刚开始会出现加载不出控件的情况，获取width和height可能为0，所以放在onWindowFocusChanged方法中
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
// ImageView 的实际大小
int width = img.getWidth();
int height = img.getHeight();
Log.e(TAG, "initView: " + "width:" + width + ",height:" + height);
// 不二次采样bitmap大小
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.bb);
Log.e(TAG, "init: " +"不二次采样bitmap大小: "+bitmap.getAllocationByteCount() );
// 设置为true,加载图片时不会获取到bitmap对象,但是可以拿到图片的宽高
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.drawable.bb, options);
// 获取图像的宽高值
int outWidth = options.outWidth;
int outHeight = options.outHeight;
Log.e(TAG, "init: " + "outWidth: "+outWidth+",outHeight:"+outHeight);
// 计算宽度比和高度比
float widthRatio = outWidth * 1.0f / width;
float heightRatio = outHeight * 1.0f / height;
Log.e(TAG, "init: " + "widthRatio: "+widthRatio+",heightRatio:"+heightRatio);
// 计算采样率
float max = Math.max(widthRatio, heightRatio);
int inSampleSize = (int) Math.ceil(max);
Log.e(TAG, "init: " + "inSampleSize: "+inSampleSize);
// 设置通过采样率更改压缩图片，加载图片显示
options.inJustDecodeBounds=false;
options.inSampleSize = inSampleSize;
// 二次采样bitmap大小
Bitmap bitmap1 = BitmapFactory.decodeResource(getResources(), R.drawable.bb, options);
// 显示压缩后的图片
img.setImageBitmap(bitmap1);
}
