android bitmap集合怎么释放,直接clear,可以吗
发布网友
发布时间：2022-05-14 18:08
共1个回答
热心网友
时间：2023-10-19 10:50
我们知道，用完一个Bitmap后，需要马上recycle()来保证尽快释放期资源。首先，我们来看看recycle()这个函数的定义（Bitmap.java）：
[java] view plaincopy
public void recycle() {
if (!mRecycled) {
if (nativeRecycle(mNativeBitmap)) {
// 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;
}
}
代码很简单，主要调用这个函数：nativeRecycle(mNativeBitmap)去释放。这里是JNI方式去调用了c写的方法！其实，你看看一下Bitmap这个类，就知道了，其实Bitmap的实现主要都是用C写的，为了保证效率这样选择是必然的！ 这不是我们讨论的重点。我们来看看google给这个函数的一段说明：
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/**
* 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.
*/
通过这段说明我们知道调用这个函数其实只是会free一些相关的资源、对于其t图片像素数据并没有同步释放，而且这个方法通常也不是必要的，就是说：不是一定要调用这个函数这个Bitmap才会被GC回收。那么问题就来了：刚才说了，那图片像素这类数据是如何释放的呢？最重要的是bitmap处理的核心代码不是JAVA写的。
这个时候finalize()就登场了。我们先看看里面定义的一个私有变量private final BitmapFinalizer mFinalizer; BitmapFinalizer 是Bitmap的内部类：
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private static class BitmapFinalizer {
private final int mNativeBitmap;
BitmapFinalizer(int nativeBitmap) {
mNativeBitmap = nativeBitmap;
}
@Override
public void finalize() {
try {
super.finalize();
} catch (Throwable t) {
// Ignore
} finally {
nativeDestructor(mNativeBitmap);
}
}
}
这里很好的利用object的finalize()这个回调函数，安卓博客http://www.bafenbaosoft.com 这样就来保证一个Bitmap对象被释放的时候能够回调void nativeDestructor(int nativeBitmap);这个函数来释放C里面申请的资源！
