安卓学习：简易乘法计算

输入框最大输入长度：android:maxLength=“7”
只允许输入数字：android:numeric=“integer”
禁止输入：android:focusable=“false”

效果：

实现：
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:background="@drawable/background"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <LinearLayout
        android:gravity="center"
        android:layout_width="350dp"
        android:layout_height="60dp">
        
        <EditText
            android:gravity="center"
            android:id="@+id/edt1"
            android:layout_width="90dp"
            android:layout_height="60dp"
            android:numeric="integer"
            android:maxLength="7"
            android:background="@drawable/costom"
            android:ems="10"/>
        <TextView
            android:gravity="center"
            android:layout_width="50dp"
            android:layout_height="60dp"
            android:text="+"
            android:textSize="50sp"/>

        <EditText
            android:id="@+id/edt2"
            android:layout_width="90dp"
            android:layout_height="60dp"
            android:gravity="center"
            android:maxLength="7"
            android:numeric="integer"
            android:background="@drawable/costom"
            android:ems="10"/>
        <TextView
            android:gravity="center"
            android:layout_width="50dp"
            android:layout_height="60dp"
            android:text="="
            android:textSize="50sp"/>

        <EditText
            android:id="@+id/edt3"
            android:layout_width="90dp"
            android:layout_height="60dp"
            android:gravity="center"
            android:focusable="false"
            android:background="@drawable/costom"
            android:ems="10"/>
    </LinearLayout>
    <LinearLayout
        android:layout_marginTop="20dp"
        android:gravity="center"
        android:layout_width="350dp"
        android:layout_height="60dp">

        <Button
            android:layout_width="100dp"
            android:layout_height="60dp"
            android:text="计算"
            android:textSize="25sp"
            android:onClick="doCalculation"/>
        <Button
            android:layout_width="100dp"
            android:layout_height="60dp"
            android:text="清空"
            android:textSize="25sp"
            android:onClick="doClear"/>
        <Button
            android:layout_width="100dp"
            android:layout_height="60dp"
            android:text="退出"
            android:textSize="25sp"
            android:onClick="doExit"/>
    </LinearLayout>
</LinearLayout>

编写输入框样式(drawable下）
costom.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <solid android:color="#FFFFFF"/>
            <stroke android:width="1dip" android:color="#F0F0F0"/>
        </shape>
    </item>
</selector>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {
    private EditText edt1,edt2, edt3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        edt1 = findViewById(R.id.edt1);
        edt2 = findViewById(R.id.edt2);
        edt3 = findViewById(R.id.edt3);
    }

    public void doCalculation(View view) {
        int num1 = Integer.parseInt(edt1.getText().toString());
        int num2 = Integer.parseInt(edt2.getText().toString());
        int num3 = num1 * num2;
        edt3.setText(num3+"");

    }

    public void doClear(View view) {
        edt1.setText("");
        edt2.setText("");
        edt3.setText("");
    }

    public void doExit(View view) {
        finish();
    }
}