TodoListActivity.java

package com.example.todos;

import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class TodoListActivity extends AppCompatActivity {

    String[] itemname ={
            "Get theatre tickets",
            "Order pizza for tonight",
            "Buy groceries",
            "Running session at 19.30",
            "Call Uncle Sam"
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        final ListView lv=(ListView) findViewById(R.id.lvTodos);
//adds the custom layout
        lv.setAdapter(new ArrayAdapter<String>(this, R.layout.todo_list_item,
                R.id.tvNote,itemname));
//adds the click event to the listView, reading the content
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int pos, long id) {
                Intent intent = new Intent(TodoListActivity.this, TodoActivity.class);
                String content= (String) lv.getItemAtPosition(pos);
                intent.putExtra("Content", content);
                startActivity(intent);
            }
        });

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }
}

hello can you help me please...i have a problem...
i cant import this 4 lines:
import android.support.design.widget.FloatingActionButton; //cannot resolve symbol design (unused import statement)
import android.support.design.widget.Snackbar; //cannot resolve symbol design (unused import statement)
import android.support.v7.app.AppCompatActivity; //cannot resolve symbol v7 (unused import statement)
import android.support.v7.widget.Toolbar; cannot resolve symbol v7 (unused import statement)