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Android ViewPager not Showing

I am trying to make a little app to try out some things for a bigger app I am developing. I want to add a viewpager that displays four images, I developed this viewpager alone and it worked, but when I tried to add it to my other app (with just a couple of buttons) with the tag, it does not show anything and I am really stuck in here. Is possible to add the Viewpager this way? Honestly I don't have that much experience in Java, I usually program only C and Assembler and I will be reaaally glad if you could help me.
This is the xml file with the button and the include:
<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:weightSum="1">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Calculo Rapido"
android:id="#+id/btcr"
android:layout_gravity="center_vertical"
android:layout_weight="0.16"
android:layout_alignParentStart="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Calculo Avanzado"
android:id="#+id/button"
android:layout_centerVertical="true"
android:layout_below="#+id/btcr" />
<include layout="#layout/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerHorizontal="true"
android:translationZ="15dp" />
Now, the MainActivity, which holds the button activity because I kept the Viewpager inside an Activity that's linked with the viewpager original layout
Button siguiente;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
siguiente = (Button)findViewById(R.id.btcr);
siguiente.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent siguiente = new Intent(MainActivity.this, Main2Activity.class);
startActivity(siguiente);
}
});
}
And lastly, the code for the mainpager main activity, this uses a CustomPagerAdapter saved in another java class. As I told before, this viewpager does work alone, but when I try to implement it here, with the /include tag, it doesn't show anything.
public class MainActivity extends Activity {
CustomPagerAdapter mCustomPagerAdapter;
ViewPager mViewPager;
private static int currentPage = 0;
private static int NUM_PAGES = 0;
Button siguiente;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// == Setting up the ViewPager ==
mCustomPagerAdapter = new CustomPagerAdapter(this);
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mCustomPagerAdapter);
final Handler handler = new Handler();
final Runnable Update = new Runnable() {
public void run() {
if (currentPage == NUM_PAGES) {
currentPage = 0;
}
mViewPager.setCurrentItem(currentPage++);
if (currentPage == 5) {
currentPage = 0;
mViewPager.setCurrentItem(currentPage++, false);
}
}
};
Timer swipeTimer = new Timer();
swipeTimer.schedule(new TimerTask() {
#Override
public void run() {
handler.post(Update);
}
}, 2000, 2000);
}
Sorry if it is too long guys, but I am a little frustrated, I have tried a lot of things but it isn't working yet. Either the buttons do their thing and the ViewPager doesn't work or the ViewPager works but the buttons are dead.
I will reaaally aprecciate your help :)

create a new xml file inside layout folder and name it secondactivity.xml
and put this code
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/pager">
</android.support.v4.view.ViewPager>
</LinearLayout>
Now inside your Main2Activity.class
change
setContentView(R.layout.activity_main);
to
setContentView(R.layout.secondactivity);
And remove the include from your previous xml

Turns out, what I needed was just the simple solution. I had to put the viewpager on my activity's layout file as another object, just configuring its size and position. And then, on my onCreate I pasted the code of my functioning ViewPager. Quite simple, without requiring another layouts :)

Issues when relative layout implement swipe-to-refresh layout

I'm currently attempting to implement swipe-to-refresh layout into relative layout, but it is extremely insensitive and unstable. When I pull down the screen, it usually either doesn't refresh or it refreshes without progress bar.
<android.support.v4.widget.SwipeRefreshLayout
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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.miaor.tutorialweather.MainActivity"
android:id="#+id/refreshLayout"
android:background="#fe970b">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
</RelativeLayout>
public class MainActivity extends AppCompatActivity{
public static final String TAG = MainActivity.class.getSimpleName();
#BindView(R.id.TimeString) TextView mTimeLabel;
#BindView(R.id.TemperatureLabel) TextView mTemperatureLabel;
#BindView(R.id.HumidityValue) TextView mHumidityValue;
#BindView(R.id.rainingChanceValue) TextView mChance;
#BindView(R.id.weatherIcon) ImageView mWeatherIcon;
#BindView(R.id.SummaryText) TextView mSummaryText;
#BindView(R.id.refreshLayout) SwipeRefreshLayout mSwipeRefreshLayout;
///why do we make a new variable of CurrentWeather
private CurrentWeather mCurrentWeather;
private String apiKey = "6b9448b8e21c2abe2fb623b25554a77c";
private double latitude = 31.230708;
private double longitude = 121.472916;
private String forecastUrl = "https://api.forecast.io/forecast/" + apiKey +
"/" + latitude + "," + longitude;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
///implement swipe-to-refresh feature
mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
Log.i(TAG, "onRefresh is working");
getForecast();
}
});
getForecast();
Log.d(TAG, "Main UI code is running!");
}

You can't implement SwipeToRefreshLayout with RelativeLayout as its child. You need to have a scrollable view as its only child. e.g. Listview, RecyclerView, ScrollView. That is the reason why it is not working as expected for you.

That is not the right position.
You need type like this:
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/your_id"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
YOUR RELATIVE LAYOUT HERE
</ScrollView>
</android.support.v4.widget.SwipeRefreshLayout>

Your code looks fine, it's weird that it's not working correctly... Maybe it's because of the ButterKnife library? I don't think that's the problem, but it will be worth the shot to get views manually to see if that's the problem
Then, if you need the loading animation to appear/hide you can use mSwipeRefreshLayout.setRefreshing(boolean);
For example in my app I attach the listener first (as you did in your example) and then I use the following code to show the loading animation while I fetch the data.
// Show loading while fetching the first set of data
mainSwipeRefreshLayout.post(new Runnable() {
#Override
public void run() {
mainSwipeRefreshLayout.setRefreshing(true);
}
});
In my fetchData() method I use the following line to hide the animation again when it finishes fetching the data.
// On load complete stop refresh animation
mainSwipeRefreshLayout.setRefreshing(false);
Hope this helps!
Andres.

The method findViewById(int) is undefined for the type Json.SnagInfo

So I set up a main_layout.xml shown below with 3 textviews which I then "setContentView" to the main_layout.xml from MainActivity.java as shown below. I then have methods which will be in Java.class (a seperate class in a seperate package) that won't be an activity but will have methods that will be called from MainActivity. The problem is I'm having trouble accessing any of these resources, each of the three findViewById's in Java.class get highlighted under in red and error states: The method findViewById(int) is undefined for the type Json.SnagInfo
What am I doing wrong?
main_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/title" />
<TextView
android:id="#+id/author"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/author" />
<TextView
android:id="#+id/release"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/release"/>
</LinearLayout>
MainActivity.java
public class MainActivity extends Activity {
// Local Variables
Context context;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
}
}
Json.java
public class Json {
TextView title;
TextView author;
TextView release;
ListView published;
ArrayList<HashMap<String, String>> bookList = new ArrayList<HashMap<String, String>>();
public class SnagInfo extends AsyncTask<URL, Void, String> {
protected void onPreExecute() {
super.onPreExecute();
bookList.clear();
title = (TextView) findViewById(R.id.title);
author = (TextView) findViewById(R.id.author);
release = (TextView) findViewById(R.id.release);
}
}
}

findViewById is a method of Activity class. SnagInfo extends AsyncTask.
If you want to the result of background computation in the activity class you can use interface as a Callback.
Now initialize all your views in activity and set the data there.
Check this link
How do I return a boolean from AsyncTask?
You can also make asynctask an inner class of activity and update ui in onPostExecute

Why is this static field null?

on android.
my activity is like this.
public class MainActivity extends Activity {
static TextView textview;
static int aaa = 1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.getWindow().setSoftInputMode(LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
setContentView(R.layout.activity_main);
textview = (TextView)findViewById(R.id.textView6);
//other method,startservice()and so on.
and there is BroadcastReceiver to receive a flag from service.
public static class Receiver extends BroadcastReceiver{
#Override
public void onReceive(Context context, Intent intents) {
intents.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
textview.setText("set")//throw null point
Log.d("aaa","aaa is" + aaa);
like this, in onReceiver, textview is null.
as test, int aaa is'nt null.
why textview is null?
EDIT
Texttiew xml is
<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"
tools:context=".MainActivity" >
<TextView
android:id="#+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/adview"
android:layout_alignParentLeft="true"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
And method in Activity using same textview.settext isnt null.
Thanks.
EDIT2
I can know i should save this variable.
So, whats the best way to save VIEW variable?
SharedPreferences seem not able to save VIEW variable.

This thread indicates that having static fields might be a problem.
In general, android kills your app.. and on return static variables may not be set.
static variable null when returning to the app

This is likely that you are not referencing the correct textview element. Double check your IDs in your layout file.

Why Fragment cannot be public static class?

I came across such problem: I wanted to have some Fragment as public static member of my Activity class.
But when I put such Fragment to layout file I receive such exception:
Caused by: android.support.v4.app.Fragment$InstantiationException:
Unable to instantiate fragment com.tst.MainActivity.InnerFragment:
make sure class name exists, is public,
and has an empty constructor that is public
...
My code looks like this:
package com.tst;
public final class MainActivity extends SherlockFragmentActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public static class InnerFragment extends SherlockFragment {
public InnerFragment() {
super();
}
...
}
}
Layout file looks like this:
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<fragment
android:id="#+id/inner_fragment"
android:name="com.tst.MainActivity.InnerFragment"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</LinearLayout>
Now my question is why such code throws this Exception? As Android should be able to instanitate InnerFragment as it is public static. What is more I used to use public static Fragments and they worked, but on that time I added them programmatically in code not in xml definition.
Regards,
Michal

Change
android:name="com.tst.MainActivity.InnerFragment"
to
android:class="com.tst.MainActivity$InnerFragment"