Android Developing App crashes

Question

Hi guys, I started to learn developing app for android today. My guide is New Boston: https://buckysroom.org/videos.php?cat=6&video=16731 I passed every tutorial until the 10th because: I did every step, but the app crashes. Here is the XML code:

    <Button
        android:id="@+id/bAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvDisplay"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:text="Add here" />

    <TextView
        android:id="@+id/tvDisplay"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="18dp"
        android:text="The total is: " />

</RelativeLayout>

And here is the JAVA code:

package com.example.firstpro;



public class MainActivity extends ActionBarActivity {

int c = 0;
Button add, sub;
TextView display;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    add = (Button) findViewById(R.id.bAdd);
    display = (TextView) findViewById(R.id.tvDisplay);
    add.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            c+=1;
            display.setText("You're total is: " + c);
            setContentView(R.layout.activity_main);
        }
    });

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
          .add(R.id.container, new PlaceholderFragment()).commit();
    }
}

@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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        return rootView;
    }
}

}

I really don't know what's the problem here. There is no error even warning. I hope for answers. Thanks.

Smells like http://stackoverflow.com/questions/23653778/nullpointerexception-accessing-views-in-oncreate — laalto, Jun 26 '14 at 20:29
@iYonatan That's not the message he's talking about. He wants to know what the Logcat says. As to the issue, this is the big problem with using tutorial videos for learning new(ish) technologies. Wait 5 minutes and the video is out of date. This is the case here. The tutorial does not account for Android's recent template changes that put Fragments into everything. I suspect your issue has to do with the Fragment, but without seeing the Logcat, I cannot answer any more specifically. — Stephen S, Jun 26 '14 at 20:56

Zoran · Accepted Answer · 2014-06-26T21:27:47.413

0

Your button and textview are in fragment layout, not in activity layout so you have to move your code to onCreateView:

public class MainActivity extends ActionBarActivity {

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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
          .add(R.id.container, new PlaceholderFragment()).commit();
    }
}

@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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    int c=0;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
            false);

        Button add = (Button) rootView.findViewById(R.id.bAdd);
        TextView display = (TextView) rootView.findViewById(R.id.tvDisplay);

        add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                c+=1;
                display.setText("You're total is: " + c);
                //you don't need to set same content view again
                //setContentView(R.layout.activity_main);
            }
        });

        return rootView;
    }
}
}

edited Jun 26 '14 at 21:27

answered Jun 26 '14 at 20:50

Zoran

1,484
1
10
13

Creat a new onCreateView? or to replace it in the exist onCreateView? – iYonatan Jun 26 '14 at 20:57
Well, just put the code in onCreateView like i did and remove it from onCreate – Zoran Jun 26 '14 at 20:58
ok Im trying this now. i'll leave here a comment if it works or not. – iYonatan Jun 26 '14 at 21:00
Ok, basically it works, but there is no nothing: http://prntscr.com/3wti09 and there's suppose to be this: http://i.imgur.com/31twtNN.png – iYonatan Jun 26 '14 at 21:10
Did you remove setContentView(R.layout.activity_main); from onClick and did you remove button and textview from activity? – Zoran Jun 26 '14 at 21:13
that's how my code looks like: http://prntscr.com/3wtmlx I think i removed them – iYonatan Jun 26 '14 at 21:18
But whole code i wrote should be inside PlaceholderFragment, not inside activity. I'll have to do whole code... – Zoran Jun 26 '14 at 21:21
Oh ok, Im checking it now. – iYonatan Jun 26 '14 at 21:28
I edited everything. Try now – Zoran Jun 26 '14 at 21:28
You're welcome. Just vote for my answer ;) – Zoran Jun 26 '14 at 21:35

Android Developing App crashes

1 Answers1