Android application would not stop crashing despite its simplicity

Question

I am currently making a very very simple Android app, following this tutorial: http://www.mkyong.com/android/android-textbox-example/

In my fragment_main.xml, I have this:

<EditText
    android:id="@+id/editText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <requestFocus />
</EditText>

In my MainActivity.java, I have the following. It's simply an app that responds to key presses.

private EditText edittext;

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

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

    addKeyListener();
}

public void addKeyListener()
{
    // get edittext component
    edittext = (EditText) findViewById(R.id.editText);

    // add a keylistener to keep track of user input

    edittext.setOnKeyListener(new View.OnKeyListener()
    {

        @Override
        public boolean onKey(View v, int keyCode, KeyEvent event)
        {
            if((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER))
            {
                // display a floating message
                Toast.makeText(MainActivity.this, edittext.getText(), Toast.LENGTH_LONG).show();
                return true;
            }
            else if((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_9))
            {
                // display a floating message
                Toast.makeText(MainActivity.this, "Number 9 is pressed!", Toast.LENGTH_LONG).show();
                return true;
            }
            return false;
        }
    });
}

The app basically responds to key presses.

Everything I have up top are the only things I have changed from the stock application. The target was 4.3 on my Note 3.

My app runs fine if it is a Hello World app (the stock app you create with Eclipse), however, as soon as I add additional components/methods to it, it would simple get me unfortunately, myapp has stopped.

I have tried creating a new project just for this new example, but the same errors of the application crashing.

I was wondering does anyone know why this is happening. Compilation does not tell me any warnings/errors.

https://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this — CommonsWare, May 27 '14 at 23:51
It appears this may be of relevance: http://puu.sh/949Zg/67d8f3228e.png — theGreenCabbage, May 28 '14 at 00:57
I guess this is due to NullPointerException since first: your contentView is the activity_main layout and your fragment is fragment_main layout where the EditText is placed. Since that one is a fragment you also need to get the layout out there. Try locating your class that extends that Fragment and apply it from there. — KaHeL, May 28 '14 at 03:40

score 2 · Accepted Answer · answered May 28 '14 at 03:37

2

The error is :

edittext = (EditText) findViewById(R.id.editText);

because editText component is in fragment_main.xml , not the current activity's contentview activity_main.xml, so the value of variable edittext must be null, then the following code will cause error.

please move the method addKeyListener() into PlaceholderFragment class, then it will be ok.

answered May 28 '14 at 03:37

lxh2002

36
2

Exactly, also the Tutorial he shared is already outdated. That one doesn't implement a Fragment at all. – KaHeL May 28 '14 at 03:42
Hi lxh2002. Where do I call `addKeyListener()`? – theGreenCabbage May 28 '14 at 18:15
I also implemented `addKeyListener()` within my previous class. Does this mean I also have to implement `addKeyListener()` within `fragment_view`'s static class? – theGreenCabbage May 28 '14 at 19:56

score 0 · Answer 2 · answered May 28 '14 at 04:47

0

I guess the solution is simple.Your EditText resides in fragment_main.xml and you are using activity_main with setContentView() in your java file.Hence there will be a nullpointer exception.The solution is :change setContentView(R.layout.activity_main); to setContentView(R.layout.fragment_main);

answered May 28 '14 at 04:47

kgandroid

5,507
5
39
69

Hi @kgandroid. Seems like your method is simpler than what the others suggested, that is putting stuff into `PlaceholderFragment`. I'll test it out on my phone soon. – theGreenCabbage May 28 '14 at 18:18

Android application would not stop crashing despite its simplicity

2 Answers2