# Problems using MidiKeyboardComponent (resolved!)

**URL:** <https://forum.juce.com/t/problems-using-midikeyboardcomponent-resolved/12189>\
**Category:** General JUCE discussion\
**Created:** [January 12, 2014, 10:52am UTC](https://forum.juce.com/t/problems-using-midikeyboardcomponent-resolved/12189 "2014-01-12T10:52:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![imekon](https://avatars.discourse-cdn.com/v4/letter/i/3da27b/32.png) [@imekon](https://forum.juce.com/u/imekon)\
**Post date:** [January 12, 2014, 10:52am UTC](https://forum.juce.com/t/problems-using-midikeyboardcomponent-resolved/12189/1 "2014-01-12T10:52:02Z")

</div>

I'm seeing a problem using MidiKeyboardComponent. I've copied code out of the demo and ended up with this MainContentComponent:

**The header MainContentComponent.h**

```
class MainContentComponent : public Component
{
public:
    //==============================================================================
    MainContentComponent();
    ~MainContentComponent();
    void paint (Graphics&) override;
    void resized() override;
private:
    MidiKeyboardComponent keyboard;
    MidiKeyboardState state;
    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MainContentComponent)
};
```

**The source: MainContentComponent.cpp**

```
MainContentComponent::MainContentComponent() 
    : keyboard(state, MidiKeyboardComponent::horizontalKeyboard)
{
    addAndMakeVisible(keyboard);
    setSize (800, 600);
}

MainContentComponent::~MainContentComponent()
{
}

void MainContentComponent::paint (Graphics& g)
{
    g.fillAll (Colour (0xffeeddff));
}

void MainContentComponent::resized()
{
    keyboard.setBounds(0, getHeight() - 64, getWidth(), 64);
}
```

The problem is when I run I get the following:

```
First-chance exception at 0x00594270 in SynthesizerSample.exe: 0xC0000005: Access violation reading location 0xCDCDCDCD.
Unhandled exception at 0x00594270 in SynthesizerSample.exe: 0xC0000005: Access violation reading location 0xCDCDCDCD.\> SynthesizerSample.exe!juce::Array\<juce::MidiKeyboardStateListener \*,juce::DummyCriticalSection,0\>::contains(juce::MidiKeyboardStateListener \* elementToLookFor) Line 374 C++SynthesizerSample.exe!juce::Array<juce::MidiKeyboardStateListener *,juce::DummyCriticalSection,0>::addIfNotAlreadyThere(juce::MidiKeyboardStateListener * newElement) Line 533 C++
     SynthesizerSample.exe!juce::MidiKeyboardState::addListener(juce::MidiKeyboardStateListener * listener) Line 177 C++
     SynthesizerSample.exe!juce::MidiKeyboardComponent::MidiKeyboardComponent(juce::MidiKeyboardState & s, juce::MidiKeyboardComponent::Orientation o) Line 100 C++
```

I just realised what the actual problem is - the order of the declarations. I had:

```
MidiKeyboardComponent keyboard;
MidiKeyboardState state;
```

When I switched the order:

```
MidiKeyboardState state;
MidiKeyboardComponent keyboard;
```

The problem goes away! I'm guessing state is being used before it's constructor has executed, hence the 0xCDCDCDCD.

---

<div class="post-metadata">

**Author:** ![DvdBr3o](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/dvdbr3o/32/12907_2.png) [@DvdBr3o](https://forum.juce.com/u/DvdBr3o)\
**Post date:** [April 14, 2022, 4:34am UTC](https://forum.juce.com/t/problems-using-midikeyboardcomponent-resolved/12189/2 "2022-04-14T04:34:19Z")

</div>

THX A LOTTTTT!!!  
As a green hand, i’ve been confused by the trouble for an entire morning…