Android Widget OnClick Example

public class Main extends Activity {

private TextView mTextView;
private Activity mAct;
private Intent mIntent;

protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main_layout);
  mTextView = findViewById(R.id.mTextView);
  mAct = getActivity();
  mIntent = getIntent();
 }

}

public class Main extends Fragment{

 private TextView mTextView;
 private FragmentActivity mFrgAct;
 private Intent mIntent;
 private LinearLayout mLinearLayout;
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
          Bundle savedInstanceState) {
          View root = inflater.inflate(R.layout.fragment_main, null);
        return root;
    }

 public void onViewCreated(View view, Bundle savedInstanceState) {
          // you can add listener of elements here
          /*Button mButton = (Button) view.findViewById(R.id.button);
            mButton.setOnClickListener(this); */
          mTextView = view.findViewById(R.id.mTextView);
          mLinearLayout = (LinearLayout)view;
 }
 public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
          mFrgAct = getActivity();
          mIntent = mFrgAct.getIntent(); //  Intent intent = new Intent(getActivity().getIntent());
 }

}

String sFileContent = readFile("myfile.txt",StandardCharsets.UTF_8);

	static String readFile(String path, Charset encoding) 
		  throws IOException 
		{
		  byte[] encoded = Files.readAllBytes(Paths.get(path));
		  return encoding.decode(ByteBuffer.wrap(encoded)).toString();
		}

// write file
String sOut = "text blah hello world etc.";
		writeToFile(sOut"someName.txt");	
	static void writeToFile(String sB,String name) {
		String folder = ("c:\\folder\\");
		File f = new File(folder+ name);
		BufferedWriter writer = null;
			writer = new BufferedWriter( new OutputStreamWriter(
                           new FileOutputStream( folder+name),"UTF-8"));
			writer.write( sB);

				if ( writer != null)
					writer.close( );
	}

// Context instead Activity as a parameter
@Override
public void onAttach(Context context) {
    super.onAttach(context);

    Activity a;

    if (context instanceof Activity){
        a=(Activity) context;
    }

}

OnNoteClickedListener listener;
/* old emxample of usage
	@Override
	public void onAttach(Activity activity) {
		super.onAttach(activity);
		try {
			listener = (OnNoteClickedListener) activity;
		} catch (ClassCastException e) {
			throw new ClassCastException(activity.toString()
					+ " must implement OnNoteClickedListener");
		}
	}
*/
// new version of code
	@Override
	public void onAttach(Context context) {
		super.onAttach(context);

		Activity a;

		if (context instanceof Activity){
			a=(Activity) context;
			try {
				listener = (OnNoteClickedListener) a;
			} catch (ClassCastException e) {
				throw new ClassCastException(a.toString()
						+ " must implement OnNoteClickedListener");
			}
		}

	}

Context context = getApplicationContext();
String DB_PATH = "/data/data/"
                + context.getPackageName()
                + "/databases/";