所有的R.都报错了 包括自动生成的代码 小弟初学Android 希望各位前辈多多指教 谢谢了

import android.support.v7.app.ActionBarActivity;

import android.support.v7.app.ActionBar;

import android.support.v4.app.Fragment;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.ViewGroup;

import android.os.Build;

import android.app.Activity;

import android.view.View.OnClickListener;

import android.widget.AdapterView;

import android.widget.ArrayAdapter;

import android.widget.Spinner;

import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

       Spinner spinner=(Spinner)findViewById(R.id.spinner);

       ArrayAdapter adapter=ArrayAdapter.createFromResource(this,R.array.colors,

               android.R.layout.simple_spinner_item);

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        spinner.setAdapter(adapter);

        AdapterView.OnItemSelectedListener oisl=new AdapterView.OnItemSelectedListener() {

            @Override

            public void onItemSelected(AdapterView<?> adapterView, View view, int position,

                                       long id) {

                String selected=adapterView.getItemAtPosition(position).toString();

                System.out.println("selected");

            }

            @Override

            public void onNothingSelected(AdapterView<?> adapterView) {

                System.out.println("nothingSelected");

            }

        };

        spinner.setOnItemSelectedListener(oisl);

    }