Center View in RelativeLayout Android

Terms Screen size, density, density independent pixel, resolution as a picture - pictogram.


Test your knowledge
Q: How to find out the phone screen size?
A: (By length of display diagonale in inch -  Not to measure a diagonal of device!!!)

Q: What resolution has 720 x 1280 display?
A: (921600 pixels)

Q: What does it mean "240 dpi" screen density?
A: (Display have density 240 x 240  dots - "Tri-color LED etc." - per every physical (real) square inch. If you have icon 240x240 pixels, this will just occupy an area of one square inch on the display.)

Q: Phone have screen density 240 dpi. Image for 160 dpi screen density have size 128x 128 pixels. What will be the size of the image for 240 dpi screen density?
A: (Calculate the virtual pixels size.   128 * (240/160)  =  192.  You have to resize image to new size 192 x 192 physical pixels and put into folder drawable-hdpi (high) ~240dpi  for phone with screen density 240 dpi. ) or use density independend pixels 128dp x 128dp.

 

 

Unable to resolve target android-7
Try this solution:
Select project from tree (project explorer)
- right click on project
- properties
- select Android from tree
- change Project Build Target to higher (or change project build target)
- selct from menu: Project-Clean ( select your project - OK)

Pictures taken by front camera Lenovo A6000 smartpohone - review.
Do not take pictures against the sun.
Stay in the shade. Keep lens clean.

Night without flash









Misty - smog


Without flash in room - TV screen

Update TextView by runnable. Handler, runnable, timer Android example.

public class TimerActivity extends Activity {
TextView hTextView;
Button hButton, hButtonStop;
private Handler mHandler = new Handler();
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) {
		try {
			mHandler.removeCallbacks(hMyTimeTask);
         //        Parameters
         //        r  The Runnable that will be executed. 
         //        delayMillis  The delay (in milliseconds) until the Runnable will be executed. 
                       mHandler.postDelayed(hMyTimeTask, 1000); // delay 1 second
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
};


private Runnable hMyTimeTask = new Runnable() {
	   public void run() {
		   nCounter++;
	    	   hTextView.setText("Hallo from thread counter: " + nCounter);
	   }
	}; 
/**
 * 
 */
    View.OnClickListener mButtonStopListener = new OnClickListener() {
    	public void onClick(View v) {
    		 mHandler.removeCallbacks(hMyTimeTask);
    		
    	}
    };
}

main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="//schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
	android:id="@+id/idTextView"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button android:text="Button" 
android:id="@+id/idButton" 
android:layout_width="wrap_content" 
android:layout_height="wrap_content"></Button>
 
 <Button android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:id="@+id/idButtonStop" 
 android:text="Stop"></Button> 
    
    
</LinearLayout>

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"
 />