Android – What does onPrepareOptionsMenu do

androidmenuoptionmenu

I want to make Option Menu for Android, I have visit this site. In their script, I found onPrepareOptionsMenu, I try to compile and run using Android 2.3.3 compiler with and without onPrepareOptionsMenu, both works, but I didn't see any difference.

public boolean onCreateOptionsMenu(Menu menu){
    //code here
}
    
public boolean onOptionsItemSelected(MenuItem item){
    //code here
}
    
public boolean onPrepareOptionsMenu(Menu menu){
    //code here
}

What is actually onPrepareOptionsMenu method do? Is that method important? Could I just delete the method?

Addition

Oh, I also hear about Action Bar in Android 3.0, it says that Action Bar is the alternative way for make Option Menu, and it using onPrepareOptionsMenu. Is that right?

Thank you…

Best Answer

Take a look in the API:

Prepare the Screen's standard options menu to be displayed. This is called right before the menu is shown, every time it is shown. You can use this method to efficiently enable/disable items or otherwise dynamically modify the contents.

Related Solutions

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 – ‘Context’ on Android

Putting it simply:

As the name suggests, it's the context of the current state of the application/object. It lets newly-created objects understand what has been going on. Typically you call it to get information regarding another part of your program (activity and package/application).

You can get the context by invoking getApplicationContext(), getContext(), getBaseContext() or this (when in a class that extends from Context, such as the Application, Activity, Service and IntentService classes).

Typical uses of context:

Creating new objects: Creating new views, adapters, listeners:

 TextView tv = new TextView(getContext());
 ListAdapter adapter = new SimpleCursorAdapter(getApplicationContext(), ...);

Accessing standard common resources: Services like LAYOUT_INFLATER_SERVICE, SharedPreferences:

 context.getSystemService(LAYOUT_INFLATER_SERVICE)
 getApplicationContext().getSharedPreferences(*name*, *mode*);

Accessing components implicitly: Regarding content providers, broadcasts, intent
```
 getApplicationContext().getContentResolver().query(uri, ...);
```

Best Answer

Related Solutions

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

Android – ‘Context’ on Android

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