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PONullPointerException when adding a TabListener
 

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  1. PONullPointerException when adding a TabListener
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    <p>I get this error message in LogCat:</p> <blockquote> <p>06-25 15:17:34.495: E/AndroidRuntime(5891): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.MainActivity}: <strong>java.lang.NullPointerException</strong> 06-25 16:07:43.589: E/AndroidRuntime(6587): Caused by: java.lang.NullPointerException 06-25 16:07:43.589: E/AndroidRuntime(6587): <strong>at com.example.MyTabsListener.onTabSelected(MyTabListener.java:28)</strong></p> </blockquote> <p>This is my main activity:</p> <pre><code>package com.example; import android.content.Context; import android.os.Bundle; import android.support.v4.app.Fragment; import com.actionbarsherlock.app.ActionBar; import com.actionbarsherlock.app.SherlockActivity; public class MainActivity extends SherlockActivity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ActionBar actionbar = getSupportActionBar(); actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); ActionBar.Tab tab1 = actionbar.newTab().setText("Fragment A"); SherlockFragment fragment1 = new AFragment(); tab1.setTabListener(new MyTabsListener(fragment1, this .getApplicationContext())); actionbar.addTab(tab1); } } </code></pre> <p>And my simple TabListener:</p> <pre><code>package com.example; import android.content.Context; import android.support.v4.app.FragmentTransaction; import android.widget.Toast; import com.actionbarsherlock.app.ActionBar; import com.actionbarsherlock.app.ActionBar.Tab; import com.actionbarsherlock.app.SherlockFragment; class MyTabsListener implements ActionBar.TabListener {     public SherlockFragment fragment;     private final Context appContext;     public MyTabsListener(SherlockFragment fragment, Context ctx) {         this.fragment = fragment;         this.appContext = ctx;     }     @Override     public void onTabReselected(Tab tab, FragmentTransaction ft) {         Toast.makeText(this.appContext, "Reselected!", Toast.LENGTH_LONG)                 .show();     }     @Override     public void onTabSelected(Tab tab, FragmentTransaction ft) {         ft.replace(R.id.fragment_container, fragment);     }     @Override     public void onTabUnselected(Tab tab, FragmentTransaction ft) {         ft.remove(fragment);     } } </code></pre> <p>And finally my class <em>Fragment A</em>:</p> <pre><code>package com.example; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import com.actionbarsherlock.app.SherlockFragment; public class AFragment extends SherlockFragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.weekdays, container, false); } } </code></pre> <p>So this function is causing the error in the TabListener:</p> <pre><code>@Override public void onTabSelected(Tab tab, FragmentTransaction ft) { ft.replace(R.id.fragment_container, fragment); } </code></pre>
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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