1.重写View的onMeasure方法(参考博客：http://www.jianshu.com/p/c9424615e99d)
核心代码
protectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec){
Drawable d = getDrawable();if(d!=null){// ceil not round - avoid thin vertical gaps along the left/right edgesintwidth = MeasureSpec.getSize(widthMeasureSpec);//高度根据使得图片的宽度充满屏幕计算而得intheight = (int) Math.ceil((float) width * (float) d.getIntrinsicHeight() / (float) d.getIntrinsicWidth());
setMeasuredDimension(width, height);
}else{super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
2.设置ImageView的属性：
//宽度填满屏幕
android:layout_width=”match_parent”
android:scaleType=”fitXY”
android:layout_height=”wrap_content”
//保持比例，一定要设置
android:adjustViewBounds=”true”
android:src = "@drawable/icon1"
3.将ImageVIew的属性src改成background