帮我用Android Studio 写一个贷款计算器的程序

以下是一个简单的房贷计算器的Android Studio程序，其中包括CheckBox图标的改变、EditText格式的改变、Spinner的使用和房贷的计算逻辑。你可以根据自己的需要进行修改和扩展。

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import java.text.DecimalFormat;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

    private EditText etLoanAmount, etLoanTerm, etInterestRate;
    private TextView tvMonthlyPayment, tvTotalPayment, tvTotalInterest;
    private CheckBox cbTaxes, cbInsurance;
    private Spinner spLoanType;
    private Button btnCalculate;
    private double loanAmount, interestRate, monthlyPayment, totalPayment, totalInterest;
    private int loanTerm, loanType;
    private boolean taxes, insurance;
    private DecimalFormat df = new DecimalFormat("#.##");

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

        etLoanAmount = findViewById(R.id.et_loan_amount);
        etLoanTerm = findViewById(R.id.et_loan_term);
        etInterestRate = findViewById(R.id.et_interest_rate);
        tvMonthlyPayment = findViewById(R.id.tv_monthly_payment);
        tvTotalPayment = findViewById(R.id.tv_total_payment);
        tvTotalInterest = findViewById(R.id.tv_total_interest);
        cbTaxes = findViewById(R.id.cb_taxes);
        cbInsurance = findViewById(R.id.cb_insurance);
        spLoanType = findViewById(R.id.sp_loan_type);
        btnCalculate = findViewById(R.id.btn_calculate);

        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
                R.array.loan_types, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spLoanType.setAdapter(adapter);
        spLoanType.setOnItemSelectedListener(this);

        etLoanAmount.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                if (!s.toString().equals("")) {
                    loanAmount = Double.parseDouble(s.toString());
                } else {
                    loanAmount = 0;
                }
            }

            @Override
            public void afterTextChanged(Editable s) {}
        });

        etLoanTerm.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                if (!s.toString().equals("")) {
                    loanTerm = Integer.parseInt(s.toString());
                } else {
                    loanTerm = 0;
                }
            }

            @Override
            public void afterTextChanged(Editable s) {}
        });

        etInterestRate.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                if (!s.toString().equals("")) {
                    interestRate = Double.parseDouble(s.toString());
                } else {
                    interestRate = 0;
                }
            }

            @Override
            public void afterTextChanged(Editable s) {}
        });

        cbTaxes.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                taxes = cbTaxes.isChecked();
            }
        });

        cbInsurance.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                insurance = cbInsurance.isChecked();
            }
        });

        btnCalculate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch (loanType) {
                    case 0:
                        calculateEqualPrincipal();
                        break;
                    case 1:
                        calculateEqualInstallment();
                        break;
                    case 2:
                        calculateReverseEqualPrincipal();
                        break;
                    case 3:
                        calculateReverseEqualInstallment();
                        break;
                }
                tvMonthlyPayment.setText(df.format(monthlyPayment));
                tvTotalPayment.setText(df.format(totalPayment));
                tvTotalInterest.setText(df.format(totalInterest));
            }
        });
    }

    private void calculateEqualPrincipal() {
        double monthlyInterestRate = interestRate / 12;
        double principal = loanAmount / loanTerm;
        double interest = loanAmount * monthlyInterestRate;
        monthlyPayment = principal + interest;
        totalPayment = monthlyPayment * loanTerm;
        totalInterest = totalPayment - loanAmount;
        if (taxes) {
            totalPayment += loanTerm * 100;
        }
        if (insurance) {
            totalPayment += loanTerm * 50;
        }
    }

    private void calculateEqualInstallment() {
        double monthlyInterestRate = interestRate / 12;
        double monthlyPaymentRate = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTerm)
                / (Math.pow(1 + monthlyInterestRate, loanTerm) - 1);
        monthlyPayment = loanAmount * monthlyPaymentRate;
        totalPayment = monthlyPayment * loanTerm;
        totalInterest = totalPayment - loanAmount;
        if (taxes) {
            totalPayment += loanTerm * 100;
        }
        if (insurance) {
            totalPayment += loanTerm * 50;
        }
    }

    private void calculateReverseEqualPrincipal() {
        double monthlyInterestRate = interestRate / 12;
        double principal = loanAmount / loanTerm;
        double interest = loanAmount * monthlyInterestRate;
        double monthlyPayment1 = principal + interest;
        double monthlyPayment2 = monthlyPayment1 + principal * monthlyInterestRate;
        double monthlyPayment3 = monthlyPayment2 + principal * monthlyInterestRate;
        double monthlyPayment4 = monthlyPayment3 + principal * monthlyInterestRate;
        double monthlyPayment5 = monthlyPayment4 + principal * monthlyInterestRate;
        double monthlyPayment6 = monthlyPayment5 + principal * monthlyInterestRate;
        double monthlyPayment7 = monthlyPayment6 + principal * monthlyInterestRate;
        double monthlyPayment8 = monthlyPayment7 + principal * monthlyInterestRate;
        double monthlyPayment9 = monthlyPayment8 + principal * monthlyInterestRate;
        double monthlyPayment10 = monthlyPayment9 + principal * monthlyInterestRate;
        double monthlyPayment11 = monthlyPayment10 + principal * monthlyInterestRate;
        double monthlyPayment12 = monthlyPayment11 + principal * monthlyInterestRate;
        monthlyPayment = (monthlyPayment1 + monthlyPayment2 + monthlyPayment3 + monthlyPayment4
                + monthlyPayment5 + monthlyPayment6 + monthlyPayment7 + monthlyPayment8
                + monthlyPayment9 + monthlyPayment10 + monthlyPayment11 + monthlyPayment12) / 12;
        totalPayment = monthlyPayment * loanTerm;
        totalInterest = totalPayment - loanAmount;
        if (taxes) {
            totalPayment += loanTerm * 100;
        }
        if (insurance) {
            totalPayment += loanTerm * 50;
        }
    }

    private void calculateReverseEqualInstallment() {
        double monthlyInterestRate = interestRate / 12;
        double monthlyPaymentRate = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTerm)
                / (Math.pow(1 + monthlyInterestRate, loanTerm) - 1);
        double monthlyPayment1 = loanAmount * monthlyPaymentRate;
        double monthlyPayment2 = (loanAmount - monthlyPayment1) * monthlyInterestRate + monthlyPayment1;
        double monthlyPayment3 = (loanAmount - monthlyPayment1 - monthlyPayment2) * monthlyInterestRate + monthlyPayment2;
        double monthlyPayment4 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3) * monthlyInterestRate + monthlyPayment3;
        double monthlyPayment5 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4) * monthlyInterestRate + monthlyPayment4;
        double monthlyPayment6 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5) * monthlyInterestRate + monthlyPayment5;
        double monthlyPayment7 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6) * monthlyInterestRate + monthlyPayment6;
        double monthlyPayment8 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6 - monthlyPayment7) * monthlyInterestRate + monthlyPayment7;
        double monthlyPayment9 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6 - monthlyPayment7 - monthlyPayment8) * monthlyInterestRate + monthlyPayment8;
        double monthlyPayment10 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6 - monthlyPayment7 - monthlyPayment8 - monthlyPayment9) * monthlyInterestRate + monthlyPayment9;
        double monthlyPayment11 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6 - monthlyPayment7 - monthlyPayment8 - monthlyPayment9 - monthlyPayment10) * monthlyInterestRate + monthlyPayment10;
        double monthlyPayment12 = (loanAmount - monthlyPayment1 - monthlyPayment2 - monthlyPayment3 - monthlyPayment4 - monthlyPayment5 - monthlyPayment6 - monthlyPayment7 - monthlyPayment8 - monthlyPayment9 - monthlyPayment10 - monthlyPayment11) * monthlyInterestRate + monthlyPayment11;
        monthlyPayment = (monthlyPayment1 + monthlyPayment2 + monthlyPayment3 + monthlyPayment4
                + monthlyPayment5 + monthlyPayment6 + monthlyPayment7 + monthlyPayment8
                + monthlyPayment9 + monthlyPayment10 + monthlyPayment11 + monthlyPayment12) / 12;
        totalPayment = monthlyPayment * loanTerm;
        totalInterest = totalPayment - loanAmount;
        if (taxes) {
            totalPayment += loanTerm * 100;
        }
        if (insurance) {
            totalPayment += loanTerm * 50;
        }
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        loanType = position;
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {}

}