Usefull function for android

1) findViewById(R.id.<type control name>);

Example   

Button myButton = (Button) findViewById(R.id.my_button);

noKids = (EditText) findViewById(R.id.xetKids);

 This function use for create object of android control

R is reserve class R is a class that contains ONLY public constants.

 (public static final). It is a generated class (by Android Plugin in Eclipse)

 that reflects the various values you defined in the res file.

 For instance, you should have something like: android:id="@+id/about_button" 

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2)Double.parseDouble(<string>);

Example

etKids = Double.parseDouble(noKids.getText().toString()); 

This function convert string to Double data type for mathematics calculation.

3)Toast()

Toast.makeText(context, text, duration).show();

Example

Toast.makeText(context,"Message saved as draft", duration).show(); 

This method is used to display some message to user screen.

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