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    <p>The graphics context returned by <code>UIGraphicsGetCurrentContext</code> in <code>drawRect:</code> is owned by the system and cleared at the start of a drawing pass. Create your own <code>CGContext</code> to record your drawing and render it to the <code>drawRect:</code> context as needed.</p> <p>Create a paired <code>CGBitmapContext</code> and <code>CGImage</code> that refer to the same <code>CGDataProvider</code> and have the same size, color space and other properties. Draw into that context when and how you see fit, then in <code>drawRect:</code> use <code>CGContextDrawImage</code> to display it.</p> <p>Or if you are just doing a series of lines, you can build a <code>CGMutablePath</code> and render it to the system context.</p> <p>Edit:</p> <p>Look at <code>CGImageCreate</code> and <code>CGBitmapContextCreate</code> in their respective header files. Most of the arguments are the same. The bitmap context expects a raw data pointer, while the image expects a CGDataProvider. Here is a rough sketch of what the code would look like. In the end you can draw into the context then use the image to render into another context.</p> <pre><code>size_t width = 400; size_t height = 300; CFMutableDataRef data = CFDataCreateMutable( NULL , width * height * 4 ); // 4 is bytes per pixel CGDataProviderRef provider = CGDataProviderCreateWithCFData( data ); CGImageRef image = CGImageCreate( width , height , ... , provider , ... ); CGBitmapContextRef context = CGBitmapContextCreate( CFDataGetMutableBytePtr( data ) , width , height , ... ); CFRelease( data ); // retained by provider I think CGDataProviderRelease( provider ); // retained by image </code></pre> <p>There are a lot of blanks to fill in, but this should get you started. You could use malloc instead of CFData for the buffer.</p>
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    1. COI guess I've got your idea. But I am not sure about CGDataProvider and is there example code for that?
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    2. COI have an implementation but it doesn't work as my expected. I guess my understanding is still on the wrong way? I have posted the code would you mind checking it?
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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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