R.layout.activity_main出错
package com.ab.helloworld;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
R下面有波浪线 提示R cannot be resolved to a variable这是怎么回事
