Q:

Can't get .getwidth() and .getheight() to work

I know there have been a lot of other questions on this topic, but I've looked through all of them, and still not gotten it to work.
I've made this code for testing:
public class MainActivity extends Activity {

RelativeLayout layout;
TextView widthtext;
TextView heighttext;
int width;
int height;

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

    layout = (RelativeLayout) findViewById(R.id.rela);

    widthtext = (TextView) findViewById(R.id.textView);
    heighttext = (TextView) findViewById(R.id.textView2);

    layout.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            width = layout.getWidth();
            height = layout.getHeight();
        }
    });

    widthtext.setText(width);
    heighttext.setText(height);
}

and
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
android:id="@+id/rela">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="123"
    android:id="@+id/textView"
    android:layout_alignTop="@+id/textView2"
    android:layout_toLeftOf="@+id/textView2"
    android:layout_toStartOf="@+id/textView2"
    android:layout_marginRight="50dp"
    android:layout_marginEnd="50dp" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="123"
    android:id="@+id/textView2"
    android:layout_marginRight="50dp"
    android:layout_marginEnd="50dp"
    android:layout_centerVertical="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true" />

After a lot of hassle I've now notised that the width and height int's have the right values, though I can't make them display in my TextViews, getting the NullPointerExeption.
Anyone who can make this work?
EXTRA:
public class MainActivity extends Activity {

RelativeLayout layout;
TextView widthtext;
TextView heighttext;
int width;
int height;

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

    layout = (RelativeLayout) findViewById(R.id.rela);

    widthtext = (TextView) findViewById(R.id.textView);
    heighttext = (TextView) findViewById(R.id.textView2);

    layout.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            width = layout.getWidth();
            height = layout.getHeight();
        }
    });

    widthtext.setText(width + "");
    heighttext.setText(height + "");
}

}

A:

You are doing this
widthtext.setText(width);
heighttext.setText(height);

outside of your listener so naturally it doesn't have the values yet.
Move them inside
layout.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
        width = layout.getWidth();
        height = layout.getHeight();

        // move here
        widthtext.setText(width);
        heighttext.setText(height);
    }
});
}

As blackbelt pointed out in a comment, you are calling setText() and passing an int. This will look for a resource id of that value. Change those to Strings. 
widthtext.setText("" + width);
heighttext.setText("" + height);

