Problem: erroneous entry of id

<RadioButton android:id="idRadio"
                android:text="My radio button"/>

Solution: @+id/

<RadioButton android:id="@+id/idRadio"
                android:text="My radio button"/>

Emulator window was out of view and was recentred
Emulator] WARNING: Data partition already in use. Changes will not persist!
Emulator] WARNING: SD Card image already in use: C:\Documents and Settings\user_name\.android\avd\hvga21_up1_7.avd/sdcard.img
Emulator] WARNING: Cache partition already in use. Changes will not persist!

Basic step
Try restart Eclipse if using from menu File->Restart

Other solutions

Solution 1: try restart ADB server
//android.okhelp.cz/how-quickly-restart-adb-exe-adb-server-android-emulator-example/


Solution 2:

Delete Run Configuration

//android.okhelp.cz/android-emulator-wont-run-application-started-from-eclipse/





Solution 3:
Try delete:

c:\Documents and Settings\user_name\.android\avd\my_avd.avd\cache.img
c:\Documents and Settings\user_name\.android\avd\my_avd.avd\userdata-qemu.img

Try solution 4:
Eclipse menu select Window->Preferences->Android

Windows 32

FROM: C:\Program Files\Android\android-sdk
TO: C:\PROGRA~1\Android\android-sdk

Windows 64

FROM: C:\Program Files (x86)\Android\android-sdk
TO: C:\PROGRA~2\Android\android-sdk

/* 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();
            }
        });	
 	}

}

Landscape - portrait orientation change:

boolean mbOrientationLandscape = true;
if(mbOrientationLandscape ){
	setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
	mbOrientationLandscape =false;
}else{
	setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
	mbOrientationLandscape =true;
}

Link to tutorial

ArrayList Sublist of ArrayList Join two ArrayList Compare ArrayList Initialize ArrayList Loop ArrayList Sort ArrayList Array to ArrayList ArrayList to Array Synchronize ArrayList Serialize ArrayList LinkedList Loop LinkedList Vector ArrayList vs Vector ArrayList vs LinkedList HashMap Loop HashMap Synchronize HashMap Sort HashMap Serialize HashMap ArrayList vs HashMap TreeMap LinkedHashMap HashSet TreeSet LinkedHashSet ArrayList Methods