Android入门 简易计算器

第一个上手的安卓小项目，包含两个界面：login和calculator。
功能比较简单粗糙，目的主要是熟悉android基本结构与操作。

环境

• Android Studio + Genymotion

演示

login

calculator

详解

布局layout文件之login.xml

布局layout文件之activity_main.xml

drawable文件中buttonstyle.xml

drawable文件中circle.xml

values文件中colors.xml

    #008577
    #00574B
    #D81B60
    #C0C0C0
    #C75A

values文件中strings.xml

    mycalculator

values文件中styles.xml

Login.java

package com.example.mycalculator;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.WindowManager;
import android.app.Activity;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

public class Login extends AppCompatActivity{

    private EditText et_username;
    private EditText et_password;
    private Button bt_log;
    private Button bt_bos;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        //透明状态栏          
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION);

        //通过资源标识获得控件实例
        et_username = (EditText) findViewById(R.id.username);
        et_password = (EditText) findViewById(R.id.password);
        bt_log = (Button) findViewById(R.id.login);
        bt_bos = (Button) findViewById(R.id.cancel);

        //给登录按钮注册监听器，实现监听器接口，编写事件
        bt_log.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //获取用户输入的数据
                String strUsername = et_username.getText().toString();
                String strPassword = et_password.getText().toString();

                //判断用户名和密码是否正确（为可以进行测试，将用户名和密码都定义为admin）
                if(strUsername.equals("admin") && strPassword.equals("admin")){
                    Toast.makeText(Login.this,"用户名和密码正确！",Toast.LENGTH_SHORT).show();
                    //创建一个Intent的实例
                    Intent intent = new Intent();
                    //设置从哪个activity启动哪个activity
                    intent.setClass(Login.this, MainActivity.class);
                    //启动另一个activity
                    startActivity(intent);
                }else {
                    Toast.makeText(Login.this,"用户名或密码错误！",Toast.LENGTH_SHORT).show();
                }

            }
        });
        //给取消按钮注册监听器，实现监听器接口，编写事件
        bt_bos.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }
}

MainActivity.java

package com.example.mycalculator;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    Button zero;
    Button one;
    Button two;
    Button three;
    Button four;
    Button five;
    Button six;
    Button seven;
    Button eight;
    Button nine;
    Button point;
    Button clear;
    Button add;
    Button substraction;
    Button mulitipliction;
    Button division;
    Button root;
    Button surplus;
    Button equal;
    Button delete;
    TextView theFirstView;
    TextView theOptionView;
    TextView theSecondView;
    TextView theEqualView;
    TextView theAnswerView;
    String option = "";
    String str1 = "", str2 = "";
    double number1, number2;
    int answerFlag = 0;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();  //初始化布局
    }

    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.zero:
            case R.id.one:
            case R.id.two:
            case R.id.three:
            case R.id.four:
            case R.id.five:
            case R.id.six:
            case R.id.seven:
            case R.id.eight:
            case R.id.nine:
                if (answerFlag == 0) {
                    if (option == "") {
                        str1 = str1 + ((Button) view).getText().toString();
                        theFirstView.setText(str1);
                    } else {
                        str2 = str2 + ((Button) view).getText().toString();
                        theSecondView.setText(str2);
                    }
                }

                if (answerFlag == 1) {
                    clear();
                    answerFlag = 0;
                    str1 = str1 + ((Button) view).getText().toString();
                    theFirstView.setText(str1);
                }

                break;

            case R.id.point:
                if (str1 != "" && option == "") {
                    str1 = str1 + ((Button) view).getText().toString();
                    theFirstView.setText(str1);
                }
                if (option != "" && str2 != "") {
                    str2 = str2 + ((Button) view).getText().toString();
                    theSecondView.setText(str2);
                } else {
                    //什么都不执行
                }
                break;

            case R.id.add:
                option = "+";
                theOptionView.setText("+");
                break;

            case R.id.substraction:
                option = "-";
                theOptionView.setText("-");
                break;

            case R.id.mulitipliction:
                option = "×";
                theOptionView.setText("×");
                break;

            case R.id.division:
                option = "÷";
                theOptionView.setText("÷");
                break;

            case R.id.surplus:
                option = "%";
                theOptionView.setText("%");
                break;

            case R.id.root:
                if (str1 == "") {
                    option = "√";
                    theOptionView.setText("√");
                }
                break;

            case R.id.clear:
                clear();
                break;

            case R.id.delete:
                if (theAnswerView.getText().toString() == "") {
                    if ((theSecondView.getText().toString()) != "") {
                        int length = str2.length();
                        if (length == 1) {
                            theSecondView.setText("");
                        } else {
                            str2 = str2.substring(0, length - 1);
                            theSecondView.setText(str2);
                        }
                        break;
                    }
                    if ((theSecondView.getText().toString()) == "" && (theOptionView.getText().toString()) != "") {
                        theOptionView.setText("");
                        break;
                    }
                    if ((theSecondView.getText().toString()) == "" && (theAnswerView.getText().toString()) == "" && (theFirstView.getText().toString()) != "") {
                        int length = str1.length();
                        if (length == 1) {
                            theFirstView.setText("");
                        } else {
                            str1 = str1.substring(0, length - 1);
                            theFirstView.setText(str1);
                        }
                        break;
                    }
                }
                break;


            case R.id.equal:
                theEqualView.setText("=");
                answerFlag = 1;

                if (option == "+") {
                    number1 = Double.parseDouble(theFirstView.getText().toString());
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    theAnswerView.setText((number1 + number2) + "");
                }
                if (option == "-") {
                    number1 = Double.parseDouble(theFirstView.getText().toString());
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    theAnswerView.setText((number1 - number2) + "");
                }
                if (option == "×") {
                    number1 = Double.parseDouble(theFirstView.getText().toString());
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    theAnswerView.setText((number1 * number2) + "");
                }
                if (option == "÷") {
                    number1 = Double.parseDouble(theFirstView.getText().toString());
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    if (number2 == 0) {
                        theAnswerView.setText("错误");
                    } else {
                        theAnswerView.setText((number1 / number2) + "");
                    }
                }
                if (option == "√") {
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    theAnswerView.setText(Math.sqrt(number2) + "");
                }
                if (option == "%") {
                    number1 = Double.parseDouble(theFirstView.getText().toString());
                    number2 = Double.parseDouble(theSecondView.getText().toString());
                    theAnswerView.setText(number1 % number2 + "");
                }
                break;

        }
    }


    public void initView() {
        zero = (Button) findViewById(R.id.zero);
        one = (Button) findViewById(R.id.one);
        two = (Button) findViewById(R.id.two);
        three = (Button) findViewById(R.id.three);
        four = (Button) findViewById(R.id.four);
        five = (Button) findViewById(R.id.five);
        six = (Button) findViewById(R.id.six);
        seven = (Button) findViewById(R.id.seven);
        eight = (Button) findViewById(R.id.eight);
        nine = (Button) findViewById(R.id.nine);
        point = (Button) findViewById(R.id.point);
        clear = (Button) findViewById(R.id.clear);
        add = (Button) findViewById(R.id.add);
        substraction = (Button) findViewById(R.id.substraction);
        mulitipliction = (Button) findViewById(R.id.mulitipliction);
        division = (Button) findViewById(R.id.division);
        root = (Button) findViewById(R.id.root);
        surplus = (Button) findViewById(R.id.surplus);
        equal = (Button) findViewById(R.id.equal);
        delete = (Button) findViewById(R.id.delete);
        theFirstView = (TextView) findViewById(R.id.the_first_number);
        theOptionView = (TextView) findViewById(R.id.the_option);
        theSecondView = (TextView) findViewById(R.id.the_second_number);
        theEqualView = (TextView) findViewById(R.id.the_equal);
        theAnswerView = (TextView) findViewById(R.id.the_answer);

        zero.setOnClickListener(this);
        one.setOnClickListener(this);
        two.setOnClickListener(this);
        three.setOnClickListener(this);
        four.setOnClickListener(this);
        five.setOnClickListener(this);
        six.setOnClickListener(this);
        seven.setOnClickListener(this);
        eight.setOnClickListener(this);
        nine.setOnClickListener(this);
        point.setOnClickListener(this);
        clear.setOnClickListener(this);
        add.setOnClickListener(this);
        substraction.setOnClickListener(this);
        mulitipliction.setOnClickListener(this);
        division.setOnClickListener(this);
        root.setOnClickListener(this);
        surplus.setOnClickListener(this);
        equal.setOnClickListener(this);
        delete.setOnClickListener(this);
        theFirstView.setOnClickListener(this);
        theOptionView.setOnClickListener(this);
        theEqualView.setOnClickListener(this);
        theSecondView.setOnClickListener(this);
        theAnswerView.setOnClickListener(this);
    }

    public void clear() {
        str1 = "";
        str2 = "";
        theFirstView.setText("");
        theSecondView.setText("");
        theOptionView.setText("");
        theEqualView.setText("");
        theAnswerView.setText("");
        option = "";
    }
}

Manifests文件中AndroidManifest.xml