Android TextView button控件001

1.新建一个TextView控件 firsttext
2.新建一个button
3.添加如下代码

package com.example.administrator.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

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

    int size = 30;
    public void bigger(View v){
        TextView txv;
        txv=findViewById(R.id.firsttext);
        txv.setTextSize(++size);

    }
}