解决java.lang.OutOfMemoryError: bitmap size exceeds VM budget模式一

解决java.lang.OutOfMemoryError: bitmap size exceeds VM budget方式一

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：

?

BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = 4;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);

?

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。

?

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。

?

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。

?

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。