How rebuild only one module in project Android Studio

int occupy 4 bytes (32 bits) in memory

int in Java example of using Integer and Array of Integer and Iteger to String

        // get max end min values of int in Java example 4 bytes (32 bits) PC architecture
	System.out.println(Integer.MAX_VALUE); // 2147483647
	System.out.println(Integer.MIN_VALUE); // -2147483648


// members variable
private int mProgress = 10;

//integer to string java
int myInteger = 8;
String myString = Integer.toString(myInteger);

// a final variable can only be initialized once
static final int NUM_PARTICLES = 15;

 for (int i = 0; i < NUM_PARTICLES ; i++) { 
// do something
}

// int as return value of function
public int getCount() {
return 5;
}

// int as a parametr of function
public float getFloatFromInt(int i) {
float fRet = (float) i;
 return fRet;
}

//array of int
int[] anArray;              // declares an array of integers
          anArray = new int[2];      // allocates memory for 2 integers
          anArray[0] = 100; // initialize first element
          anArray[1] = 200; // initialize second element

for (int i = 0; i < anArray.length; i++) {
// print out values from anArray
System.out.println("Index: " + i);
System.out.println("Value: " + anArray[i]); 
}

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.

Get display, screen resolution - dimension Android phone development example source code.

 Display display = getWindowManager().getDefaultDisplay();
int nWidth = display.getWidth();
int nHeight = display.getHeight();

          DisplayMetrics metrics = new DisplayMetrics();
            getWindowManager().getDefaultDisplay().getMetrics(metrics);
            //get density per inch for example: 120 , 160 , 240
            mXDpi = metrics.xdpi; // 160 The exact physical pixels per inch of the screen in the X dimension. 
            mYDpi = metrics.ydpi;

// density
int nDensity = metrics.densityDpi; // 160 screen density expressed as dots-per-inch

          float  mMetersToPixelsX = mXDpi / 0.0254f; // 1 inch == 0.0254 metre
          float  mMetersToPixelsY = mYDpi / 0.0254f;
          
// Resolution
// The total number of physical pixels on a screen.
int wPix = metrics.widthPixels; // 320 The absolute width of the display in pixels.
int hPix = metrics.heightPixels; // 480 The absolute height of the display in pixels.
int nWidthDisplay = (wPix < hPix)? wPix : hPix;

float nWidthScreenInInch = wPix / mXDpi; //320 / 160 == 2.0 in inch.
float nHeightScreenInInch = hPix / mYDpi; //480 / 160 == 3.0 in inch.

// for example:
// density 120 per inch
//width 320 pix / 120 dpi == width 2.66 inch
//height 480 pix / 120 dpi == height 4.0 inch 

// density 240 per inch
//width 320 pix / 240 dpi == width 1.33 inch
//height 480 pix / 240 dpi == height 2.0 inch 

Example:
HTC Desire HD
11 (4.3) Diagonal cm (in)
480×800 Resolution
85 (217) ppcm (PPI - Pixels per inch)

480 / 217 = 2.21 inch
800 / 217 = 3.69 inch
Math.sqrt( 2.21*2.21 + 3.69 * 3.69) = 4.3 inch - diagonal

//en.wikipedia.org/wiki/Pixels_per_inch
//en.wikipedia.org/wiki/Dots_per_inch

Typical screen widths:

320dp: a typical phone screen (240x320 ldpi, 320x480 mdpi, 480x800 hdpi, etc).
480dp: a tweener tablet like the Streak (480x800 mdpi).
600dp: a 7” tablet (600x1024 mdpi).
720dp: a 10” tablet (720x1280 mdpi, 800x1280 mdpi, etc).


Emulator skins in the Android SDK
//developer.android.com/guide/practices/screens_support.html

	Low density (120), ldpi	Medium density (160), mdpi	High density (240), hdpi	Extra high density (320), xhdpi
Small screen	QVGA (240x320)		480x640
Normal screen	WQVGA400 (240x400) WQVGA432 (240x432)	HVGA (320x480)	WVGA800 (480x800) WVGA854 (480x854) 600x1024	640x960
Large screen	WVGA800** (480x800) WVGA854** (480x854)	WVGA800* (480x800) WVGA854* (480x854) 600x1024
Extra Large screen	1024x600	WXGA (1280x800)† 1024x768 1280x768	1536x1152 1920x1152 1920x1200	2048x1536 2560x1536 2560x1600
* To emulate this configuration, specify a custom density of 160 when creating an AVD that uses a WVGA800 or WVGA854 skin. ** To emulate this configuration, specify a custom density of 120 when creating an AVD that uses a WVGA800 or WVGA854 skin. † This skin is available with the Android 3.0 platform

MainActivity.java

        ProgressBar mProgressBarScore;
      // onCreate
	mProgressBarScore = (ProgressBar)findViewById(R.id.progressBarScore);
	Resources res = getResources();
	mProgressBarScore.setProgressDrawable(res.getDrawable( R.drawable.my_progress));

res/layout/main.xml

       <ProgressBar
            android:id="@+id/progressBarScore"
            style="?android:attr/progressBarStyleHorizontal"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" android:max="100"/>

res/drawable/my_progress.xml

    

        

        

                        android:startColor="#FF001A"

                android:centerColor="#ff5a5d5a"

                android:centerY="0.75"

                android:endColor="#FF001A"

                android:angle="270"

        />

    







    

        

            

                                android:startColor="#80ffd300"

                    android:centerColor="#80ffb600"

                    android:centerY="0.75"

                    android:endColor="#a0ffcb00"

                    android:angle="270"

            />

        

    



    android:id="@android:id/progress"

>

    

        

            

                            android:radius="10dip" />

                            android:startColor="#00ff00"

                android:centerColor="#80ffb600"

                android:centerY="0.75"

                android:endColor="#339900"

                android:angle="270" />

        

    

If you using Context as parameter of function try this solution:

public class MyActivity extends Activity {
// bla bla bla .......
//error 
myFc( getapplicationcontext());
// OK
myFc(MyActivity.this);