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Hello members of stackoverflow!
I worked successfully with the ViewPager (VP) on a "normal" activity.
Now I tried to use almost the same way for an Android Wear app.
In my MainActivity, which contains the VP, I faced different errors like:
- Error 1: (getFragmentManager() -> "Cannot be applied"
- Error 2: super(manager); -> "Cannot be applied"
- Error 3: public Fragment getItem(int i); -> "Incompatible return type"
I found this thread and was able to fix those errors by changing the imports + changing the build.gradle.
How to implement view pager in Android watch?
Those are now my imports in my MainActivity.java:
import android.app.Fragment;
import android.app.FragmentManager;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v13.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.wearable.activity.WearableActivity;
import java.util.ArrayList;
import java.util.List;
This is the rest of the MainActivity:
public class MainActivity extends WearableActivity
{
ViewPager vp; // Variable for Viewpager
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // Link to layout
ViewPager vp = findViewById(R.id.vp); // Link variable to ID
SetUpViewPager(vp); // Run viewpager method
}
public void SetUpViewPager(ViewPager viewpager)
{
MyViewPagerAdapter Adapter = new MyViewPagerAdapter(getFragmentManager());
Adapter.AddPageFragment(new Fragment1(), "Fragment1"); // Load page 1 inside of ViewPager
Adapter.AddPageFragment(new Fragment2(), "Fragment2"); // Load page 2 inside of ViewPager
viewpager.setAdapter(Adapter);
}
public class MyViewPagerAdapter extends android.support.v4.app.FragmentPagerAdapter
{
private List<Fragment> MyFragment = new ArrayList<>();
private List<String> MyPageTitle = new ArrayList<>();
public MyViewPagerAdapter(FragmentManager manager)
{
super(manager);
}
public void AddPageFragment(Fragment Frag, String Title)
{
MyFragment.add(Frag);
MyPageTitle.add(Title);
}
@Override
public Fragment getItem(int i)
{
return MyFragment.get(i);
}
@Nullable
@Override
public CharSequence getPageTitle(int position)
{
return MyPageTitle.get(position);
}
@Override
public int getCount()
{
return 2; // 2 pages total
}
}
}
Strange is that is says ViewPager vp; -> Field 'vp' is never used!
Fragment1: (Fragment2 is the same except for 2/two)
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment1 extends Fragment
{
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
{
View fragmentOne = inflater.inflate(R.layout.fragment1, container, false); // Link view and layout
return fragmentOne;
}
}
The XML files for the fragments are just constraint layouts with each 1 button. The content_main.xml contains the VP which accesses the activity_main.xml. I used the same way on the normal smartphone device and it worked flawlessly.
The problem is that everytime I start the app on the Wear Emulator, it immediately crashes.
This is what Logcat says:
10-23 14:40:32.909 2203-2203/com.example.user.wearvp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.wearvp, PID: 2203
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.user.wearvp/com.example.user.wearvp.MainActivity}: java.lang.NullPointerException:
Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5422)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException:
Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference
at com.example.user.wearvp.MainActivity.SetUpViewPager(MainActivity.java:35)
at com.example.user.wearvp.MainActivity.onCreate(MainActivity.java:24)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5422)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Any help will be appreciated!
P.S:
If I forgot to mention anything important, please, just ask and I will give you the needed information!
Best regards
