ViewPager加载了五张大图，每张图都是2M，左右翻页会很卡很卡，该怎么解决
是本地图片吗？可以先展示缩略图，再展示原始图。加载都在子线程中进行。
读取缩略图的方法：
/**
* 通过限制加载图片的宽度和高度，限制不加载超大图片
*
* @param dst 图片文件
* @param width 宽度
* @param height 高度
*/
public static Bitmap getBitmapFromFile(File dst, int width, int height) {
if (null != dst && dst.exists()) {
BitmapFactory.Options opts = null;
if (width > 0 && height > 0) {
opts = new BitmapFactory.Options();
//设置inJustDecodeBounds为true后，decodeFile并不分配空间，此时计算原始图片的长度和宽度
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(dst.getPath(), opts);
// 计算图片缩放比例
final int minSideLength = Math.min(width, height);
opts.inSampleSize = computeSampleSize(opts, minSideLength, width * height);
//这里一定要将其设置回false，因为之前我们将其设置成了true
opts.inJustDecodeBounds = false;
opts.inInputShareable = true;
opts.inPurgeable = true;
}
try {
return BitmapFactory.decodeFile(dst.getPath(), opts);
} catch (OutOfMemoryError e) {
e.printStackTrace();
}
}
return null;
}
private 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;
}
}