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double in Java example for Android development


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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);



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Copy save Bitmap Image Pictures Android example | save-bitmap-image-android-example


Copy file to another

        File path = Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_PICTURES);
        File file = new File(path, "MyPicture.jpg");
           // the Pictures directory exists? 
            path.mkdirs();
            InputStream is = getResources().openRawResource(R.drawable.flower_blue);
            OutputStream os = new FileOutputStream(file);
            byte[] data = new byte[is.available()];
            is.read(data);
            os.write(data);
            is.close();
            os.close();


Copy and compress file

Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),
					R.drawable.flower_blue);

try {
	 FileOutputStream out = new FileOutputStream("new_bitmap.jpg");
		bitmapOrg.compress(Bitmap.CompressFormat.JPEG, 90, out);
} catch (Exception e) {
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} 
212

Accessibility Missing contentDescription attribute on image | accessibility-missing-contentdescription-attribute-on-image


Android Emulator warning:[Accessibility] Missing contentDescription attribute on image

Workaround example code:
android:contentDescription="@string/desc"

            <ImageView
                android:id="@+id/imageViewOil"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
            android:contentDescription="@string/desc"
                android:layout_alignParentLeft="true"
                android:layout_centerVertical="true"
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69

Timer task TimerTask run cancel Android example | timer-task-timertask-run-cancel-android-example


Update TextView from TimerTask, Handler, schedule, run, cancel TimerTask, Android example

public class TimerActivity extends Activity {
	TimerTask mTimerTask;
	final Handler handler = new Handler();
	Timer t = new Timer();	
TextView hTextView;
TableRow hTableRow;
Button hButton, hButtonStop;


private int nCounter = 0;
@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        hTextView = (TextView)findViewById(R.id.idTextView);
        hButton = (Button)findViewById(R.id.idButton);
        hButton.setOnClickListener(mButtonStartListener);
        hButtonStop = (Button)findViewById(R.id.idButtonStop);
        hButtonStop.setOnClickListener(mButtonStopListener);

         
        
    } // end onCreate

View.OnClickListener mButtonStartListener = new OnClickListener() {
	public void onClick(View v) {
		doTimerTask();
    }
};



	
	View.OnClickListener mButtonStopListener = new OnClickListener() {
    	public void onClick(View v) {
    		stopTask();
    		
    	}
    };
    
    
    public void doTimerTask(){

    	mTimerTask = new TimerTask() {
    	        public void run() {
    	                handler.post(new Runnable() {
    	                        public void run() {
    	                        	nCounter++;
                                        // update TextView
    	                        	hTextView.setText("Timer: " + nCounter);

    	                        	Log.d("TIMER", "TimerTask run");
    	                        }
    	               });
    	        }};

            // public void schedule (TimerTask task, long delay, long period) 
    	    t.schedule(mTimerTask, 500, 3000);  // 

    	 }

    	  public void stopTask(){

    	   if(mTimerTask!=null){
    	      hTextView.setText("Timer canceled: " + nCounter);

    	      Log.d("TIMER", "timer canceled");
    	      mTimerTask.cancel();
    	 }
    
    }    
}


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Force Screen On - dont use WakeLock - use getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) - Android sample | force-screen-on-dont-use-wakelock-use-getwindow-addflagswindowmanager-layoutparams-flag_keep_screen_on-android-sample


FLAG_KEEP_SCREEN_ON saving energy. Protects the battery if a user closing applications using the Return button on device. The device will returned to user screen mode settings.

@Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        //..........
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
    }
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Programmatically determine if App is running on Android Emulator | programmatically-determine-if-app-is-running-on-android-emulator


You can get list by class Build
For example:

if(Build.MANUFACTURER.equals("unknown")) {
		// Emulator
	}


List of Build class getting from emulator:
"BOARD=unknown
BRAND=generic
CPU_ABI=armeabi
DEVICE=generic
DISPLAY=sdk-eng 2.1-update1 ECLAIR 35983 test-keys
FINGERPRINT=generic/sdk/generic/:2.1-update1/ECLAIR/35983:eng/test-keys
HOST=android-test-13.mtv.corp.google.com
ID=ECLAIR
MANUFACTURER=unknown
MODEL=sdk
PRODUCT=sdk
TAGS=test-keys
TIME=1273161972000
TYPE=eng
USER=android-build
"


Editace: 2011-09-26 20:49:42
Počet článků v kategorii: 397
Url:double-in-java-example-for-android-development

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