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POImageButton and NullPointerException
 

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    <p>Could I get a NullPointerException because the button I am referencing is nested inside several layouts? Any time I reference browseEditBtn I get an exception. It's a simple button! Come'on.</p> <pre><code>&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;TableLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal" android:stretchColumns="*"&gt; &lt;!-- &lt;include layout="@layout/mydesctextview" /&gt; --&gt; &lt;TableRow android:id="@+id/tableRow1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal"&gt; &lt;TextView android:text="TextView" android:layout_width="wrap_content" android:layout_gravity="left|center_vertical" android:id="@+id/txtItem" android:textSize="20dip" &gt;&lt;/TextView&gt; &lt;ImageButton android:src="@drawable/editbtn" android:layout_marginRight="10dip" android:layout_gravity="right|center_vertical" android:id="@+id/browseEditBtn" android:background="@drawable/my_group_statelist" &gt;&lt;/ImageButton&gt; &lt;/TableRow&gt; &lt;/TableLayout&gt; &lt;/LinearLayout&gt; </code></pre> <p>Source Code <em>(The Button is called in the main onCreate())</em>:</p> <pre><code>public class BrowseActivity extends ExpandableListActivity { final private String[] asColumnsToReturn = { Items.ITEMS_TABLE_NAME + "." + Items.ITEMS_ITEM, Items.ITEMS_TABLE_NAME + "." + Items.ITEMS_DESC, Items.ITEMS_TABLE_NAME + "." + Items.ITEMS_MANU, Items.ITEMS_TABLE_NAME + "." + Items.ITEMS_ID }; @SuppressWarnings("unchecked") @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.browse); DbHelper dbh = new DbHelper(this.getApplicationContext()); SQLiteDatabase db = dbh.getWritableDatabase(); SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); queryBuilder.setTables(Items.ITEMS_TABLE_NAME); ExpandableListView browseView = (ExpandableListView) findViewById(android.R.id.list); Button editBrowseBtn = (Button) findViewById(R.id.browseEditBtn); Cursor mCursor = queryBuilder.query(db, asColumnsToReturn, null, null, null, null, Items.DEFAULT_SORT_ORDER); startManagingCursor(mCursor); SimpleExpandableListAdapter mAdapter = new SimpleExpandableListAdapter( this, createGroup(), R.layout.row, R.layout.row, new String[] { Items.ITEMS_ITEM, Items.ITEMS_DESC }, new int[] { R.id.txtItem, R.id.dscItem }, createChildren(), R.layout.exprow, new String[] { Items.ITEMS_DESC, Items.ITEMS_MANU }, new int[] { R.id.dscItem, R.id.manuItem }); browseView.setAdapter(mAdapter); editBrowseBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(BrowseActivity.this, EditItemActivity.class); startActivity(intent); } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); menu.add("Add Item").setIntent(new Intent(this, AddItemActivity.class)); return super.onCreateOptionsMenu(menu); } @SuppressWarnings("rawtypes") public List createGroup() { DbHelper dbh = new DbHelper(this.getApplicationContext()); SQLiteDatabase db = dbh.getWritableDatabase(); SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); queryBuilder.setTables(Items.ITEMS_TABLE_NAME); Cursor mCursor = queryBuilder.query(db, new String[] { Items.ITEMS_ITEM, Items.ITEMS_DESC }, null, null, null, null, Items.DEFAULT_SORT_ORDER); startManagingCursor(mCursor); ArrayList&lt;HashMap&lt;String, String&gt;&gt; groupList = new ArrayList&lt;HashMap&lt;String, String&gt;&gt;(); mCursor.moveToFirst(); while (!(mCursor.isAfterLast())) { HashMap&lt;String, String&gt; groupMap = new HashMap&lt;String, String&gt;(); groupMap.put(Items.ITEMS_ITEM, mCursor.getString(mCursor.getColumnIndex(Items.ITEMS_ITEM))); groupMap.put(Items.ITEMS_DESC, mCursor.getString(mCursor.getColumnIndex(Items.ITEMS_DESC))); groupList.add(groupMap); mCursor.moveToNext(); } return (List) groupList; } @SuppressWarnings("rawtypes") public List createChildren() { DbHelper dbh = new DbHelper(this.getApplicationContext()); SQLiteDatabase db = dbh.getWritableDatabase(); SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); queryBuilder.setTables(Items.ITEMS_TABLE_NAME); Cursor mCursor = queryBuilder.query(db, new String[] { Items.ITEMS_ITEM, Items.ITEMS_DESC, Items.ITEMS_MANU }, null, null, null, null, Items.DEFAULT_SORT_ORDER); startManagingCursor(mCursor); mCursor.moveToFirst(); ArrayList&lt;ArrayList&lt;HashMap&lt;String, String&gt;&gt;&gt; childList = new ArrayList&lt;ArrayList&lt;HashMap&lt;String, String&gt;&gt;&gt;(); while (!(mCursor.isAfterLast())) { ArrayList&lt;HashMap&lt;String, String&gt;&gt; childListDesc = new ArrayList&lt;HashMap&lt;String, String&gt;&gt;(); for (int i = 0; i &lt; 1; i++) { HashMap&lt;String, String&gt; childMap = new HashMap&lt;String, String&gt;(); childMap.put(Items.ITEMS_DESC, mCursor.getString(mCursor .getColumnIndex(Items.ITEMS_DESC))); childMap.put(Items.ITEMS_MANU, mCursor.getString(mCursor .getColumnIndex(Items.ITEMS_MANU))); childListDesc.add(childMap); } childList.add(childListDesc); mCursor.moveToNext(); } return (List) childList; } } </code></pre> <p>And finally the logcat, I think...</p> <blockquote> <p>06-30 13:01:29.390: ERROR/AndroidRuntime(9189): FATAL EXCEPTION: main 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.simplyDesign.mdk/com.simplyDesign.mdk.BrowseActivity}: java.lang.NullPointerException 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.os.Handler.dispatchMessage(Handler.java:99) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.os.Looper.loop(Looper.java:123) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread.main(ActivityThread.java:4627) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at java.lang.reflect.Method.invokeNative(Native Method) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at java.lang.reflect.Method.invoke(Method.java:521) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at dalvik.system.NativeStart.main(Native Method) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): Caused by: java.lang.NullPointerException 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at com.simplyDesign.mdk.BrowseActivity.onCreate(BrowseActivity.java:62) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 06-30 13:01:29.390: ERROR/AndroidRuntime(9189): ... 11 more</p> </blockquote> <p><strong>edit_01</strong></p> <pre><code>public void doAction(View v) { startActivity(new Intent(getApplicationContext(), EditItemActivity.class)); } </code></pre> <p>I have used other buttons in the past to point to EditItemActivity and they have worked fine.</p>
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    1. COShow us the code where you reference it and have a problem. Also, try going to Project -> Clean first if you're developing in Eclipse.
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    2. COadd the stack of the exception that you have on the logcat, and add the part of code in your activity which is the source of the problem
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    3. COCan you post the code you're trying to retrieve the button with? Can't really help much without it.
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