为何AndroidStudio的ImageView控件的background的drawable属性没有了 Android stdio怎么没有不同分辨率的drawable文件
为何AndroidStudio的ImageView控件的background的drawable属性没有了
在imageview里面你想加入图片你改用android：src加入图片你用background表示的是这个imageview的背景。你设置背景是可以的，当你设置了imageview的宽和高，设置了背景，而你通过android：src加入的图片没有你设置的imageview的宽或高时，你就会在图片边沿看到你设置的背景，不过大部份已被图片掩盖。
Android stdio怎么没有不同分辨率的drawable文件
有的，只是android studio已经隐藏掉了,因为android studio自动将同名的文件集合在一起,可以切换一个视图来显示,点击最上面那个Android切换成Project即可显示出来了。
关于android studio mipmap 和drawable的区别
studio mipmap 和drawable的区别！最近使用studio 发现drawle-hdpi 都没有了换成了mipmap-hdpi，这两个目录有什么区别呢?
使用上没有任何区别,你把它当drawable用就好了。
但是用mipmap系统会在缩放上提供一定的性能优化。
官方介绍：
Mipmapping for drawables
Using a mipmap as the source for your bitmap or drawable is a simple way to
provide a quality image and various image scales, which can be particularly
useful if you expect your image to be scaled during an animation.
Android 4.2 (API level 17) added support for mipmaps in the Bitmap
class—Android swaps the mip images in your Bitmap when youve supplied a mipmap
source and have enabled setHasMipMap(). Now in Android 4.3, you can enable
mipmaps for a BitmapDrawable object as well, by providing a mipmap asset and
setting the android:mipMap attribute in a bitmap resource file or by calling
hasMipMap().
应用场景：
If you know that you are going to draw this bitmap at less than 50% of its
original size, you may be able to obtain a higher quality by turning this
property on. Note that if the renderer respects this hint it might have to
allocate extra memory to hold the mipmap levels for this bitmap.
一个应用实例：
Nexus 6
Screen
The Nexus 6 boasts an impressive 5.96” Quad HD screen display at a
resolution of 2560 x 1440 (493 ppi). This translates to ~ 730 x 410 dp (density
independent pixels).
Check your assets
It has a quantized density of 560 dpi, which falls in between the xxhdpi
and xxxhdpi primary density buckets. For the Nexus 6, the platform will scale
down xxxhdpi assets, but if those aren’t available, then it will scale up xxhdpi
assets.
Provide at least an xxxhdpi app icon because devices can display large app
icons on the launcher. It’s best practice to place your app icons in mipmap-
folders (not the drawable- folders) because they are used at resolutions
different from the device’s current density. For example, an xxxhdpi app icon
can be used on the launcher for an xxhdpi device.
p icon used on Nexus 6 device launcher
res/
mipmap-mdpi/
ic_launcher.png
mipmap-hdpi/
ic_launcher.png
mipmap-xhdpi/
ic_launcher.png
mipmap-xxhdpi/
ic_launcher.png
mipmap-xxxhdpi/
ic_launcher.png # App icon used on Nexus 6 device launcher
Choosing to add xxxhdpi versions for the rest of your assets will provide a
sharper visual experience on the Nexus 6, but does increase apk size, so you
should make an appropriate decision for your app.
res/
drawable-mdpi/
ic_sunny.png
drawable-hdpi/
ic_sunny.png
drawable-xhdpi/
ic_sunny.png
drawable-xxhdpi/ # Fall back to these if xxxhdpi versions aren’t
available
ic_sunny.png
drawable-xxxhdpi/ # Higher resolution assets for Nexus 6
ic_sunny.png
总结
这个实例总结一下是这样：
Nexus 6 有 493 ppi，它刚好在
xxhdpi和xxxhdpi之间，所以显示的时候需要对xxxhdpi的资源进行缩小，如果你用了mipmap-xxxhdpi,那么这里会对sclae有一个优化，性能更好，占用内存更少。所以现在官方推荐使用mipmap：
It’s best practice to place your app icons in mipmap- folders (not the
drawable- folders) because they are used at resolutions different from the
device’s current density.
android getdrawable用什么代替
之前代码中获取Drawable都是使用如下方法：
Drawable TopDrawableOne = getResources().getDrawable(R.drawable.icon_test)
但是此方法过时，不推荐使用，那么肯定是有其他替代方法的，经过查找，很多网友都是推荐使用
Drawable getDrawable(int id, Resources.Theme theme), 第二个参数@theme可以为空值.或Context.getDrawable(int)
但是感觉此方法不是很好用就在此查找有没有其他好用的方法，最后找到
Drawable TopDrawableOne = ContextCompat.getDrawable(context,R.drawable.icon_test)
这种方式，看着舒服，也是谷歌推荐使用的。