Android studio 在android studio中，我被错误所困扰；R无法解决”；

自从我打开java文件以来，我一直无法修复这个错误。我总是以同样的方式设置代码，这是我第一次遇到这个错误，我尝试打开一个新文件并将我的代码粘贴到他们的文件中，但它无法修复它

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    int turn=1;
    public void tile1(ImageView i) {
        ImageView tile1 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile1.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile1.setImageResource(R.drawable.grape);
        }
    }
    public void tile2(ImageView i) {
        ImageView tile2 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile2.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile2.setImageResource(R.drawable.grape);
        }
    }
    public void tile3(ImageView i) {
        ImageView tile3 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile3.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile3.setImageResource(R.drawable.grape);
        }
    }
    public void tile4(ImageView i) {
        ImageView tile4 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile4.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile4.setImageResource(R.drawable.grape);
        }
    }
    public void tile5(ImageView i) {
        ImageView tile5 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile5.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile5.setImageResource(R.drawable.grape);
        }
    }
    public void tile6(ImageView i) {
        ImageView tile6 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile6.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile6.setImageResource(R.drawable.grape);
        }
    }
    public void tile7(ImageView i) {
        ImageView tile7 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile7.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile7.setImageResource(R.drawable.grape);
        }
    }
    public void tile8(ImageView i) {
        ImageView tile8 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile8.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile8.setImageResource(R.drawable.grape);
        }
    }
    public void tile9(ImageView i) {
        ImageView tile9 = (ImageView) findViewById(R.id.turn);
        if (turn == 1) {
            turn = 2;
            tile9.setImageResource(R.drawable.apple);
        } else {
            turn = 1;
            tile9.setImageResource(R.drawable.grape);
        }
    }
}

可能的重复可能的重复