안드로이드...

package com.example.administrator.myapplication;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    TextView txt1;
    TextView edit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txt1 = (TextView) findViewById(R.id.txt1);

        txt1.setText(" Hi jinsil");

        Button button = (Button) findViewById(R.id.button);
        button.setText("로그인");

        button.setOnClickListener(this);

        edit = (TextView) findViewById(R.id.edit);
        edit.setHint("수정");
    }


    @Override
    public void onClick(View v) {

        String str;
        str = edit.getText().toString();
//        txt1.setText(str);
//        edit.setText("");
//        Log.d("fff", str);

        int input = Integer.parseInt(str);
        String str2 = "";
        if (1 < input && input < 10) {
            for (int i = 2; i < 10; i++) {
                for (int j = 1; j < 10; j++) {
                    if (input == i) {
                        str2 = str2 + i + "x" + j + "=" + i * j + "\n";
                    }
                }
            }
        } else {
            txt1.setText("2~9까지의 숫자를 적어주세요.");
        }
        txt1.setText(str2);
    }

}

===========================================================================

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/txt1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textSize="20sp"
        android:text="Hello World!"
        android:textColor="#ff0000"/>

    <Button
        android:id="@+id/button"
        android:background="#00ff00"
        android:textSize="22sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/txt1"


        android:text="Button" />

    <EditText
        android:id="@+id/edit"
        android:maxLines="1"
        android:inputType="text"
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:textColor="#ffffff"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/button"
        android:background="#0000ff"
        android:textSize="22sp"
        />

</RelativeLayout>

============================

activity

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/txt1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textSize="20sp"
        android:text="Hello World!"
        android:textColor="#ff0000"/>

    <Button
        android:id="@+id/button"
        android:background="#00ff00"
        android:textSize="22sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/txt1"


        android:text="Button" />

    <EditText
        android:id="@+id/edit"
        android:maxLines="1"
        android:inputType="text"
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:textColor="#ffffff"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/button"
        android:background="#0000ff"
        android:textSize="22sp"
        />

</RelativeLayout>