BitmapFactory.Options.inSampleSize
设置恰当的inSampleSize可以使BitmapFactory分配更少的空间以消除该错误。inSampleSize的具体含义请参考SDK文档。例如：
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。
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
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
// 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。
获取缩略图关键代码：
byte[] imageByte=getImageFromURL(urlPath[i].trim());
//以下是把图片转化为缩略图再加载
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true; //首先设置.inJustDecodeBounds为true
Bitmap bitmap=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length, options); //这时获取到的bitmap是null的，尚未调用系统内存资源
options.inJustDecodeBounds = false; 得到图片有宽和高的options对象后，设置.inJustDecodeBounds为false。
int be = (int)(options.outHeight / (float)200);
if (be <= 0) be = 1;
options.inSampleSize = be; //计算得到图片缩小倍数
bitmaps[i]=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length,options); //获取真正的图片对象(缩略图)
/**
* 根据图片网络地址获取图片的byte[]类型数据
* @param urlPath 图片网络地址
* @return 图片数据
*/
public byte[] getImageFromURL(String urlPath){
byte[] data=null;
InputStream is=null;
HttpURLConnection conn=null;
try {
URL url=new URL(urlPath);
conn=(HttpURLConnection) url.openConnection();
conn.setDoInput(true);
//conn.setDoOutput(true);
conn.setRequestMethod("GET" );
conn.setConnectTimeout(6000 );
is=conn.getInputStream();
if(conn.getResponseCode()==200 ){
data=readInputStream(is);
}
else System.out.println("发生异常！" );
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally{
conn.disconnect();
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return data;
}
/**
* 读取InputStream数据，转为byte[]数据类型
* @param is InputStream数据
* @return 返回byte[]数据
*/
public byte[] readInputStream(InputStream is) {
ByteArrayOutputStream baos=new ByteArrayOutputStream();
byte[] buffer=new byte[1024 ];
int length=-1 ;
try {
while((length=is.read(buffer))!=-1 ){
baos.write(buffer, 0 , length);
}
baos.flush();
} catch (IOException e) {
e.printStackTrace();
}
byte[] data=baos.toByteArray();
try {
is.close();
baos.close();
} catch (IOException e) {
e.printStackTrace();
}
return data;
}
/**
* 根据网络图片地址集批量获取网络图片
* @param urlPath 网络图片地址数组
* @return 返回Bitmap数据类型的数组
*/
public Bitmap[] getBitmapArray(String[] urlPath){
int length=urlPath.length;
if(urlPath==null||length<1 ){
return null;
}
else{
Bitmap[] bitmaps=new Bitmap[length];
for (int i = 0 ; i < length; i++) {
byte[] imageByte=getImageFromURL(urlPath[i].trim());
//以下是把图片转化为缩略图再加载
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
Bitmap bitmap=BitmapFactory.decodeByteArray(imageByte, 0 , imageByte.length, options);
options.inJustDecodeBounds = false;
int be = (int)(options.outHeight / (float)200 );
if (be <= 0 ) be = 1 ;
options.inSampleSize = be;
bitmaps[i]=BitmapFactory.decodeByteArray(imageByte, 0 , imageByte.length,options);
}
return bitmaps;
}
}