While compiling an Android app, I am getting a warning telling me that my LinearLayout has an invalid child element, an ImageButton. I can’t quite figure out why this is happening. the full error is here:
Warning 1 The element ‘LinearLayout’ has invalid child element ‘ImageButton’. List of possible elements expected: 'Theme, Window, AlertDialog, FragmentAnimation, WindowAnimation, View, ViewGroup, ViewStub, InputMethod, SpellChecker, AccessibilityService, ActionMenuItemView, AbsListView, AbsSpinner, AnalogClock, Button, Chronometer, CompoundButton, CheckedTextView, EditText, FrameLayout, ExpandableListView, Gallery, GridView, ImageSwitcher, ImageView, ToggleButton, RelativeLayout, LinearLayout, GridLayout, ListView, PreferenceFrameLayout, MenuView, IconMenuView, ProgressBar, SeekBar, StackView, RatingBar, RadioGroup, TableLayout, TableRow, TabWidget, TextAppearance, TextSwitcher, TextView, TextViewAppearance, SelectionModeDrawables, SuggestionSpan, InputExtras, AutoCompleteTextView, PopupWindow, ViewAnimator, ViewFlipper, AdapterViewAnimator, AdapterViewFlipper, ViewSwitcher, ScrollView, HorizontalScrollView, Spinner, DatePicker, TwoLineListItem, SlidingDrawer, GestureOverlayView, QuickContactBadge, RotarySelector, WeightedLinearLayout, CalendarView, NumberPicker, TimePicker, Drawable, StateListDrawable, AnimationDrawa…
Any pointers as to why that is occurring? My layout file looks like this:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/question_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="24dp"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="@+id/true_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/true_button"/>
<Button
android:id="@+id/false_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/false_button"/>
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/previous_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/arrow_left"
android:contentDescription="@string/previous_button" />
<ImageButton
android:id="@+id/next_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/arrow_right"
android:contentDescription="@string/next_button" />
</LinearLayout>
</LinearLayout>