1         Button button2=(Button)findViewById(R.id.button_2);
 2         button2.setOnClickListener(new View.OnClickListener() {
 3             @Override
 4             public void onClick(View v) {
 5                 Toast.makeText(FirstActivity.this,"只有不学习的人才会按这个按钮",
 6                         Toast.LENGTH_SHORT).show();
 7             }
 8         });
 9         Button button3=(Button)findViewById(R.id.button_3);
10         button3.setOnClickListener(new View.OnClickListener() {
11             @Override
12             public void onClick(View v) {
13                Intent intent=new Intent(FirstActivity.this,SecondActivity.class);
14                startActivity(intent);
15             }
16         });

cannot resolve symbol'Intent'

import android.content.Intent;