Android Application keeps crashing

Question

I want to make an application which on login shows a "home" activity which has a navigation bar. I used android studios navigation drawer template and edited it to switch between fragments, but now the application is crashing on login. Any help on what am I doing wrong is appreciated.

P.S. I am an amateur so I apologize for any stupid questions asked.

package zade.example.com.zade;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;


public class Student_Home extends ActionBarActivity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

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

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {

        Fragment objfragment = null;

        switch (position) {
            case 1:
                objfragment = new MyFragment1();
                break;
            case 2:
                objfragment = new MyFragment2();
                break;
            case 3:
                objfragment = new MyFragment3();
                break;
        }
        // update the main content by replacing fragments
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction()
                .replace(R.id.container, objfragment)
                .commit();
    }

    public void onSectionAttached(int number) {
        switch (number) {
            case 1:
                mTitle = getString(R.string.title_section1);
                break;
            case 2:
                mTitle = getString(R.string.title_section2);
                break;
            case 3:
                mTitle = getString(R.string.title_section3);
                break;
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.student__home, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @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);
    }

}

The logcat is :

 E/AndroidRuntime﹕ FATAL EXCEPTION: main
        Process: zade.example.com.zade, PID: 2052
        java.lang.RuntimeException: Unable to start activity ComponentInfo{zade.example.com.zade/zade.example.com.zade.Student_Home}: android.view.InflateException: Binary XML file line #19: Error inflating class fragment
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
                at android.app.ActivityThread.access$800(ActivityThread.java:144)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5221)
                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:899)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
         Caused by: android.view.InflateException: Binary XML file line #19: Error inflating class fragment
                at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
                at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
                at android.support.v7.app.ActionBarActivityDelegateBase.setContentView(ActionBarActivityDelegateBase.java:228)
                at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:102)
                at zade.example.com.zade.Student_Home.onCreate(Student_Home.java:29)
                at android.app.Activity.performCreate(Activity.java:5933)
                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
                at android.app.ActivityThread.access$800(ActivityThread.java:144)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5221)
                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:899)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
         Caused by: java.lang.NullPointerException: Attempt to write to field 'android.support.v4.app.FragmentManagerImpl android.support.v4.app.Fragment.mFragmentManager' on a null object reference
                at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:416)
                at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:451)
                at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:443)
                at zade.example.com.zade.Student_Home.onNavigationDrawerItemSelected(Student_Home.java:60)
                at zade.example.com.zade.NavigationDrawerFragment.selectItem(NavigationDrawerFragment.java:200)
                at zade.example.com.zade.NavigationDrawerFragment.onCreate(NavigationDrawerFragment.java:79)
                at android.support.v4.app.Fragment.performCreate(Fragment.java:1763)
                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:913)
                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
                at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1206)
                at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2159)
                at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:297)
                at android.support.v7.app.ActionBarActivity.onCreateView(ActionBarActivity.java:547)
                at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
                at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
                at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
                at android.support.v7.app.ActionBarActivityDelegateBase.setContentView(ActionBarActivityDelegateBase.java:228)
                at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:102)
                at zade.example.com.zade.Student_Home.onCreate(Student_Home.java:29)
                at android.app.Activity.performCreate(Activity.java:5933)
                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
                at android.app.ActivityThread.access$800(ActivityThread.java:144)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5221)
                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:899)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

I've quickly reviewed your code - I couldn't see the exact line which gives you this problem but acording to your Logcat it is obvious you have forgotten to initialize something or either you have initialized something very lately and tried to use it before the initialization : 90% of the times you get the "ComponentInfo" error because of this.

I'll try to have a close look later but from this tip you should be able to find and fix it yourself.

Best, Mack.