关于Android Bitmap

说到内存和性能优化，都会谈到Bitmap，经常会谈到recycle()方法。但是又有人说不需要调用recycle().到底是什么情况呢？看源码注释，一目了然。

    /**     * Free the native object associated with this bitmap, and clear the     * reference to the pixel data. This will not free the pixel data synchronously;     * it simply allows it to be garbage collected if there are no other references.     * The bitmap is marked as "dead", meaning it will throw an exception if     * getPixels() or setPixels() is called, and will draw nothing. This Operation     * cannot be reversed, so it should only be called if you are sure there are no     * further uses for the bitmap. This is an advanced call, and normally need     * not be called, since the normal GC PRocess will free up this memory when     * there are no more references to this bitmap.     */    public void recycle() {        if (!mRecycled && mNativePtr != 0) {            if (nativeRecycle(mNativePtr)) {                // return value indicates whether native pixel object was actually recycled.                // false indicates that it is still in use at the native level and these                // objects should not be collected now. They will be collected later when the                // Bitmap itself is collected.                mBuffer = null;                mNinePatchChunk = null;            }            mRecycled = true;        }    }
简单总结下：
1. recycle()方法释放该Bitmap对应的 native object，清除了该bitmap的pixel data的饮用，但是没有立即释放 pixel data。
2. 一般情况下不需要主动调用，gc会处理bitmap的回收。如过需要立即释放bitmap对应的 native object，可以调用，但是要慎重。否则会出问题：
    java.lang.RuntimeException: Canvas: trying to use a recycled bitmap android.graphics.Bitmap
以上是2.3以后的版本。2.3以前的需要主动调用recycle(). 因为2.3及以前的版本中，bitmap的数据是放在栈中而不是堆中。（gc回收主要回收堆中的内存）