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BitmapFactory.decodeFile(imageFile);
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用BitmapFactory解碼一張圖片時，有時會遇到該錯誤。這往往是由於圖片過大造成的。要想正常使用，則需要分配更少的內存空間來存儲。
BitmapFactory.Options.inSampleSize
設置恰當的inSampleSize可以使BitmapFactory分配更少的空間以消除該錯誤。inSampleSize的具體含義請參考SDK文檔。例如：
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BitmapFactory.Options opts =
new
BitmapFactory.Options();
opts.inSampleSize =
4
;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
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如何設置恰當的inSampleSize
設置恰當的inSampleSize是解決該問題的關鍵之一。BitmapFactory.Options提供了另一個成員inJustDecodeBounds。
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BitmapFactory.Options opts =
new
BitmapFactory.Options();
opts.inJustDecodeBounds =
true
;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
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設置inJustDecodeBounds為true后，decodeFile並不分配空間，但可計算出原始圖片的長度和寬度，即opts.width和opts.height。有了這兩個參數，再通過一定的算法，即可得到一個恰當的inSampleSize。
查看Android源碼，Android提供了一種動態計算的方法。
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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;
}
}
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使用該算法，就可動態計算出圖片的inSampleSize。
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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) {
}
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另外，可以通過Bitmap.recycle()方法來釋放位圖所占的空間，當然前提是位圖沒有被使用。
獲取縮略圖關鍵代碼
byte[] imageByte=getImageFromURL(urlPath[i].trim());
//以下是把圖片轉化為縮略圖再加載
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true; //首先設置.inJustDecodeBounds為true
Bitmap bitmap=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length, options); //這時獲取到的bitmap是null的，尚未調用系統內存資源
options.inJustDecodeBounds = false; 得到圖片有寬和高的options對象后，設置.inJustDecodeBounds為false。
int be = (int)(options.outHeight / (float)200);
if (be <= 0) be = 1;
options.inSampleSize = be; //計算得到圖片縮小倍數
bitmaps[i]=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length,options); //獲取真正的圖片對象（縮略圖）
/**
* 根據圖片網絡地址獲取圖片的byte[]類型數據
* @param urlPath 圖片網絡地址
* @return 圖片數據
*/
- 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("發生異常！" );
- } catch (MalformedURLException e) {
- e.printStackTrace();
- } catch (IOException e) {
- e.printStackTrace();
- }
- finally{
- conn.disconnect();
- try {
- is.close();
- } catch (IOException e) {
- e.printStackTrace();
- }
- }
- return data;
- }
- /**
- * 讀取InputStream數據，轉為byte[]數據類型
- * @param is InputStream數據
- * @return 返回byte[]數據
- */
- 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;
- }
- /**
- * 根據網絡圖片地址集批量獲取網絡圖片
- * @param urlPath 網絡圖片地址數組
- * @return 返回Bitmap數據類型的數組
- */
- 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());
- //以下是把圖片轉化為縮略圖再加載
- 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;
- }
- }
以