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onSaveInstanceState() onRestoreInstanceState() basic Android example




public class MyClass extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       }
	 String sMyText = "some text";
	 int nMyInt = 10;

 @Override
 protected void onSaveInstanceState(Bundle outState) {
     // Save away the original text, so we still have it if the activity
     // needs to be killed while paused.
     outState.putString("my_text", sMyText);
     outState.putInt("my_int", nMyInt);
     Toast.makeText(this, "onSaveInstanceState()", Toast.LENGTH_LONG).show();
Log.i("onSaveInstanceState", "onSaveInstanceState()");
}
 String sNewMyText = "";
 int nNewMyInt = 0;
 
 @Override
 protected void onRestoreInstanceState(Bundle savedInstanceState) {
     super.onRestoreInstanceState(savedInstanceState);
     // restore saved values
     sNewMyText = savedInstanceState.getString("my_text");
     nNewMyInt = savedInstanceState.getInt("my_int");
     Toast.makeText(this, "onRestoreInstanceState()", Toast.LENGTH_LONG).show();
     Log.i("onRestoreInstanceState", "onRestoreInstanceState()");
     
 }
}

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android.app.Application cannot be cast to android.app.Activity | android-app-application-cannot-be-cast-to-android-app-activity


If you using Context as parameter of function try this solution:

public class MyActivity extends Activity {
// bla bla bla .......
//error 
myFc( getapplicationcontext());
// OK
myFc(MyActivity.this);
330

Screen size density independent pixel resolution | screen-size-density-independent-pixel-resolution


Terms Screen size, density, density independent pixel, resolution as a picture - pictogram.
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Test your knowledge
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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?
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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.

 

 
217

How to programmatically set the button style - Android | how-to-programmatically-set-the-button-style-android


How set rounded corners and own styles ActivityMy.java

Button btn.setBackgroundResource(R.drawable.back_button_answer);



\res\drawable\back_button_answer.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="//schemas.android.com/apk/res/android" android:shape="rectangle" >
   <corners android:radius="10dip" />
   <!-- background -->
   
   <gradient
                android:startColor="#D6D7D6"
                android:centerColor="#E2E2E2"
                android:centerY="0.75"
                android:endColor="#D6D7D6"
                android:angle="270"
        />
   
   <stroke android:width="2dip" android:color="#fff"/>
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225

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If you try function for checking internet connection you can disable internet on the emulator:
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 public boolean isNetworkAvailable() {
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139

drawBitmap createBitmap by array of colours Android example | drawbitmap-createbitmap-draw-bitmap-by-array-of-colours-android-example


public static Bitmap createBitmap (int[] colors, int offset, int stride, int width, int height, Bitmap.Config config)
public void drawBitmap (Bitmap bitmap, float left, float top, Paint paint)

//  //www.apache.org/licenses/LICENSE-2.0
public class MainActivity extends Activity {
	    private static final int WIDTH = 50;
	    private static final int HEIGHT = 50;
	    private static final int STRIDE = 64;   // must be >= WIDTH
	    
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	        int[] colors = new int[STRIDE * HEIGHT];
	        for (int y = 0; y < HEIGHT; y++) {
	            for (int x = 0; x < WIDTH; x++) {
	                int r = x * 255 / (WIDTH - 1);
	                int g = y * 255 / (HEIGHT - 1);
	                int b = 255 - Math.min(r, g);
	                int a = Math.max(r, g);
	                colors[y * STRIDE + x] = (a << 24) | (r << 16) | (g << 8) | b;
	            }
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	        return colors;
	    }
	
	@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);

		}
		@Override
		protected void onDraw(Canvas canvas) {
			Paint paint = new Paint();
			
			canvas.drawColor(Color.GREEN);

            int[] mColors = createColors();
            int[] colors = mColors;

           
            Bitmap bitmap = Bitmap.createBitmap(colors, 0, STRIDE, WIDTH, HEIGHT,
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			canvas.drawBitmap(bitmap, 50,20, paint); 
		}

	}
}




Editace Jana Žákovská : 2011-10-08 15:38:52
Počet článků v kategorii: 397
Url:onsaveinstancestate-onrestoreinstancestate-basic-android-example
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