Strange @hide behavior

Question

In BitmapFactory.decodeStream method :

public static Bitmap decodeStream(InputStream is, Rect outPadding, Options opts) {
        // we don't throw in this case, thus allowing the caller to only check
        // the cache, and not force the image to be decoded.
        if (is == null) {
            return null;
        }

        Bitmap bm = null;

        Trace.traceBegin(Trace.TRACE_TAG_GRAPHICS, "decodeBitmap");
        try {
            if (is instanceof AssetManager.AssetInputStream) {
                final int asset = ((AssetManager.AssetInputStream) is).getAssetInt();
                bm = nativeDecodeAsset(asset, outPadding, opts);
            } else {
                bm = decodeStreamInternal(is, outPadding, opts);
            }

            if (bm == null && opts != null && opts.inBitmap != null) {
                throw new IllegalArgumentException("Problem decoding into existing bitmap");
            }

            setDensityFromOptions(bm, opts);
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_GRAPHICS);  // THAT IS COLLISION LINE
        }

        return bm;
    }

we see a usage Trace.TRACE_TAG_GRAPHICS. Ok, let's look at Trace.java :

public final class Trace {
    /*
     * Writes trace events to the kernel trace buffer.  These trace events can be
     * collected using the "atrace" program for offline analysis.
     */

    private static final String TAG = "Trace";

    // These tags must be kept in sync with system/core/include/cutils/trace.h.
    /** @hide */
    public static final long TRACE_TAG_NEVER = 0;
    /** @hide */
    public static final long TRACE_TAG_ALWAYS = 1L << 0;
    /** @hide */
    public static final long TRACE_TAG_GRAPHICS = 1L << 1;
    ...

And when i try to use Trace.TRACE_TAG_GRAPHICS flag compiler give me error that this tag not responsible for me. I agree with him.

But the question - Why BitmapFactory have access to @hide variables and why me not?

That's what @hide does. It prevent third party developers from accessing stuff in the framework. — njzk2, Mar 21 '14 at 13:09
I disagree with you. Look at the https://code.google.com/p/doclava/wiki/JavadocTags#@hide — Sergey Shustikov, Mar 21 '14 at 13:10
for having compiled regular and unhidden android versions, I can tell you for a fact that @hide stuff are not included in the published API. (which you can see for yourself as you can see that you cannot compile against them) — njzk2, Mar 21 '14 at 13:19
the answer to the duplicate question does answer your question, I think. — njzk2, Mar 21 '14 at 14:07

score 0 · Answer 1 · answered Mar 21 '14 at 13:10

For private APIs, that are not part of the published, official Android API, Android uses the @hide annotation to prevent them from being included in the jar that your program is compiled against. There is no guarantee that these will be available in the future so you shouldn't rely on them. If you need to use it, you can access it via Reflection.

Strange @hide behavior

1 Answers1