Unable to find explicit activity class Android Eclipse error

 java.io.InputStream is;
is = context.getResources().openRawResource(R.drawable.my_image);

Drawable mDrawable = context.getResources().getDrawable(R.drawable.button);
mDrawable.setBounds(150, 20, 300, 100);


Drawable[] mDrawables;
int[] resIDs = new int[] {
                R.drawable.btn_ok,
                R.drawable.btn_storno,
                R.drawable.btn_help
            };
            mDrawables = new Drawable[resIDs.length];
            Drawable prev = mDrawable;
            for (int i = 0; i < resIDs.length; i++) {
                mDrawables[i] = context.getResources().getDrawable(resIDs[i]);
                mDrawables[i].setDither(true);
                addToTheRight(mDrawables[i], prev);
                prev = mDrawables[i];
            }

       <RadioGroup android:id="@+id/idRadio_group"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="20dp"
            android:orientation="vertical">

            <RadioButton android:id="@+id/idRadio_1"
                android:text="@string/textLabel_1"/>
            <RadioButton android:id="@+id/idRadio_2"
                android:text="@string/textLabel_2"/>
            <RadioButton android:id="@+id/idRadio_3"
                android:text="@string/textLabel_3"/>

        </RadioGroup>

// import
import android.widget.RadioGroup;
// get handle of RadioGroup
RadioGroup  mRadioGroup = (RadioGroup) findViewById(R.id.idRadio_group);

// which RadioButton is selected for example in some function body
         int nUnits = 10; // decimetry
    	 int nIdRadio = mRadioGroup.getCheckedRadioButtonId();
    			if(nIdRadio == R.id.idRadio_1) nUnits = 1; // metr
    			else if(nIdRadio == R.id.idRadio_2) nUnits = 10; // decimetr
    			else if(nIdRadio == R.id.idRadio_3) nUnits = 100; // cm
    			else if(nIdRadio == R.id.idRadio_4) nUnits = 1000; // mm


// listener for RadioGroup Java Android example
       mRadioGroup.setOnCheckedChangeListener(
                new RadioGroup.OnCheckedChangeListener() {
                    public void onCheckedChanged(RadioGroup group,
                            int checkedId) {
                        Log.v("Selected", "New radio item selected: " + checkedId);
                        recordNewUIState();
                    }
                });

public class MainActivity extends Activity {
Boolean bColorYellow = true;
TextView hTextView;
TableRow hTableRow;
@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        hTextView = (TextView)findViewById(R.id.idTextView);
        hTableRow = (TableRow)findViewById(R.id.idTableRow1);


        
        
    } // end onCreate
  
    
    public void myTableRowClickHandler(View view) {
		switch (view.getId()) {
		case R.id.idTableRow1:{
			
			if(bColorYellow){
			hTableRow.setBackgroundColor(Color.GREEN);
			bColorYellow = false;
			}
			else{
			hTableRow.setBackgroundColor(Color.YELLOW);
			bColorYellow = true;
			}
		}
		break;
		}
  }
}

<?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"
    >


<TableLayout android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/tableLayout1">
    <TableRow android:id="@+id/idTableRow1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:background="#5655AA"
    android:onClick="@string/myTableRowClick"
    android:focusable="true">
<TextView  
	android:id="@+id/idTextView"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
    
    </TableRow>
</TableLayout>
    
    
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello">Hello World!</string>
    <string name="app_name">TableRow</string>
    <string name="myTableRowClick">myTableRowClickHandler</string>
</resources>

// error
InputStream is = context.getResources().openRawResource(R.drawable.app_sample_code);

// ok
InputStream is = context.getResources().openRawResource(+R.drawable.app_sample_code);

	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
			setContentView(R.layout.main);

         // in onCreate
         PackageInfo pinfo = this.getPackageManager().getPackageInfo(getPackageName(), 0);
         String sVersionCode = pinfo.versionCode; // 1
         String sVersionName = pinfo.versionName; // 1.0
         String sPackName = getPackageName(); // cz.okhelp.my_app
         int nSdkVersion = Integer.parseInt(Build.VERSION.SDK); // 7
         int nSdkVers = Build.VERSION.SDK_INT; // 7

       }

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="//schemas.android.com/apk/res/android"
      package="cz.okhelp.my_app"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="7" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Add_view_to_tableActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
</manifest>