R.string to string R.array to array Android

android:gravity="left|center_vertical" or android:gravity="right|center_vertical"

               
<Button
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="left|center_vertical"
                    android:paddingLeft="20dp"
                    android:text="My Button"
                     />

Difference between "@+id/” and "@id/” in Android
android:id="@+id/xxx" unique identifier of view
@id/ a reference to the unique identifier

 <TextView
        android:id="@+id/first_element_id"
        .........
 />
    <TextView
        android:id="@+id/second_element_id"
        android:layout_below="@id/first_element_id"
        ..........
 />

Draw the trajectory of shot.

public class MainActivity extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new SampleView(this));
	}

	private static class SampleView extends View {

		// CONSTRUCTOR
		public SampleView(Context context) {
			super(context);
			setFocusable(true);

		}
	       private static void makePath(Path p) {
	            p.moveTo(10, 0);
	            p.cubicTo(100, -50, 200, 150, 300, 0);
	        }
		@Override
		protected void onDraw(Canvas canvas) {

			canvas.drawColor(Color.CYAN);
			Paint p = new Paint();
			// smooths
			p.setAntiAlias(true);
			p.setColor(Color.RED);
			p.setStyle(Paint.Style.STROKE); 
			p.setStrokeWidth(5);
			// opacity
			//p.setAlpha(0x80);
 
			p.setColor(Color.BLACK);
			Path mPath = new Path();
            makePath(mPath);
			canvas.drawPath(mPath, p); //(rectF, 90, 45, true, p);
		}

	}
}

How get Android SDK location - PATH on PC from Eclipse tutorial.

1. Open dialog from menu Window -> AVD and SDK manager


2. In dialog select Available packages


3. On top of dialog will displayed similar path: SKD Location: C:\PROGRA~1\Android\android-sdk-windows\

Eclipse make own color of toolbars, windows, status bar etc.
https://github.com/jeeeyul/eclipse-themes/wiki/Alternative-Install