Android – What’s the difference between commit() and apply() in SharedPreferences

androidsharedpreferences

I am using SharedPreferences in my android app. I am using both commit() and apply() method from shared preference. When I use AVD 2.3 it shows no error, but when I run the code in AVD 2.1, apply() method shows error.

So what's the difference between these two? And by using only commit() can I store the preference value without any problem?

Best Answer

apply() was added in 2.3, it commits without returning a boolean indicating success or failure.

commit() returns true if the save works, false otherwise.

apply() was added as the Android dev team noticed that almost no one took notice of the return value, so apply is faster as it is asynchronous.

http://developer.android.com/reference/android/content/SharedPreferences.Editor.html#apply()

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Android – the difference between “px”, “dip”, “dp” and “sp”

From the Android Developer Documentation:

px
> Pixels - corresponds to actual pixels on the screen.
in
> Inches - based on the physical size of the screen.
> 1 Inch = 2.54 centimeters
mm
> Millimeters - based on the physical size of the screen.
pt
> Points - 1/72 of an inch based on the physical size of the screen.
dp or dip
> Density-independent Pixels - an abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi screen, so one dp is one pixel on a 160 dpi screen. The ratio of dp-to-pixel will change with the screen density, but not necessarily in direct proportion. Note: The compiler accepts both "dip" and "dp", though "dp" is more consistent with "sp".
sp
> Scaleable Pixels OR scale-independent pixels - this is like the dp unit, but it is also scaled by the user's font size preference. It is recommended you use this unit when specifying font sizes, so they will be adjusted for both the screen density and the user's preference. Note, the Android documentation is inconsistent on what sp actually stands for, one doc says "scale-independent pixels", the other says "scaleable pixels".

From Understanding Density Independence In Android:

Density Bucket	Screen Density	Physical Size	Pixel Size
ldpi	120 dpi	0.5 x 0.5 in	0.5 in * 120 dpi = 60x60 px
mdpi	160 dpi	0.5 x 0.5 in	0.5 in * 160 dpi = 80x80 px
hdpi	240 dpi	0.5 x 0.5 in	0.5 in * 240 dpi = 120x120 px
xhdpi	320 dpi	0.5 x 0.5 in	0.5 in * 320 dpi = 160x160 px
xxhdpi	480 dpi	0.5 x 0.5 in	0.5 in * 480 dpi = 240x240 px
xxxhdpi	640 dpi	0.5 x 0.5 in	0.5 in * 640 dpi = 320x320 px

Unit	Description	Units Per Physical Inch	Density Independent?	Same Physical Size On Every Screen?
px	Pixels	Varies	No	No
in	Inches	1	Yes	Yes
mm	Millimeters	25.4	Yes	Yes
pt	Points	72	Yes	Yes
dp	Density Independent Pixels	~160	Yes	No
sp	Scale Independent Pixels	~160	Yes	No

More info can be also be found in the Google Design Documentation.

Android – the difference between gravity and layout_gravity in Android

Their names should help you:

android:gravity sets the gravity of the contents (i.e. its subviews) of the View it's used on.
android:layout_gravity sets the gravity of the View or Layout relative to its parent.

And an example is here.

Best Answer

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