将总计与编辑文本输出相加并防止出现负数

Question

遗憾的是，在一个简单的数学问题上，我被困住了。 我正在创建一个咖啡应用程序，如下所示，它取“数量”并将其乘以价格以创建每个饮料饮料的小计。然后它将从饮料中取出所有小计，并将它们一起添加到底部的输出中，这将自动更新。

我已经处理了从0添加或减去的代码（我仍然无法找到防止它低于0的方法，如果有人有想法，请帮助我们）。 我有它，所以前两个按钮（粉红色）现在适用于Espresso和Macchiato。

这是我的Java文件

package com.example.cofeeshop;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;


public class DrinkMenu extends Activity {
EditText quantity, quantity2, total;

Button button, plus1, minus1, plus2, minus2;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.drinkmenu);
    addListenerOnButton();

    // area for the espresso
    plus1 = (Button) findViewById(R.id.button6);
    minus1 = (Button) findViewById(R.id.button7);
    quantity = (EditText) findViewById(R.id.editText2);

    // area for the macchiato
    plus2 = (Button) findViewById(R.id.button8);
    minus2 = (Button) findViewById(R.id.button9);
    quantity2 = (EditText) findViewById(R.id.editText4);

    //subtotal for espresso
    //subtotal for macchiato

    total = (EditText) findViewById(R.id.editText9);

    plus1.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View V){

            String numb1 = quantity.getText().toString();

            int num1 = Integer.parseInt(numb1);
            int inum1 = num1+1;
            quantity.setText(Integer.toString(inum1));
        }
    });//plus1 button
    minus1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            String numb1 = quantity.getText().toString();
            int num1 = Integer.parseInt(numb1);
            int inum1 = num1-1;
            quantity.setText(Integer.toString(inum1));

        }
    });//minus1 button

    plus2.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View V){

            String numb2 = quantity2.getText().toString();

            int num2 = Integer.parseInt(numb2);
            int inum2 = num2+1;
            quantity2.setText(Integer.toString(inum2));
        }
    });//plus2 button
    minus2.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            String numb2 = quantity2.getText().toString();
            int num2 = Integer.parseInt(numb2);
            int inum2 = num2-1;
            quantity2.setText(Integer.toString(inum2));

        }
    });//minus2 button
    // Here is where I think I should place the sub-total multiplied by the prices
    // and will be out put to the total = espresso_sub_total*espress_price + 
    // macchiato_sub_total*macchiato_price + and so on for the other drinks

  }

}

现在，我可能必须将总价格设置为文本视图，而不是编辑文本，想法？

因此，在实施了来自用户@ useruser3249477和@Shobhit的想法之后，我已经让数字停止在0以下和10以上，但后来我尝试在总面积'0'中一起添加总数。我已经为java和xml文件更新了下面的代码。当我按下“+”按钮时它会崩溃。

更新的Java源代码：

package com.example.cofeeshop;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class DrinkMenu extends Activity {
EditText quantity, quantity2;
//TextView total;
Button button, plus1, minus1, plus2, minus2;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.drinkmenu);
    addListenerOnButton();

    // area for the espresso
    plus1 = (Button) findViewById(R.id.button6);
    minus1 = (Button) findViewById(R.id.button7);
    quantity = (EditText) findViewById(R.id.editText2);

    // area for the macchiato
    plus2 = (Button) findViewById(R.id.button8);
    minus2 = (Button) findViewById(R.id.button9);
    quantity2 = (EditText) findViewById(R.id.editText4);

    //espresso-sub-total
    //macchiato-sub-total

    //total = (TextView) findViewById(R.id.textView7);


    plus1.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View V){

            String numb1 = quantity.getText().toString();

            int num1 = Integer.parseInt(numb1);
            int inum1 = num1+1;
            if (inum1 > 10) return;
            quantity.setText(Integer.toString(inum1));
        }
    });//plus1 button
    minus1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            String numb1 = quantity.getText().toString();
            int num1 = Integer.parseInt(numb1);
            int inum1 = num1-1;
            if (inum1 < 0) return;
            quantity.setText(Integer.toString(inum1));

        }
    });//minus2 button

    plus2.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View V){

            String numb2 = quantity2.getText().toString();

            int num2 = Integer.parseInt(numb2);
            int inum2 = num2+1;
            if (inum2 > 10) return;
            quantity2.setText(Integer.toString(inum2));
        }
    });//plus1 buttons
    minus2.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            String numb2 = quantity2.getText().toString();
            int num2 = Integer.parseInt(numb2);
            int inum2 = num2-1;
            if (inum2 < 0) return;
            quantity2.setText(Integer.toString(inum2));

        }
    });

//    double subtotal = Double.parseDouble(numb1);
    // Here is where I think I should place the sub-total multiplied by the prices
    // and will be out put to the total = num1*3;


    final TextView total = (TextView) findViewById(R.id.textView7);
    TextWatcher textWatcher = new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
            // Remove previous price of these items
            int count = Integer.parseInt(charSequence.toString());
            // Assume total holds text of an integer
            int curTotal = Integer.parseInt(total.getText().toString());
            int newTotal = curTotal - count*3;
            total.setText(newTotal);
        }

        @Override
        public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
            // Add the new items price
            int count = Integer.parseInt(charSequence.toString());
            // Assume total holds text of an integer
            int curTotal = Integer.parseInt(total.getText().toString());
            int newTotal = curTotal + count*3;
            total.setText(newTotal);
        }

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

    quantity.addTextChangedListener(textWatcher);
    quantity2.addTextChangedListener(textWatcher);
}
//order button code that is useless to this question.
}

以下是我更新的更新后的XML文件：          

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignEnd="@+id/button"
    android:layout_alignParentTop="true"
    android:layout_alignRight="@+id/button"
    android:layout_marginRight="75dp"
    android:layout_toLeftOf="@+id/textView2"
    android:layout_toStartOf="@+id/textView2"
    android:background="#FFFFFF"
    android:text="Drinks:"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textSize="24dp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignEnd="@+id/orderbtn"
    android:layout_alignParentTop="true"
    android:layout_alignRight="@+id/orderbtn"
    android:background="#FFFFFF"
    android:text="Quantity:"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textSize="24dp"
    android:textStyle="bold" />

<Button
    android:id="@+id/button"
    android:layout_width="240dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/textView"
    android:layout_marginTop="30dp"
    android:background="#FFFFFF"
    android:text="Espresso"
    android:textSize="24dp" />

<Button
    android:id="@+id/button2"
    android:layout_width="240dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/button"
    android:layout_marginTop="30dp"
    android:background="#FFFFFF"
    android:text="Macchiato"
    android:textSize="24dp" />

<Button
    android:id="@+id/button3"
    android:layout_width="240dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/button2"
    android:layout_marginTop="30dp"
    android:background="#FFFFFF"
    android:text="Con Panna"
    android:textSize="24dp" />

<Button
    android:id="@+id/button5"
    style="?android:attr/buttonStyleSmall"
    android:layout_width="240dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/button4"
    android:layout_marginTop="30dp"
    android:background="#FFFFFF"
    android:text="Latte"
    android:textSize="24dp" />

<Button
    android:id="@+id/button6"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignParentEnd="true"
    android:layout_alignParentRight="true"
    android:layout_alignTop="@+id/button"
    android:background="#ffff45df"
    android:text="+"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText2"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button2"
    android:layout_alignTop="@+id/button"
    android:layout_toLeftOf="@+id/button6"
    android:layout_toStartOf="@+id/button6"
    android:background="#FFFFFF"
    android:digits="0123456789"
    android:ems="10"
    android:inputType="number"
    android:text="0"
    android:textSize="24dp" />

<Button
    android:id="@+id/button7"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button"
    android:layout_toLeftOf="@+id/editText2"
    android:layout_toStartOf="@+id/editText2"
    android:background="#ffff45df"
    android:text="-"
    android:textSize="24dp" />

<Button
    android:id="@+id/button8"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignParentEnd="true"
    android:layout_alignParentRight="true"
    android:layout_alignTop="@+id/button2"
    android:background="#ffff45df"
    android:text="+"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText3"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button2"
    android:layout_toLeftOf="@+id/button8"
    android:layout_toStartOf="@+id/button8"
    android:background="#FFFFFF"
    android:ems="10"
    android:inputType="number"
    android:text=" 0"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText4"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/button8"
    android:layout_alignTop="@+id/button2"
    android:layout_toLeftOf="@+id/button8"
    android:layout_toStartOf="@+id/button8"
    android:background="#FFFFFF"
    android:digits="0123456789"
    android:ems="10"
    android:inputType="number"
    android:text="0"
    android:textSize="24sp" />

<Button
    android:id="@+id/button9"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button2"
    android:layout_toLeftOf="@+id/editText3"
    android:layout_toStartOf="@+id/editText3"
    android:background="#ffff45df"
    android:text="-"
    android:textSize="24dp" />

<Button
    android:id="@+id/button10"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignEnd="@+id/button8"
    android:layout_alignRight="@+id/button8"
    android:layout_alignTop="@+id/button3"
    android:background="#ffff45df"
    android:text="+"
    android:textSize="24dp" />

<Button
    android:id="@+id/button11"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignParentEnd="true"
    android:layout_alignParentRight="true"
    android:layout_alignTop="@+id/button4"
    android:background="#ffff45df"
    android:text="+"
    android:textSize="24dp" />

<Button
    android:id="@+id/button12"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignParentEnd="true"
    android:layout_alignParentRight="true"
    android:layout_alignTop="@+id/button5"
    android:background="#ffff45df"
    android:text="+"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText5"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button4"
    android:layout_alignTop="@+id/button3"
    android:layout_toLeftOf="@+id/button10"
    android:layout_toStartOf="@+id/button10"
    android:background="#FFFFFF"
    android:digits="0123456789"
    android:ems="10"
    android:inputType="number"
    android:text="0"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText6"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/button11"
    android:layout_alignTop="@+id/button4"
    android:layout_toLeftOf="@+id/button11"
    android:layout_toStartOf="@+id/button11"
    android:background="#FFFFFF"
    android:digits="0123456789"
    android:ems="10"
    android:inputType="number"
    android:text="0"
    android:textSize="24dp" />

<EditText
    android:id="@+id/editText7"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/button12"
    android:layout_alignTop="@+id/button5"
    android:layout_toLeftOf="@+id/button12"
    android:layout_toStartOf="@+id/button12"
    android:background="#FFFFFF"
    android:digits="0123456789"
    android:ems="10"
    android:inputType="number"
    android:text="0"
    android:textSize="24dp" />

<Button
    android:id="@+id/button14"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button4"
    android:layout_toLeftOf="@+id/editText6"
    android:layout_toStartOf="@+id/editText6"
    android:background="#ffff45df"
    android:text="-"
    android:textSize="24sp" />

<Button
    android:id="@+id/button15"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button5"
    android:layout_toLeftOf="@+id/editText7"
    android:layout_toStartOf="@+id/editText7"
    android:background="#ffff45df"
    android:text="-"
    android:textSize="24sp" />

<Button
    android:id="@+id/button16"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/button3"
    android:layout_toLeftOf="@+id/editText5"
    android:layout_toStartOf="@+id/editText5"
    android:background="#ffff45df"
    android:text="-"
    android:textSize="24sp" />

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button7"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="$3.00 per drink"
    android:textColor="#000000"
    android:textSize="20sp" />

<TextView
    android:id="@+id/textView3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button9"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="$3.00 per drink"
    android:textColor="#000000"
    android:textSize="20sp" />

<TextView
    android:id="@+id/textView4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button16"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="$3.00 per drink"
    android:textColor="#000000"
    android:textSize="20sp" />

<TextView
    android:id="@+id/textView5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button14"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="$3.00 per drink"
    android:textColor="#000000"
    android:textSize="20sp" />

<TextView
    android:id="@+id/textView6"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button15"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="$3.00 per drink"
    android:textColor="#000000"
    android:textSize="20sp" />

<Button
    android:id="@+id/button4"
    android:layout_width="240dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/button3"
    android:layout_marginTop="32dp"
    android:background="#FFFFFF"
    android:text="Americano"
    android:textSize="24dp"
    android:textColor="#000000" />

<Button
    android:id="@+id/orderbtn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true"
    android:layout_alignParentRight="true"
    android:background="@drawable/buttonround"
    android:text="Order"
    android:textSize="24sp" />

<TextView
    android:id="@+id/textView8"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/orderbtn"
    android:layout_alignBottom="@+id/orderbtn"
    android:layout_alignParentLeft="true"
    android:background="#FFFFFF"
    android:text="Total:  $"
    android:textColor="#000000"
    android:textSize="24sp" />

<TextView
    android:id="@+id/textView7"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/textView8"
    android:layout_alignBottom="@+id/textView8"
    android:layout_alignLeft="@+id/textView"
    android:layout_alignRight="@+id/textView6"
    android:layout_alignStart="@+id/textView"
    android:background="#FFFFFF"
    android:text="0"
    android:textSize="24sp" />

</RelativeLayout>

以下是一些错误。

E / AndroidRuntime（369）：致命异常：主

E / AndroidRuntime（369）：android.content.res.Resources $ NotFoundException：字符串资源ID＃0x0 //似乎在这里

E / AndroidRuntime（369）：在android.content.res.Resources.getText（Resources.java:201）

Answer 1

简单检查可以防止负值（使用按钮）：

minus2.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        String numb2 = quantity2.getText().toString();
        int num2 = Integer.parseInt(numb2);
        int inum2 = num2-1;
        if (inum2 < 0) return;
        quantity2.setText(Integer.toString(inum2));
    }
});

要防止手动输入负值，您可以将android:digits="0123456789"设置为@ShobhitPuri建议。

然后，您需要设置TextWatchers：

final EditText total = (EditText) findViewById(R.id.editText9);
    TextWatcher textWatcher = new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
            // Remove previous price of these items
            int count = Integer.parseInt(charSequence.toString());
            // Assume total holds text of an integer
            int curTotal = Integer.parseInt(total.getText().toString());
            int newTotal = curTotal - count*3;
            total.setText(newTotal);
        }

        @Override
        public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
            // Add the new items price
            int count = Integer.parseInt(charSequence.toString());
            // Assume total holds text of an integer
            int curTotal = Integer.parseInt(total.getText().toString());
            int newTotal = curTotal + count*3;
            total.setText(newTotal);
        }

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

// Now set the TextWatcher on every count EditText
// If you have different prices, you'll need multiple TextWatchers
quantity1.addTextChangedListener(textWatcher);
quantity2.addTextChangedListener(textWatcher);

...

Answer 2

  

“我仍然无法想办法防止它低于0”

• 您可以通过一种方式将android:digits="0123456789"添加到xml文件中的EditText。这将阻止用户输入除这些号码之外的任何内容。

• 另一种方法是检查onClickListener。在此，您需要使用EditText检查所有ed.getText()的值，然后检查其整数是否在您可接受的范围内。

• 另一种方法是在EditText上使用addTextChangedListener。你可以听你在那里输入什么。当小于0或者放入无效字符时，你可以检查条件。（最好限制键盘，以防止垃圾进入首位）。