完美解决java.lang.OutOfMemoryError: bitmap size exceeds VM budget

完美解决java.lang.OutOfMemoryError: bitmap size exceeds VM budget（转自http://blog.csdn.net/yangxyjd/article/details/6932989）

当图片过大，或图片数量较多时使用BitmapFactory解码图片会出java.lang.OutOfMemoryError: bitmap size exceeds VM budget，要想正常使用则需分配更少的内存，具体的解决办法是修改采样值BitmapFactory.Options.inSampleSize，例如：

[java] view
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BitmapFactory.Options opts = new BitmapFactory.Options();

opts.inSampleSize = 4;

Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);

如何设置恰当的inSampleSize
设置恰当的inSampleSize是解决该问题的关键之一。BitmapFactory.Options提供了另一个成员inJustDecodeBounds。

[java] view
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BitmapFactory.Options opts = new BitmapFactory.Options();

opts.inJustDecodeBounds = true;

Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);

设置inJustDecodeBounds为true后，decodeFile并不分配空间，但可计算出原始图片的长度和宽度，即opts.width和opts.height。有了这两个参数，再通过一定的算法，即可得到一个恰当的inSampleSize。

查看Android源码，Android提供了一种动态计算的方法。

[java] view
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public static int computeSampleSize(BitmapFactory.Options options,

int minSideLength, int maxNumOfPixels) {

int initialSize = computeInitialSampleSize(options, minSideLength,maxNumOfPixels);

int roundedSize;

if (initialSize <= 8 ) {

roundedSize = 1;

while (roundedSize < initialSize) {

roundedSize <<= 1;

}

} else {

roundedSize = (initialSize + 7) / 8 * 8;

}

return roundedSize;

}

private static int computeInitialSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) {

double w = options.outWidth;

double h = options.outHeight;

int lowerBound = (maxNumOfPixels == -1) ? 1 :

(int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels));

int upperBound = (minSideLength == -1) ? 128 :

(int) Math.min(Math.floor(w / minSideLength),

Math.floor(h / minSideLength));

if (upperBound < lowerBound) {

// return the larger one when there is no overlapping zone.

return lowerBound;

}

if ((maxNumOfPixels == -1) &&

(minSideLength == -1)) {

return 1;

} else if (minSideLength == -1) {

return lowerBound;

} else {

return upperBound;

}

}

使用该算法，就可动态计算出图片的inSampleSize。

[java] view
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BitmapFactory.Options opts = new BitmapFactory.Options();

opts.inJustDecodeBounds = true;

BitmapFactory.decodeFile(imageFile, opts);

opts.inSampleSize = computeSampleSize(opts, -1, 128*128);

opts.inJustDecodeBounds = false;

try {

Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts);

imageView.setImageBitmap(bmp);

} catch (OutOfMemoryError err) {

}

另外，可以通过Bitmap.recycle()方法来释放位图所占的空间，当然前提是位图没有被使用。