Question

之前我曾问过几个问题，但我决定回到基础。

我正在创建一个maths android应用程序，每个页面有三个TextField s，用户可以输入一个数字，我已经将这些TextField解析为一个double。但是，假设用户在TextField中输入了一个数字，我希望程序告诉我第三个文本字段的值。

目前我可以让程序运行一个计算，但是当我为剩下的两个TextField添加if语句时，程序在我点击计算时崩溃了。该程序背后的关键是发现哪个TextField为空，以便程序可以进行正确的计算。

我目前正在尝试.getText().toString().isEmpty()，但这不起作用，我也尝试过.length（）== 0，但这也不起作用。

当我运行模拟器并单击计算器按钮时，程序会在我添加更多变量时崩溃，但只需一次计算即可。

任何人都可以帮我弄清楚为什么If语句不起作用，如果可能，任何人都可以提供解决方案吗？

很抱歉，如果我的格式化已关闭，我对Java相对较新，下面是Java

Button calc1 = (Button) findViewById(R.id.current_calculate);

    calc1.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {

            EditText Charge1 = (EditText) findViewById(R.id.number_input_2);
            EditText Time1 = (EditText) findViewById(R.id.number_input_3);
            EditText current1 = (EditText) findViewById(R.id.number_input_1);
            TextView Distances_answer = (TextView) findViewById(R.id.Distances_answer);
            double charge = Double
                    .parseDouble(Charge1.getText().toString());
            double time = Double.parseDouble(Time1.getText().toString());
            double current = Double.parseDouble(current1.getText()
                    .toString());
            // Time is a class in Java
            if (current1.getText().toString().isEmpty()) {
                Distances_answer.setText("" + charge * time);

            } else if (Time1.length() == 0) {

                Distances_answer.setText(" " + charge / current);
            }

        }
    });

我还提供了XML，以备需要时使用

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/background1"
android:gravity="fill"
android:orientation="vertical"
android:textColor="#ffffff"
tools:context=".CurrentPage" >

<TextView
    android:id="@+id/Current_hint"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    android:layout_marginTop="33dp"
    android:text="Welcome to the Current Calculation page.
     Hint - Use the check boxes to find the values that are missing "
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:textColor="#ffffff"
    tools:ignore="HardcodedText" />

<TextView
    android:id="@+id/Equation_letter"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/current_calculate"
    android:layout_marginTop="37dp"
    android:layout_toLeftOf="@+id/current_calculate"
    android:text="     HELLO  "
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffffff"
    tools:ignore="HardcodedText" />

<TextView
    android:id="@+id/Distances_answer"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/Equation_letter"
    android:layout_alignBottom="@+id/Equation_letter"
    android:layout_alignLeft="@+id/current_calculate"
    android:layout_alignParentRight="true"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffffff" />

<TextView
    android:id="@+id/t"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/Q"
    android:layout_alignRight="@+id/Q"
    android:layout_below="@+id/Q"
    android:layout_marginTop="36dp"
    android:gravity="right|top"
    android:text="t ="
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffffff"
    tools:ignore="HardcodedText" />

<CheckBox
    android:id="@+id/custom3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/t"
    android:layout_alignLeft="@+id/custom2"
    android:background="@drawable/check_box_new"
    android:button="@drawable/check_box_new" />

<CheckBox
    android:id="@+id/custom1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/number_input_3"
    android:layout_alignLeft="@+id/custom3"
    android:background="@drawable/check_box_new"
    android:button="@drawable/check_box_new" />

<ScrollView
    android:id="@+id/scrollView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/Current_hint"
    android:layout_alignRight="@+id/Current_hint"
    android:layout_below="@+id/Equation_letter"
    android:layout_marginTop="25dp" >

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

        <TextView
            android:id="@+id/CurrentmainHelp"
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="1.31"
            android:text="HELP! This equation can be used to calculate the current of an object in amps. The correct equation to discover amps is I=Q/t. Where I = current, Q = charge flowing past a point in the circuit, and t = time taken for the charge to flow. Please note, Q is measure in coulombs and t is measured in seconds, with I being measured in amperes.

    Still need more help? "
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:textSize="18sp"
            tools:ignore="HardcodedText" />

        <Button
            android:id="@+id/Yes_Please"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginBottom="36dp"
            android:layout_weight="1.31"
            android:onClick="CurrentHelp"
            android:text="Yes Please"
            android:textColor="#ffffff" />
    </LinearLayout>
</ScrollView>

<Button
    android:id="@+id/current_calculate"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="@string/Calculate_Current"
    android:textColor="#ffffff" />

<EditText
    android:id="@+id/number_input_2"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/t"
    android:layout_alignLeft="@+id/number_input_1"
    android:layout_alignRight="@+id/number_input_1"
    android:ems="10"
    android:focusable="true"
    android:inputType="numberDecimal"
    android:textColor="#ffffff" >

    <requestFocus />
</EditText>

<EditText
    android:id="@+id/number_input_3"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/t"
    android:layout_alignLeft="@+id/number_input_2"
    android:layout_alignRight="@+id/number_input_2"
    android:ems="10"
    android:focusable="true"
    android:inputType="numberDecimal"
    android:textColor="#ffffff" />

<CheckBox
    android:id="@+id/custom2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/number_input_1"
    android:layout_marginLeft="45dp"
    android:layout_toRightOf="@+id/number_input_1"
    android:background="@drawable/check_box_new"
    android:button="@drawable/check_box_new" />

<EditText
    android:id="@+id/number_input_1"
    android:layout_width="150dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/Q"
    android:layout_alignRight="@+id/current_calculate"
    android:ems="10"
    android:focusable="true"
    android:inputType="numberDecimal"
    android:singleLine="true"
    android:textColor="#ffffff" />

<TextView
    android:id="@+id/Q"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/Equation_letter"
    android:layout_below="@+id/I"
    android:layout_marginTop="36dp"
    android:gravity="right|top"
    android:text="Q ="
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffffff"
    tools:ignore="HardcodedText" />

<TextView
    android:id="@+id/I"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/Q"
    android:layout_alignRight="@+id/Q"
    android:layout_below="@+id/Current_hint"
    android:layout_marginTop="65dp"
    android:gravity="right|top"
    android:text="I ="
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffffff"
    tools:ignore="HardcodedText" />

Answer 1

我认为应用程序崩溃是因为您正在解析EditText到double的内容，即使它们可能为空。 Double.parseDouble函数如果无法解析给定NumberFormatException中的double，则会抛出String。要解决此问题，请在尝试解析之前执行空字符串检查，或捕获异常。

例如：

double charge = 0.0; // some default value
if (!Charge1.getText().toString().isEmpty()) {
    charge = Double.parseDouble(Charge1.getText().toString());
}

double time = 0.0; // some default value
if (!Time1.getText().toString().isEmpty()) {
    time = Double.parseDouble(Time1.getText().toString());
}

double current = 0.0; // some default value
if (!current1.getText().toString().isEmpty()) {
    current = Double.parseDouble(current1.getText().toString());
}

如果声明强制程序崩溃

1 个答案: