获取EditText的值并弹出提示

package com.example.administrator.tableuse;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends AppCompatActivity {    private EditText mEt;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.layout);        mEt = (EditText) findViewById(R.id.num1);        String num = mEt.getText().toString();        Toast.makeText(this, num,5000).show();    }}