Difference between “@+id/” and “@id/” in Android

"id cannot be resolved or is not a field” error
If you copy project to workspace or some code from other project you can get this error.

Try remove or add import your R file:

import com.example.app.R

Check xml files.
Clean project by menu Project-Clean

Maybe you have to create new project end copy old source files to new project folders.

Button, setOnClickListener, Intent.ACTION_VIEW, startActivity Android example.

Button mIdButtonHome = (Button)findViewById(R.id.idButtonHome);
	mIdButtonHome.setOnClickListener(new View.OnClickListener() {
		public void onClick(View v) {
			Intent browserIntent = new Intent(
					Intent.ACTION_VIEW,
					Uri.parse("//android.okhelp.cz/category/software/"));
			startActivity(browserIntent);
		}
	});

public class ApokusActivity extends Activity {
	
	@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);
            
           Bitmap b = Bitmap.createBitmap(200, 200, Bitmap.Config.ALPHA_8);
           Canvas c = new Canvas(b);
           c.drawRect(0, 0, 200, 200, paint);
           
           paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
           paint.setTextSize(40);
           paint.setTextScaleX(1.f);
           paint.setAlpha(0);
           paint.setAntiAlias(true);
           c.drawText("Your text", 30, 40, paint);
           paint.setColor(Color.RED);
           
           canvas.drawBitmap(b, 10,10, paint);
		}

	}
}

Call requires API level 16 (current min is 4): android
Change The SDK version in AndroidManifest.xml to higher

<uses-sdk android:minSdkVersion="4" />
// 
<uses-sdk android:minSdkVersion="8" />

Check your xml files in Eclipse Graphical Editor and fix problems.



Check project setup, right click on project, select properties, Java build path and
select correct Android version etc.


Right click on project, Android Tools, Fix Project Properties

Menu Eclipse select Project ->Clean.