layout id cannot be resolved or is not a field

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added: Lcz/okhelp/MyMathClass;

First try this solution!!!!!
Select your project in project tree and go to the Eclipse menu Project » Clean » Clean projects selected below » select your project and click OK.

If you create *.apk package with proguard sometimes you must back up the project, delete project, and create new project if you are unable to create *.apk file.

Check your AndroidManifest.xml if all Activity is correctly inserted. If you add a library project to Main project you have to insert Activity from library to Main project AndroidManifest.xml


Problem with the library.
I deleted library project from project tree and again put the _library project into the main project. This problem was resolved.
1.)Go to Project » Properties » Java Build Path » Libraries and remove (your projects) click OK.
2.)Go to Project » Clean » Clean projects selected below » select your project and click OK.
3.)Add again your LIBRARY project to your MAIN project Project » Properties » Java Build Path » Libraries.
See image below.

Problem with a *.apk file
If you create signed *.apk, you have to delete previous *.apk from your PC folder.

"id cannot be resolved or is not a field” error
If you copy project to workspace or some code from other project you can get this error.

Try remove or add import your R file:

import com.example.app.R

Check xml files.
Clean project by menu Project-Clean

Maybe you have to create new project end copy old source files to new project folders.

Very dark picture, in photo editor black remains black


Very bright picture, in photo editor white will white


Dark picture but the chart is not in black color area - dark shades can be lighten in graphics editor

Table of usability of mobile phones with Android – February 2012 - (application Sky Map)

1	Samsung Galaxy S2	6.3%
2	HTC Desire HD	3.5%
3	HTC Evo 4G	3.4%
4	Samsung Galaxy Ace	2.1%
5	Samsung Galaxy S (SCH-I500)	2.1%
6	Samsung Galaxy S (GT-I9000)	2.1%
7	HTC Incredible 2	2.0%
8	Motorola Droid X	1.9%
9	Motorola Droid RAZR	1.9%
10	HTC Sensation 4G	1.7%

TypeFace, setTypeface, font, font family, array of String, Button create dynamically

@Override
protected void onStart() {
LinearLayout.LayoutParams p = new LinearLayout.LayoutParams(
  48,
  55
);	
Typeface typeFace = Typeface.MONOSPACE;	
String [] ar = {"A","B","C","D","E","F","G","H","J","K"};
for (int i = 0; i < ar.length; i++) {
Button buttonView = new Button(this);
buttonView.setText(Html.fromHtml("<b>"+ar[i]+"</b>"));
buttonView.setTextColor(Color.BLUE);
buttonView.setTextSize(27.f);
buttonView.setTypeface(typeFace,Typeface.BOLD);
buttonView.setOnClickListener(mThisButtonListener);
if(i%2==0)
	mLayoutButtons.addView(buttonView, p);
else
	mLayoutButtonsNextRow.addView(buttonView, p);
	
_listOfButtons.add(buttonView);
}

	super.onStart();
}

//////// xml file
<TextView
    android:id="@+id/text01"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="20dp"
    android:fontFamily="Arial"
 />