R Errors In Eclipse [duplicate]

Question

This question already has answers here:

R cannot be resolved - Android error (108 answers)

Closed 8 years ago.

package de.vogella.android.sqlite.first;

import java.util.List;
import java.util.Random;

import android.R;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;

public class TestDatabaseActivity extends ListActivity {
  private CommentsDataSource datasource;

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

    datasource = new CommentsDataSource(this);
    datasource.open();

    List<Comment> values = datasource.getAllComments();

    // use the SimpleCursorAdapter to show the
    // elements in a ListView
    ArrayAdapter<Comment> adapter = new ArrayAdapter<Comment>(this,
        android.R.layout.simple_list_item_1, values);
    setListAdapter(adapter);
  }

  // Will be called via the onClick attribute
  // of the buttons in main.xml
  public void onClick(View view) {
    @SuppressWarnings("unchecked")
    ArrayAdapter<Comment> adapter = (ArrayAdapter<Comment>) getListAdapter();
    Comment comment = null;
    switch (view.getId()) {
    case R.id.add:
      String[] comments = new String[] { "Cool", "Very nice", "Hate it" };
      int nextInt = new Random().nextInt(3);
      // save the new comment to the database
      comment = datasource.createComment(comments[nextInt]);
      adapter.add(comment);
      break;
    case R.id.delete:
      if (getListAdapter().getCount() > 0) {
        comment = (Comment) getListAdapter().getItem(0);
        datasource.deleteComment(comment);
        adapter.remove(comment);
      }
      break;
    }
    adapter.notifyDataSetChanged();
  }

  @Override
  protected void onResume() {
    datasource.open();
    super.onResume();
  }

  @Override
  protected void onPause() {
    datasource.close();
    super.onPause();
  }

} 

This is my code above.

The three errors that I am receiving are:

setContentView(R.layout.main); 
                         ^
                      main cannot be resolved or is not a field

&&&

case R.id.add:
           ^
        add cannot be resolved or is not a field

&&&

case R.id.delete:
           ^
        delete cannot be resolved or is not a field

Answer 1

You have to remove
import android.R

Then clean and rebuild project. R will be generated.

Answer 2

Remove the import to android.R

It is getting confused by the namespaces

Answer 3

import android.R; 

instead use

import yourpackgename.R;

Answer 4

first remove the import

import android.R;

and then go to line

setContentView(R.layout.main); 

and hover it and add the import of your main package and after then import android.R;