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POHow to refer to activity element from viewpager
 

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  1. POHow to refer to activity element from viewpager
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    <p>I try to write an app, that is using slide effect for activities and found that ViewPager from Compatibility Package is what I need. I successfully made the slide, it works in the way i want, but my problem is that I am not able to refer to the elements in my Activity.</p> <p>This is my main.xml:</p> <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;android.support.v4.view.ViewPager android:id="@+id/pager" android:layout_width="match_parent" android:layout_height="match_parent" /&gt; &lt;/LinearLayout&gt; </code></pre> <p>MainActivity.java: </p> <pre><code>public class MainActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); MyPagerAdapter adapter = new MyPagerAdapter(); ViewPager myPager = (ViewPager) findViewById(R.id.pager); myPager.setAdapter(adapter); myPager.setCurrentItem(0); if (Fibonacci.getInstance().number != 0) displayResults(); ImageButton btnCalculate = (ImageButton) findViewById(R.id.btnCalculateDark); btnCalculate.setOnClickListener(new OnClickListener() { public void onClick(View arg0) { // do button click } }); } private class MyPagerAdapter extends PagerAdapter { public int getCount() { return 2; } public Object instantiateItem(View collection, int position) { LayoutInflater inflater = (LayoutInflater) collection.getContext() .getSystemService(Context.LAYOUT_INFLATER_SERVICE); int resId = 0; switch (position) { case 0: resId = R.layout.activity_dark; break; case 1: resId = R.layout.activity_pale; break; } View view = inflater.inflate(resId, null); ((ViewPager) collection).addView(view, 0); return view; } @Override public void destroyItem(View arg0, int arg1, Object arg2) { ((ViewPager) arg0).removeView((View) arg2); } @Override public boolean isViewFromObject(View arg0, Object arg1) { return arg0 == ((View) arg1); } @Override public Parcelable saveState() { return null; } } } </code></pre> <p>My problem is that I receive NullPointerEception for the following line:</p> <pre><code>ImageButton btnCalculate = (ImageButton) findViewById(R.id.btnCalculateDark); </code></pre> <p>I know it's because in setContentView I set up main.xml, and I want to refer to an element in activity_dark.xml or activity_pale.xml. Unfortunately i am not able to figure out how to refer to the element. Any hints would be appreciated! Thank you!</p>
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