安卓房贷计算器

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:focusable="true"
android:focusableInTouchMode="true"
android:orientation="vertical"
android:padding="5dp" >

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <TextView
                android:id="@+id/tv_price"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="购房总价："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <EditText
                android:id="@+id/et_price"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginBottom="5dp"
                android:layout_marginTop="5dp"
                android:layout_toLeftOf="@+id/tv_unit"
                android:layout_toRightOf="@+id/tv_price"
                android:background="@drawable/edit_selector"
                android:gravity="right|center"
                android:hint="请输入购房总价（单位万）"
                android:inputType="number"
                android:maxLength="4"
                android:textColor="@color/black"
                android:textColorHint="#cccccc"
                android:textSize="17sp" />

            <TextView
                android:id="@+id/tv_unit"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentRight="true"
                android:gravity="center"
                android:text="　万"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <TextView
                android:id="@+id/tv_part"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="按揭部分："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <EditText
                android:id="@+id/et_loan"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginBottom="5dp"
                android:layout_marginTop="5dp"
                android:layout_toLeftOf="@+id/tv_percent"
                android:layout_toRightOf="@+id/tv_part"
                android:background="@drawable/edit_selector"
                android:gravity="right|center"
                android:hint="请输入按揭百分比"
                android:inputType="number"
                android:maxLength="2"
                android:textColor="@color/black"
                android:textColorHint="#cccccc"
                android:textSize="17sp" />

            <TextView
                android:id="@+id/tv_percent"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentRight="true"
                android:gravity="center"
                android:text="　％"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </RelativeLayout>

        <Button
            android:id="@+id/btn_loan"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="计算贷款总额"
            android:textColor="@color/black"
            android:textSize="17sp" />

        <TextView
            android:id="@+id/tv_loan"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="5dp"
            android:text="其中贷款部分为：***万"
            android:textColor="@color/black"
            android:textSize="17sp" />

        <RadioGroup
            android:id="@+id/rg_payment"
            android:layout_width="match_parent"
            android:layout_height="45dp"
            android:orientation="horizontal" >

            <TextView
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:gravity="center"
                android:text="还款方式："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <RadioButton
                android:id="@+id/rb_interest"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:checked="true"
                android:gravity="left|center"
                android:text="等额本息"
                android:textColor="@color/black"
                android:textSize="17sp" />

            <RadioButton
                android:id="@+id/rb_principal"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:checked="false"
                android:gravity="left|center"
                android:text="等额本金"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </RadioGroup>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <CheckBox
                android:id="@+id/ck_business"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:button="@drawable/checkbox_selector"
                android:checked="true"
                android:gravity="center"
                android:text="商贷：　"
                android:textColor="@color/black"
                android:textSize="17sp" />

            <EditText
                android:id="@+id/et_business"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginBottom="5dp"
                android:layout_marginTop="5dp"
                android:layout_toLeftOf="@+id/tv_business_unit"
                android:layout_toRightOf="@+id/ck_business"
                android:background="@drawable/edit_selector"
                android:gravity="right|center"
                android:hint="请输入商业贷款总额（单位万）"
                android:inputType="number"
                android:maxLength="4"
                android:textColor="@color/black"
                android:textColorHint="#cccccc"
                android:textSize="17sp" />

            <TextView
                android:id="@+id/tv_business_unit"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentRight="true"
                android:gravity="center"
                android:text="　万"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <CheckBox
                android:id="@+id/ck_accumulation"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:button="@drawable/checkbox_selector"
                android:checked="false"
                android:gravity="center"
                android:text="公积金："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <EditText
                android:id="@+id/et_accumulation"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginBottom="5dp"
                android:layout_marginTop="5dp"
                android:layout_toLeftOf="@+id/tv_accumulation_unit"
                android:layout_toRightOf="@+id/ck_accumulation"
                android:background="@drawable/edit_selector"
                android:gravity="right|center"
                android:hint="请输入公积金贷款总额（单位万）"
                android:inputType="number"
                android:maxLength="4"
                android:textColor="@color/black"
                android:textColorHint="#cccccc"
                android:textSize="17sp" />

            <TextView
                android:id="@+id/tv_accumulation_unit"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentRight="true"
                android:gravity="center"
                android:text="　万"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <TextView
                android:id="@+id/tv_year"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentLeft="true"
                android:gravity="center"
                android:text="贷款年限："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <Spinner
                android:id="@+id/sp_year"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_toRightOf="@+id/tv_year"
                android:gravity="left|center"
                android:spinnerMode="dialog" />
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="45dp" >

            <TextView
                android:id="@+id/tv_ratio"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_alignParentLeft="true"
                android:gravity="center"
                android:text="基准利率："
                android:textColor="@color/black"
                android:textSize="17sp" />

            <Spinner
                android:id="@+id/sp_ratio"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_toRightOf="@+id/tv_ratio"
                android:gravity="left|center"
                android:spinnerMode="dialog" />
        </RelativeLayout>

        <Button
            android:id="@+id/btn_calculate"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="计算还款明细"
            android:textColor="@color/black"
            android:textSize="17sp" />

        <TextView
            android:id="@+id/tv_payment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="5dp"
            android:text="还款总额为：***万\n其中利息总额为：***万\n月供(每月还款额)为：***"
            android:textColor="@color/black"
            android:textSize="17sp" />
    </LinearLayout>
</ScrollView>

</LinearLayout>

import java.math.BigDecimal;
import java.math.RoundingMode;

import com.example.myapplication.util.Repayment;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.Toast;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Spinner;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

/**
 * Created by ouyangshen on 2017/9/24.
 */
@SuppressLint("DefaultLocale")
public class MortgageActivity extends AppCompatActivity implements OnClickListener,
        RadioGroup.OnCheckedChangeListener, OnCheckedChangeListener {
    private EditText et_price; // 声明一个编辑框对象
    private EditText et_loan; // 声明一个编辑框对象
    private TextView tv_loan; // 声明一个文本视图对象
    private RadioGroup rg_payment; // 声明一个单选组对象
    private CheckBox ck_business; // 声明一个复选框对象
    private EditText et_business; // 声明一个编辑框对象
    private CheckBox ck_accumulation; // 声明一个复选框对象
    private EditText et_accumulation; // 声明一个编辑框对象
    private TextView tv_payment; // 声明一个文本视图对象

    private boolean isInterest = true; // 是否为等额本息
    private boolean hasBusiness = true; // 是否存在商业贷款
    private boolean hasAccumulation = false; // 是否存在公积金贷款
    private int mYear; // 还款年限
    private double mBusinessRatio; // 商业贷款的利率
    private double mAccumulationRatio; // 公积金贷款的利率

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

        et_price = findViewById(R.id.et_price);
        et_loan = findViewById(R.id.et_loan);
        tv_loan = findViewById(R.id.tv_loan);
        rg_payment = findViewById(R.id.rg_payment);
        rg_payment.setOnCheckedChangeListener(this);
        ck_business = findViewById(R.id.ck_business);
        ck_business.setOnCheckedChangeListener(this);
        et_business = findViewById(R.id.et_business);
        ck_accumulation = findViewById(R.id.ck_accumulation);
        ck_accumulation.setOnCheckedChangeListener(this);
        et_accumulation = findViewById(R.id.et_accumulation);
        tv_payment = findViewById(R.id.tv_payment);
        findViewById(R.id.btn_loan).setOnClickListener(this);
        findViewById(R.id.btn_calculate).setOnClickListener(this);
        initYearSpinner();
        initRatioSpinner();
    }

    // 初始化贷款年限下拉框
    private void initYearSpinner() {
        ArrayAdapter<String> yearAdapter = new ArrayAdapter<String>(this,
                R.layout.item_select, yearDescArray);
        yearAdapter.setDropDownViewResource(R.layout.item_dropdown);
        Spinner sp_year = findViewById(R.id.sp_year);
        sp_year.setPrompt("请选择贷款年限");
        sp_year.setAdapter(yearAdapter);
        sp_year.setSelection(0);
        sp_year.setOnItemSelectedListener(new YearSelectedListener());
    }

    private String[] yearDescArray = {"5年", "10年", "15年", "20年", "30年"};
    private int[] yearArray = {5, 10, 15, 20, 30};

    // 定义一个贷款年限的选择监听器
    class YearSelectedListener implements OnItemSelectedListener {
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
            mYear = yearArray[arg2];
        }

        public void onNothingSelected(AdapterView<?> arg0) {}
    }

    // 初始化基准利率下拉框
    private void initRatioSpinner() {
        ArrayAdapter<String> ratioAdapter = new ArrayAdapter<String>(this,
                R.layout.item_select, ratioDescArray);
        ratioAdapter.setDropDownViewResource(R.layout.item_dropdown);
        Spinner sp_ratio = findViewById(R.id.sp_ratio);
        sp_ratio.setPrompt("请选择基准利率");
        sp_ratio.setAdapter(ratioAdapter);
        sp_ratio.setSelection(0);
        sp_ratio.setOnItemSelectedListener(new RatioSelectedListener());
    }

    private String[] ratioDescArray = {
            "2015年10月24日 五年期商贷利率 4.90%　公积金利率 3.25%",
            "2015年08月26日 五年期商贷利率 5.15%　公积金利率 3.25%",
            "2015年06月28日 五年期商贷利率 5.40%　公积金利率 3.50%",
            "2015年05月11日 五年期商贷利率 5.65%　公积金利率 3.75%",
            "2015年03月01日 五年期商贷利率 5.90%　公积金利率 4.00%",
            "2014年11月22日 五年期商贷利率 6.15%　公积金利率 4.25%",
            "2012年07月06日 五年期商贷利率 6.15%　公积金利率 4.50%",
    };
    private double[] businessArray = {4.90, 5.15, 5.40, 5.65, 5.90, 6.15, 6.55};
    private double[] accumulationArray = {3.25, 3.25, 3.50, 3.75, 4.00, 4.25, 4.50};

    // 定义一个基准利率的选择监听器
    class RatioSelectedListener implements OnItemSelectedListener {
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
            mBusinessRatio = businessArray[arg2];
            mAccumulationRatio = accumulationArray[arg2];
        }

        public void onNothingSelected(AdapterView<?> arg0) {}
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.btn_loan) { // 点击了按钮“计算贷款总额”
            if (TextUtils.isEmpty(et_price.getText().toString())) {
                Toast.makeText(this, "购房总价不能为空", Toast.LENGTH_SHORT).show();
                return;
            }
            if (TextUtils.isEmpty(et_loan.getText().toString())) {
                Toast.makeText(this, "按揭部分不能为空", Toast.LENGTH_SHORT).show();
                return;
            }
            showLoan(); // 显示计算好的贷款总额
        } else if (v.getId() == R.id.btn_calculate) { // 点击了按钮“计算还款明细”
            if (hasBusiness && TextUtils.isEmpty(et_business.getText().toString())) {
                Toast.makeText(this, "商业贷款总额不能为空", Toast.LENGTH_SHORT).show();
                return;
            }
            if (hasAccumulation && TextUtils.isEmpty(et_accumulation.getText().toString())) {
                Toast.makeText(this, "公积金贷款总额不能为空", Toast.LENGTH_SHORT).show();
                return;
            }
            if (!hasBusiness && !hasAccumulation) {
                Toast.makeText(this, "请选择商业贷款或者公积金贷款", Toast.LENGTH_SHORT).show();
                return;
            }
            showRepayment(); // 显示计算好的还款明细
        }
    }

    // 根据购房总价和按揭比例，计算贷款总额
    private void showLoan() {
        double total = Double.parseDouble(et_price.getText().toString());
        double rate = Double.parseDouble(et_loan.getText().toString()) / 100;
        String desc = String.format("您的贷款总额为%s万元", formatDecimal(total * rate, 2));
        tv_loan.setText(desc);
    }

    // 根据贷款的相关条件，计算还款总额、利息总额，以及月供
    private void showRepayment() {
        Repayment businessResult = new Repayment();
        Repayment accumulationResult = new Repayment();
        if (hasBusiness) { // 申请了商业贷款
            double businessLoad = Double.parseDouble(et_business.getText().toString()) * 10000;
            double businessTime = mYear * 12;
            double businessRate = mBusinessRatio / 100;
            // 计算商业贷款部分的还款明细
            businessResult = calMortgage(businessLoad, businessTime, businessRate, isInterest);
        }
        if (hasAccumulation) { // 申请了公积金贷款
            double accumulationLoad = Double.parseDouble(et_accumulation.getText().toString()) * 10000;
            double accumulationTime = mYear * 12;
            double accumulationRate = mAccumulationRatio / 100;
            // 计算公积金贷款部分的还款明细
            accumulationResult = calMortgage(accumulationLoad, accumulationTime, accumulationRate, isInterest);
        }
        String desc = String.format("您的贷款总额为%s万元", formatDecimal(
                (businessResult.mTotal + accumulationResult.mTotal) / 10000, 2));
        desc = String.format("%s\n　　还款总额为%s万元", desc, formatDecimal(
                (businessResult.mTotal + businessResult.mTotalInterest +
                        accumulationResult.mTotal + accumulationResult.mTotalInterest) / 10000, 2));
        desc = String.format("%s\n其中利息总额为%s万元", desc, formatDecimal(
                (businessResult.mTotalInterest + accumulationResult.mTotalInterest) / 10000, 2));
        desc = String.format("%s\n　　还款总时间为%d月", desc, mYear * 12);
        if (isInterest) { // 如果是等额本息方式
            desc = String.format("%s\n每月还款金额为%s元", desc, formatDecimal(
                    businessResult.mMonthRepayment + accumulationResult.mMonthRepayment, 2));
        } else { // 如果是等额本金方式
            desc = String.format("%s\n首月还款金额为%s元，其后每月递减%s元", desc, formatDecimal(
                    businessResult.mMonthRepayment + accumulationResult.mMonthRepayment, 2),
                    formatDecimal(businessResult.mMonthMinus + accumulationResult.mMonthMinus, 2));
        }
        tv_payment.setText(desc);
    }

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        if (checkedId == R.id.rb_interest) { // 选择了等额本息方式
            isInterest = true;
        } else if (checkedId == R.id.rb_principal) { // 选择了等额本金方式
            isInterest = false;
        }
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        if (buttonView.getId() == R.id.ck_business) { // 勾选了商业贷款
            hasBusiness = isChecked;
        } else if (buttonView.getId() == R.id.ck_accumulation) { // 勾选了公积金贷款
            hasAccumulation = isChecked;
        }
    }

    // 精确到小数点后第几位
    private String formatDecimal(double value, int digit) {
        BigDecimal bd = new BigDecimal(value);
        bd = bd.setScale(digit, RoundingMode.HALF_UP);
        return bd.toString();
    }

    // 根据贷款金额、还款年限、基准利率，计算还款信息
    private Repayment calMortgage(double ze, double nx, double rate, boolean bInterest) {
        double zem = (ze * rate / 12 * Math.pow((1 + rate / 12), nx))
                / (Math.pow((1 + rate / 12), nx) - 1);
        double amount = zem * nx;
        double rateAmount = amount - ze;

        double benjinm = ze / nx;
        double lixim = ze * (rate / 12);
        double diff = benjinm * (rate / 12);
        double huankuanm = benjinm + lixim;
        double zuihoukuan = diff + benjinm;
        double av = (huankuanm + zuihoukuan) / 2;
        double zong = av * nx;
        double zongli = zong - ze;

        Repayment result = new Repayment();
        result.mTotal = ze;
        if (bInterest) {
            result.mMonthRepayment = zem;
            result.mTotalInterest = rateAmount;
        } else {
            result.mMonthRepayment = huankuanm;
            result.mMonthMinus = diff;
            result.mTotalInterest = zongli;
        }
        return result;
    }

}

public class Repayment {
    public double mTotal;
    public double mMonthRepayment;
    public double mMonthMinus;
    public double mTotalInterest;
    public Repayment() {
        mTotal = 0;
        mMonthRepayment = 0;
        mMonthMinus = 0;
        mTotalInterest = 0;
    }
}