CreateGridPatterentBrush的ID2D1RenderTarget* pRenderTarget调用CreateCompatibleRenderTarget 出现this 是 nullptr怎么解决？

Question

ID2D1RenderTarget* m_pRenderTarget;

ID2D1RenderTarget* pRenderTarget;

ID2D1BitmapBrush** ppBitmapBrush;

ID2D1BitmapRenderTarget* pCompatibleRenderTarget;

ID2D1Bitmap* pBitmap;

HRESULT CreateGridPatterentBrush(ID2D1RenderTarget* pRenderTarget,ID2D1BitmapBrush** ppBitmapBrush);

HRESULT CMainWindow::CreateGridPatterentBrush(ID2D1RenderTarget* pRenderTarget, ID2D1BitmapBrush** ppBitmapBrush)

{

//ID2D1BitmapRenderTarget *pCompatibleRenderTarget = NULL;

HRESULT hr = pRenderTarget->CreateCompatibleRenderTarget(D2D1::SizeF(10.0f, 10.0f),&pCompatibleRenderTarget);

if (SUCCEEDED(hr))

{

    // Draw a pattern.

    ID2D1SolidColorBrush *pGridBrush = NULL;

    hr = pCompatibleRenderTarget->CreateSolidColorBrush(

        D2D1::ColorF(D2D1::ColorF(0.93f, 0.94f, 0.96f, 1.0f)),

        &pGridBrush

        );

    if (SUCCEEDED(hr))

    {

        pCompatibleRenderTarget->BeginDraw();

        pCompatibleRenderTarget->FillRectangle(D2D1::RectF(0.0f, 0.0f, 10.0f, 1.0f), pGridBrush);

        pCompatibleRenderTarget->FillRectangle(D2D1::RectF(0.0f, 0.1f, 1.0f, 10.0f), pGridBrush);

        pCompatibleRenderTarget->EndDraw();

        // Retrieve the bitmap from the render target.

        ID2D1Bitmap *pGridBitmap = NULL;

        hr = pCompatibleRenderTarget->GetBitmap(&pGridBitmap);

        if (SUCCEEDED(hr))

        {

            // Choose the tiling mode for the bitmap brush.

            D2D1_BITMAP_BRUSH_PROPERTIES brushProperties =

                D2D1::BitmapBrushProperties(D2D1_EXTEND_MODE_WRAP, D2D1_EXTEND_MODE_WRAP);

            // Create the bitmap brush.

            hr = m_pRenderTarget->CreateBitmapBrush(pGridBitmap, brushProperties, ppBitmapBrush);        

            pGridBitmap->Release();

        }

        pGridBrush->Release();

    }

    pCompatibleRenderTarget->Release();

}

return hr;

return E_NOTIMPL;
```}
void CMainWindow::OnPaint()

{

    CPaintDC dc(this); 

    

    this->CreateGridPatterentBrush(pRenderTarget,ppBitmapBrush);

    

}

Answer 1

您好，

示例中使用的是

HRESULT DemoApp::CreateGridPatternBrush(

ID2D1RenderTarget *pRenderTarget,

ID2D1BitmapBrush **ppBitmapBrush

)
{


HRESULT hr = S_OK;

// Create a compatible render target.

ID2D1BitmapRenderTarget *pCompatibleRenderTarget = NULL;

hr = pRenderTarget->CreateCompatibleRenderTarget(

    D2D1::SizeF(10.0f, 10.0f),

    &pCompatibleRenderTarget

    );  

没有hr变量，if (SUCCEEDED(hr))为什么没有提示编译错误？

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