Dynamically add views to the layout of a specific fragment

Question

I am trying to add a TextView dynamically to a layout that is part of a fragment, but it does not work. As soon as the application starts, it immediately shuts down. I think he should do something with TextView Paper = new TextView(this); part. I do not know how to get the correct Context , since I work with fragments. My guess may be wrong, but I really don't know where the error might be.

 public class PageFragment extends Fragment { private int fragmentNR; public PageFragment(int nr) { this.fragmentNR = nr; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v = new View(getActivity()); if (fragmentNR == 0) v = inflater.inflate(R.layout.page1, container, false); else if (fragmentNR == 1) v = inflater.inflate(R.layout.page2, container, false); else if (fragmentNR == 2) v = inflater.inflate(R.layout.page3, container, false); return v; } } 

 public class MainActivity extends FragmentActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); PageAdapter mPageAdapter = new PageAdapter(getSupportFragmentManager()); ViewPager mViewPager = (ViewPager) findViewById(R.id.viewpager); mViewPager.setAdapter(mPageAdapter); //This is where i try to add my TextView into my Layout LinearLayout PaperLayout = (LinearLayout) findViewById(R.id.PaperLayout);//PaperLayout is a LinearLayout within the Page2-Fragment(R.layout.page2) TextView Paper = new TextView(this); Paper.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); Paper.setText("Paper2"); PaperLayout.addView(Paper); } } 

Logcat

 07-18 16:32:58.330: E/AndroidRuntime(614): FATAL EXCEPTION: main 07-18 16:32:58.330: E/AndroidRuntime(614): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.loni.math_prime/com.loni.math_prime.MainActivity}: java.lang.NullPointerException 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.access$600(ActivityThread.java:130) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.os.Handler.dispatchMessage(Handler.java:99) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.os.Looper.loop(Looper.java:137) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.main(ActivityThread.java:4745) 07-18 16:32:58.330: E/AndroidRuntime(614): at java.lang.reflect.Method.invokeNative(Native Method) 07-18 16:32:58.330: E/AndroidRuntime(614): at java.lang.reflect.Method.invoke(Method.java:511) 07-18 16:32:58.330: E/AndroidRuntime(614): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 07-18 16:32:58.330: E/AndroidRuntime(614): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 07-18 16:32:58.330: E/AndroidRuntime(614): at dalvik.system.NativeStart.main(Native Method) 07-18 16:32:58.330: E/AndroidRuntime(614): Caused by: java.lang.NullPointerException 07-18 16:32:58.330: E/AndroidRuntime(614): at com.loni.math_prime.MainActivity.onCreate(MainActivity.java:30) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.Activity.performCreate(Activity.java:5008) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 07-18 16:32:58.330: E/AndroidRuntime(614): ... 11 more 

XML

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <android.support.v4.view.ViewPager android:id="@+id/viewpager" android:layout_width="fill_parent" android:layout_height="fill_parent" > <android.support.v4.view.PagerTitleStrip android:layout_width="fill_parent" android:layout_height="wrap_content" android:textSize="32dp" android:textStyle="bold" android:textColor="#fff5ee" android:layout_gravity="top" /> </android.support.v4.view.ViewPager> </LinearLayout> 

Answer 1

It is decided:

 public class PageFragment extends Fragment { private int fragmentNR; public PageFragment(int nr) { this.fragmentNR = nr; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v = new View(getActivity()); if (fragmentNR == 0) v = inflater.inflate(R.layout.page1, container, false); else if (fragmentNR == 1){ v = inflater.inflate(R.layout.page2, container, false); View tv = v.findViewById(R.id.Ausgabe); ((TextView)tv).setText("TestText"); View pl = v.findViewById(R.id.PageLayout); TextView Paper = new TextView(pl.getContext()); Paper.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); Paper.setText("Inserted TestText"); ((LinearLayout)pl).addView(Paper); } else if (fragmentNR == 2) v = inflater.inflate(R.layout.page3, container, false); return v; } }