break statement in Java Android example

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.

 

 

Toast in Android application is equivalent of Alert in JavaScript or MessageBox in WinApi.

// Toast android.widget.Toast.makeText(Context context, CharSequence text, int duration)
// public static Toast makeText (Context context, CharSequence text, int duration) 

Toast.makeText(getApplicationContext(), "Hello world!",
                  Toast.LENGTH_SHORT).show();

/* Copyright (C) 2011 The Android Open Source Project
//www.apache.org/licenses/LICENSE-2.0
*/
public class MainActivity extends Activity {
private ImageView imageView;
private Button button1;
Drawable bitmapOrg;
private final int[] mColors =
{Color.BLUE, Color.GREEN, Color.RED, Color.LTGRAY, Color.MAGENTA, Color.CYAN,
		Color.YELLOW, Color.WHITE};
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		imageView = (ImageView)findViewById(R.id.imageView1);
		button1 = (Button)findViewById(R.id.button1);

		
		bitmapOrg = this.getResources().getDrawable(R.drawable.flower_blue);
        
        button1.setOnClickListener(new OnClickListener() {
            public void onClick(View view) {
                int mColor = (int) Math.floor(Math.random() * mColors.length);
                bitmapOrg.setColorFilter(mColors[mColor], PorterDuff.Mode.MULTIPLY);
                imageView.setImageDrawable(bitmapOrg);
                imageView.invalidate();
            }
        });	
 	}

}

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

How to resize an image in ImageView Android source code.
Resize imageview layout and image will resize too:

	public void resizeImageView(int width, int height) {
		final ImageView picture1 = (ImageView)findViewById(R.id.imageView1);
		LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(width, height);
		picture1.setLayoutParams(layoutParams);
	}