configuration_edit_button); 

     save.setOnClickListener(this); 

     return view; 
    } 

    /** 
    * Called when a view has been clicked. 
    * 
    * @param v The view that was clicked. 
    */ 
    @Override 
    public void onClick(View v) { 
     if (v.getId() == R.id.configuration_edit_button) { 
      Configuration config = new Configuration(name.getText().toString()); 
      config.save(); 
      FragmentsGoTo fragmentsGoTo = new FragmentsGoTo(); 
      fragmentsGoTo.goToMainFragment(); 
     } 
    } 

} 

Sie sind einfach Klasse. Aber ich habe einen Fehler:

Process: net.elinformaticoenganchado.sergio.crossfighters, PID: 5116 java.lang.RuntimeException: Unable to start activity ComponentInfo{net.elinformaticoenganchado.sergio.crossfighters/net.elinformaticoenganchado.sergio.crossfighters.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.v4.app.FragmentManager android.support.v4.app.FragmentActivity.getSupportFragmentManager()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.v4.app.FragmentManager android.support.v4.app.FragmentActivity.getSupportFragmentManager()' on a null object reference at net.elinformaticoenganchado.sergio.crossfighters.common.FragmentsGoTo.goToMainFragment(FragmentsGoTo.java:19) at net.elinformaticoenganchado.sergio.crossfighters.MainActivity.onCreate(MainActivity.java:42) at android.app.Activity.performCreate(Activity.java:6237) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)  at android.app.ActivityThread.-wrap11(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:148)  at android.app.ActivityThread.main(ActivityThread.java:5417)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Also wie kann ich das in Java ohne Fehler.

Vielen Dank.

Edit: hinzufügen mainActivity Klasse:

package net.elinformaticoenganchado.sergio.crossfighters; 

import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentTransaction; 
import android.view.View; 
import android.support.design.widget.NavigationView; 
import android.support.v4.view.GravityCompat; 
import android.support.v4.widget.DrawerLayout; 
import android.support.v7.app.ActionBarDrawerToggle; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.Menu; 
import android.view.MenuItem; 
import net.elinformaticoenganchado.sergio.crossfighters.common.FragmentsGoTo; 
import net.elinformaticoenganchado.sergio.crossfighters.configuration.ConfigurationEdit; 
import net.elinformaticoenganchado.sergio.crossfighters.entity.Configuration; 

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     setContentView(R.layout.activity_main); 

     FragmentsGoTo fragmentsGoTo = new FragmentsGoTo(); 
     //@Todo change for start 
     //Configuration.deleteAll(Configuration.class); 

     if (Configuration.count(Configuration.class) == 0) { 
      Fragment fragment = new ConfigurationEdit(); 
      FragmentTransaction ftConfig = getSupportFragmentManager().beginTransaction(); 
      ftConfig.replace(R.id.main_frame, fragment); 
      ftConfig.commit(); 
     } else { 
      fragmentsGoTo.goToMainFragment(); 
     } 

     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
       this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
     drawer.addDrawerListener(toggle); 
     toggle.syncState(); 

     NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
     navigationView.setNavigationItemSelectedListener(this); 
    } 

    @Override 
    public void onBackPressed() { 
     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     if (drawer.isDrawerOpen(GravityCompat.START)) { 
      drawer.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

    @SuppressWarnings("StatementWithEmptyBody") 
    @Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     // Handle navigation view item clicks here. 
     int id = item.getItemId(); 

     if (id == R.id.nav_camera) { 
      // Handle the camera action 
     } else if (id == R.id.nav_gallery) { 

     } else if (id == R.id.nav_slideshow) { 

     } else if (id == R.id.nav_manage) { 

     } else if (id == R.id.nav_share) { 

     } else if (id == R.id.nav_send) { 

     } 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 
} 

Answer 1

Da mein Kommentar fix geholfen:

This is not the way to instantiate the activity (calling new). Google a bit, use intents. You need an activity which HOLDS the fragments, and then to swap the fragments in it.