Screen Android Landscape Portrait programmatically

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"
        ..........
 />

The Android WebView changing the height according to text size.
If you need to change the height to a minimum try this source:

//public void loadDataWithBaseURL (String baseUrl, String data, String mimeType, String encoding, String historyUrl) 
WebView _webView; // findById(.....
String entryContent = "";
 _webView.loadDataWithBaseURL(
	"blabol",//  javascript i styly
	entryContent, null,
	"utf-8", null
);

If Android emulator freezes at startup, try create new virtual device with smaller memory and cpu usage, or select older version of Android, or buy new pc with higher performance.

1. open AVD MANAGER


2. press Create Virtual Device


3. select Device with small memory usage (e.g. 480x800 of resolution) - Next


4. check - Show downloadable ....


5. Download - lower version of system Android, select, press - Next


6. check data, Show Advanced Settings, check Use host... and press Finish

If you have trouble with compilation of new project after you make a update of android development tools you can go back to old version of the tools.

• 
  
  
  
  • Open Help > About Eclipse... use the menu > About...
  
  
  • Click the "Installation Details" button.
  
  
  • Select the "Installation History" tab.
  
  
  • Select one of the previous configurations.
  
  
  • Click the "Revert" button at the bottom.
  
  
  
  

Java double is 64 bit double precision type used when fractional
precision calculation is required.

Java double je datový typ (reálné číslo) o velikosti 64 bitů. Používá se například pro přesný výsledek po dělení za desetinnou tečkou. Pokud nepotřebuje tak veliké číslo použijte raději typ float, šetříte tím paměť mobilního telefonu.

		// declaration and assignment of value  type double
		double x = 18.41785;
		//print formated  value
		System.out.printf("The value of x is %.3f%n", x); // 18.418
                
                // declaring more variables in single statement
                double d1 = 12.4, d2 = 564.5, d3 = 14.589;

		// double range of value
		System.out.println(Double.MIN_VALUE); // 4.9E-324
		System.out.println(Double.MAX_VALUE); // 1.7976931348623157E308

		// is NaN  Not-a-Number
		double f = (double) Math.sqrt(-15);
		boolean bNaN = Double.isNaN(f);
		System.out.print(bNaN); // true
		
                // check if a string is a valid number in Java example
                // convert string to double Java example
		String sD = "12.8";
		double dParse = Double.parseDouble(sD);

	       // convert strings to numbers
	      String sDl = "15.48";
	      double dFromString = (Double.valueOf(sDl)).doubleValue();

// format double, float or long value to string
	DecimalFormat formatter = new DecimalFormat(".##");
	String s = formatter.format(-.5678);             // -0.57
// .###  -0.568
// .#### -0.5678
// .000000  -.567800

// -123.456
// .##  -123.46
// #.##  -123.46

// #E0  -.1E3
// ##E0  -1.2E2
//###E0  -123E0

// double to string in Java example code
Double dObj = new Double(68.5);
String str = dObj.toString();
// else 
Double dS = 11.6;
String sdouble = dS.toString();

// compare two double variables
	      Double dComp1 = 4.3;
	      if(dComp1.equals(4.3))
	  		System.out.print("true");

	// compares the two specified double values in Java example
	// int i =	compare(double d1, double d2);
	    int i =	Double.compare(11.5, 11.7); // -1 first < second
	    // 0 first == second
	    // 1 first > second
	    System.out.print(i);