Develop Reference

error: cannot find symbol variable viewpager ---Androidx

I have the following code, the project is migrated to andoidx, R.id.viewpager returns can not find symbol variable viewpager SimpleFragmentPagerAdapter is a custom(an extention of)
FragmentPagerAdapter and is working well
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set the content of the activity to use the activity_main.xml layout file
setContentView(R.layout.activity_catagory);
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
// Create an adapter that knows which fragment should be shown on each page
SimpleFragmentPagerAdapter adapter = new SimpleFragmentPagerAdapter(getSupportFragmentManager());
// Set the adapter onto the view pager
viewPager.setAdapter(adapter);
}
}

getSupportActionBar() The method getSupportActionBar() is undefined for the type TaskActivity. Why?

I was recommended to extend my Activity class from ActionBarActivity
Here is the previous code:
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
I wrote new application and followed advice.
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
public class MainActivity extends ActionBarActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ActionBar actionBar =getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
If I use ACtionBarActivity instead of Activity, I get the following error on the phone, when I try to run it:
The method getSupportActionBar() is undefined for the type TaskActivity

Your class needs to extend from ActionBarActivity, rather than a plain Activity in order to use the getSupport*() methods.
Update [2015/04/23]: With the release of Android Support Library 22.1, you should now extend AppCompatActivity. Also, you no longer have to extend ActionBarActivity or AppCompatActivity, as you can now incorporate an AppCompatDelegate instance in any activity.

Here is another solution you could have used. It is working in my app.
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
android.support.v7.app.ActionBar actionBar =getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_main)
Then you can get rid of that import for the one line ActionBar use.

If you are already extending from ActionBarActivity and you are trying to get the action bar from a fragment:
ActionBar mActionBar = (ActionBarActivity)getActivity()).getSupportActionBar();

Here is the answer of my question.
I've asked that again with some remarks.
How to add support libraries?

If you are extending from an AppCompatActivity and are trying to get the ActionBar from the Fragment, you can do this:
ActionBar mActionBar = ((AppCompatActivity) getActivity()).getSupportActionBar();

You have to change the extends Activity to extends
AppCompactActivity then try set and getSupportActionBar()

Can you set the ActionBar before you set the Contient View? This order would be better:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActionBar actionBar =getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
}

method getfragmentmanager() is undefined

I am making a view pager to make a slide show for images. I took code from Android developers, but I was facing some issues, fragment was not recognized, I think it was because my android was 2.33. So to solve that I imported a jar file android.support.v4.jar
My issues were resolved but now I am getting this error that getfragmentmanager() is undefined
and another issue "The method invalidateOptionsMenu() is undefined for the type new ViewPager.SimpleOnPageChangeListener(){}"
Here is my code, can any one please help ??
My platform is 2.3.3 and api level is 10 and in manifest I have this
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
Code :
package com.example.profilemanagment;
import android.support.v4.app.Fragment;
import android.support.v4.app.*;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.NavUtils;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;
public class ScreenSlideActivity extends FragmentActivity {
/**
* The number of pages (wizard steps) to show in this demo.
*/
private static final int NUM_PAGES = 5;
/**
* The pager widget, which handles animation and allows swiping horizontally to access previous
* and next wizard steps.
*/
private ViewPager mPager;
/**
* The pager adapter, which provides the pages to the view pager widget.
*/
private PagerAdapter mPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_screen_slide);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getFragmentManager());
mPager.setAdapter(mPagerAdapter);
mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// When changing pages, reset the action bar actions since they are dependent
// on which page is currently active. An alternative approach is to have each
// fragment expose actions itself (rather than the activity exposing actions),
// but for simplicity, the activity provides the actions in this sample.
invalidateOptionsMenu();
}
});
}
/**
* A simple pager adapter that represents 5 {#link ScreenSlidePageFragment} objects, in
* sequence.
*/
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return ScreenSlidePageFragment.create(position);
}
#Override
public int getCount() {
return NUM_PAGES;
}
}
}

Quoting from the docs.
When using this class (FragmentActivity) as opposed to new platform's built-in fragment and loader support, you must use the getSupportFragmentManager() and getSupportLoaderManager() methods respectively to access those features.
Since you are extending FragmentActivity use getSupportFragmentManager()
http://developer.android.com/reference/android/support/v4/app/FragmentActivity.html
Check the docs
FragmentActivity does not have getFragmentManager()

PreferenceFragment can't load from XML (ClassCastException)

I'm having some difficulties getting a PreferenceFragment to load using XML.
It keeps throwing a ClassCastException "PreferenceFragmentClass cannot be cast to android.support.v4.app.Fragment".
The code is intended to run on API14 and higher.
Here's my code:
import android.os.Bundle;
import android.preference.PreferenceFragment;
public class SettingsFragment extends PreferenceFragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);
}
}
Here's the code where SettingsFragment is being used in:
import android.app.ActionBar;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
public class FragmentsSetup extends FragmentActivity {
private ViewPager viewPager;
private TabsAdapter tabsAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
viewPager = new ViewPager(this);
viewPager.setId(R.id.pager);
setContentView(viewPager);
final ActionBar actionBar = getActionBar();
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
tabsAdapter = new TabsAdapter(this, viewPager);
tabsAdapter.addTab(actionBar.newTab().setText(getString(R.string.forwarding_tab).toUpperCase()), ForwardingFragment.class, null);
tabsAdapter.addTab(actionBar.newTab().setText(getString(R.string.settings_tab).toUpperCase()), SettingsFragment.class, null);
}
}
Any tips would be greatly appreciated.

SettingsFragment inherits from PreferenceFragment. PreferenceFragment is from the native API Level 11 implementation of fragments. However, FragmentsSetup is inheriting from FragmentActivity, from the Android Support package's backport of fragments.
That combination will not work.
If you intend to support devices older than API Level 11, you cannot use PreferenceFragment. Also, I am uncertain if PreferenceFragment works outside of a PreferenceActivity (it might, but I have never tried that).

If you're developing for Android 3.0 (API level 11) and higher, you should use a PreferenceFragment to display your list of Preference objects.
Also you can add a PreferenceFragment to any activity—you don't need to use PreferenceActivity.
See documentation here:
https://developer.android.com/guide/topics/ui/settings.html?

Android Actionbar + FragmentActivity

In my application i have tabs but now i need to add Sherlock Actionbar i know that I need use extends SherlockActivity but early I had FragmentActivity how to fix it ?
public class MainActivity extends SherlockActivity {
Now I have error here beacuse i don't have FragmentActivity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
Error:
The method getSupportFragmentManager() is undefined for the type MainActivity

There is SherlockFragmentActivity, I believe, you can extend from that