无法解析findViewById和onCreate方法

Question

I'm new to android and wanted to do a simple program, but while I'm coding the Android Studio doesn't understand findViewById and onCreate and etc that I've mentioned in the code. Here is my code and the error is: "Cannnot resolve...."

package ir.maharban.measuretechs;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import ir.maharban.measuretechs.R;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        Button btnCalc = (Button)findViewById(R.id.btnCalc);

    }


}

My Code

Answer 1

Try to clean your project maybe. Build > clean project.

Answer 2

1. Please be patient. Studio takes some time to settle.
2. Try cleaning the project & Rebuild.
3. Try updating your repositories.

Answer 3

have you add this Library App compact in your project

just write this code in your build project:

dependencies {
    compile 'com.android.support:support-v4:18.0.+'
    compile 'com.android.support:appcompat-v7:18.0.+'
}

and Rebuild your android Studio this will run perfect !

Hope this will help you ! Cheers !