基本计算器Android应用程序

我正在开发一个基本计算器android应用程序，我坚持在某个阶段。此应用程序从textview中获取输入并将其存储在一个数字中。基本计算器Android应用程序

从用户处获取第二个输入时出现问题。

我正在设置用于将第一个输入（第一个数字）为空的字符串。使用相同的字符串，我怎样才能使字符串为空，并允许定义操作后的第二个输入。那里的任何人都可以帮助我并感激我。

预先感谢您..

public class MainActivity extends AppCompatActivity { 

    String answer = ""; 
    float num1, num2; 
    int flag = 0; 
    String operation = ""; 
    TextView textViewAnswer; 
    Button buttonOne; 
    Button buttonTwo; 
    Button buttonThree; 
    Button buttonFour; 
    Button buttonFive; 
    Button buttonSix; 
    Button buttonSeven; 
    Button buttonEight; 
    Button buttonNine; 
    Button buttonZero; 
    Button buttonAddition; 
    Button buttonSubstraction; 
    Button buttonMultiplication; 
    Button buttonDivision; 
    Button buttonDot; 
    Button buttonEqual; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     textViewAnswer = (TextView) findViewById(R.id.textview_answer); 
    } 


    public void one(View view){ 
     buttonOne = (Button) findViewById(R.id.button_one); 

     if (flag == 1) { 
      num1 = Float.parseFloat(textViewAnswer.getText().toString()); 
      flag = 0; 
      answer = ""; 
     } 
     else { 
      checkLength(buttonOne); 
      textViewAnswer.setText(answer); 
     } 
    } 

    public void two(View view){ 
     buttonTwo = (Button) findViewById(R.id.button_two); 
     checkLength(buttonTwo); 
     textViewAnswer.setText(answer); 
     if (flag == 1) { 
      num1 = Float.parseFloat(textViewAnswer.getText().toString()); 
      flag = 0; 
      answer = ""; 
     } 


    } 

    public void three(View view){ 
     buttonThree = (Button) findViewById(R.id.button_three); 
     checkLength(buttonThree); 
     textViewAnswer.setText(answer); 
    } 

    public void four(View view){ 
     buttonFour = (Button) findViewById(R.id.button_four); 
     checkLength(buttonFour); 
     textViewAnswer.setText(answer); 
    } 

    public void five(View view){ 
     buttonFive = (Button) findViewById(R.id.button_five); 
     checkLength(buttonFive); 
     textViewAnswer.setText(answer); 
    } 

    public void six(View view){ 
     buttonSix = (Button) findViewById(R.id.button_six); 
     checkLength(buttonSix); 
     textViewAnswer.setText(answer); 
    } 

    public void seven(View view){ 
     buttonSeven = (Button) findViewById(R.id.button_seven); 
     checkLength(buttonSeven); 
     textViewAnswer.setText(answer); 
    } 

    public void eight(View view){ 
     buttonEight = (Button) findViewById(R.id.button_eight); 
     checkLength(buttonEight); 
     textViewAnswer.setText(answer); 
    } 

    public void nine(View view){ 
     buttonNine = (Button) findViewById(R.id.button_nine); 
     checkLength(buttonNine); 
     textViewAnswer.setText(answer); 
    } 

    public void zero(View view){ 
     buttonZero = (Button) findViewById(R.id.button_zero); 
     checkLength(buttonZero); 
     textViewAnswer.setText(answer); 
    } 

    public void dot(View view){ 
     buttonDot = (Button) findViewById(R.id.button_dot); 
     checkLength(buttonDot); 
     textViewAnswer.setText(answer); 
    } 

    public void equal(View view){ 
     buttonEqual = (Button) findViewById(R.id.button_equal); 
//  textViewAnswer.setText(buttonEqual.getText().toString()); 
     switch (operation){ 
      case "+" : num2 = num1 + (Float.parseFloat(textViewAnswer.getText().toString())); 
         answer = (String.valueOf(num2)); 
       textViewAnswer.setText(answer); 
     } 
    } 

    public void addition(View view){ 
     buttonAddition = (Button) findViewById(R.id.button_addition); 
     textViewAnswer.setText(buttonAddition.getText().toString()); 
     operation = "+"; 
     flag = 1; 

    } 

    public void substraction(View view){ 
     buttonSubstraction = (Button) findViewById(R.id.button_substraction); 
     textViewAnswer.setText(buttonSubstraction.getText().toString()); 
     operation = "-"; 
    } 

    public void division(View view){ 
     buttonDivision = (Button) findViewById(R.id.button_division); 
     textViewAnswer.setText(buttonDivision.getText().toString()); 
     operation = "/"; 
    } 

    public void multiplication(View view){ 
     buttonMultiplication = (Button) findViewById(R.id.button_multiplication); 
     textViewAnswer.setText(buttonMultiplication.getText().toString()); 
     operation = "*"; 
    } 

    public void checkLength(Button button){ 
     if((answer.length()) < 9) 
      answer += button.getText().toString(); 
     else 
      Toast.makeText(this, "Cannot take more input", Toast.LENGTH_SHORT).show(); 
    } 
}

布局：

<?xml version="1.0" encoding="utf-8"?> 
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.example.darpan.basiccalculator.MainActivity"> 


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

     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:text="Answer" 
      android:id="@+id/textview_answer" 
      android:textSize="50sp"/> 

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

      <Button 
       android:id="@+id/button_one" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="1" 
       android:onClick="one"/> 

      <Button 
       android:id="@+id/button_two" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="2" 
       android:onClick="two"/> 

      <Button 
       android:id="@+id/button_three" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="3" 
       android:onClick="three"/> 

      <Button 
       android:id="@+id/button_addition" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="+" 
       android:onClick="addition"/> 

     </LinearLayout> 

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

      <Button 
       android:id="@+id/button_four" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="4" 
       android:onClick="four"/> 

      <Button 
       android:id="@+id/button_five" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="5" 
       android:onClick="five"/> 

      <Button 
       android:id="@+id/button_six" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="6" 
       android:onClick="six"/> 

      <Button 
       android:id="@+id/button_substraction" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="-" 
       android:onClick="substraction"/> 


     </LinearLayout> 

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

      <Button 

       android:id="@+id/button_seven" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="7" 
       android:onClick="seven"/> 

      <Button 
       android:id="@+id/button_eight" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="8" 
       android:onClick="eight"/> 

      <Button 
       android:id="@+id/button_nine" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="9" 
       android:onClick="nine"/> 
      /> 

      <Button 
       android:id="@+id/button_multiplication" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="*" 
       android:onClick="multiplication"/> 
      /> 

     </LinearLayout> 

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

      <Button 
       android:id="@+id/button_dot" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="." 
       android:onClick="dot"/> 

      <Button 
       android:id="@+id/button_zero" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="0" 
       android:onClick="zero"/> 

      <Button 
       android:id="@+id/button_equal" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="=" 
       android:onClick="equal"/> 

      <Button 
       android:id="@+id/button_division" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_weight="1" 
       android:text="/" 
       android:onClick="division"/> 
     </LinearLayout> 

    </LinearLayout> 
</ScrollView>

来源

2016-06-11 pinku

我不太明白你在说什么。请张贴一些代码，并尝试更好地解释一下。 – Vucko

请发布一些您遇到问题的代码。 –

社区新手..已经习惯了.. – pinku

你只需要重置TextView，不是变量。另外，请在onCreate方法中设置屏幕。我假设你在xml布局文件中声明了按钮方法，所以为了方便起见，只需将它们全部设置为使用相同的方法即可。

int operation; //1 = add, 2 = subt, 3 = div, 4 = mult 
float answer; 
String s; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    textViewAnswer = (TextView) findViewById(R.id.textview_answer); 

    SetupView(); 
} 


public void ButtonPress(View view) { 

    switch (view.getId()){ 

    case R.id.button_one: 
     textViewAnswer.setText(s + "1"); 
      s = textViewAnswer.getText(); 
    break; 

    case R.id.button_two: 
     textViewAnswer.setText(s + "2");    
      s = textViewAnswer.getText(); 
    break; 
    . 
    . 
    . 

    case R.id.button_addition: 
     num1 = Float.parseFloat(textViewAnswer); 
     //insert data persistence here one day (`SharedPreferences`) 
     operation = 1; 
     textViewAnswer.setText(""); 
     break;  
    . 
    . 
    . 

    case R.id.button_equals: 
     num2 = Float.parseFloat(textViewAnswer); 

     switch (operation){ 

     case 1: 
     answer = num1 + num2; 
     textViewAnswer.setText(String.valueOf(answer)) 
     break; 
     . 
     . 
     . 
    } 
} 

Public void SetupView() { 

buttonOne = (Button) findViewById(R.id.button_one); 
buttonTwo = (Button) findViewById(R.id.button_two); 
... etc 
}

来源

2016-06-11 15:50:47 SQLiteNoob

基本计算器Android应用程序

回答

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