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我创建了一个计算器，但每次单击 *,/,+,- 两次时它都会崩溃。我知道它会崩溃，因为您不能进行两次除法/乘法运算，但是如何设置一个规则来检查乘法/除法是否已被单击一次？

这是代码：

package com.example.calculator;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity implements View.OnClickListener {

    Button add1, add2, add3, add4, add5, add6, add7, add8, add9, 
            plus, minus, divide, multiply, equal, add0, clear;
    TextView Display, infobox;
    String x;
    double plusminus, firstDouble, secondDouble, totalDouble;
    boolean plusClick, minusClick, multiplyClick, divideClick;
    int checkMulti = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.calculator);
        initialize();
    }

    void initialize() {
        add0 = (Button) findViewById(R.id.b0);
        // snipped cases for 1 to 8
        add9 = (Button) findViewById(R.id.b9);
        minus = (Button) findViewById(R.id.bSub);
        equal = (Button) findViewById(R.id.bEquals);
        plus = (Button) findViewById(R.id.bAdd);
        clear = (Button) findViewById(R.id.bClear);
        Display = (TextView) findViewById(R.id.tvResults);
        divide = (Button) findViewById(R.id.bDivide);
        multiply = (Button) findViewById(R.id.bMultiply);
        add0.setOnClickListener(this);
        // snipped cases for 1 to 8
        add9.setOnClickListener(this);
        minus.setOnClickListener(this);
        equal.setOnClickListener(this);
        plus.setOnClickListener(this);
        Display.setOnClickListener(this);
        divide.setOnClickListener(this);
        multiply.setOnClickListener(this);
        clear.setOnClickListener(this);
    }    
    @Override
    public void onClick(View v) {       
        switch (v.getId()) {
            case R.id.b0:
            Display.setText(Display.getText() + "0");
            break;
            // ... snipped cases for 1 to 8
            case R.id.b9:
            Display.setText(Display.getText() + "9");
            break;
            case R.id.bAdd:
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            plusClick = true;
            break;  
            case R.id.bSub:
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            minusClick = true;      
            break;
            case R.id.bEquals:
            secondDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            if (plusClick) {
                totalDouble = firstDouble + secondDouble;
                Display.setText((String.valueOf(totalDouble)));
                firstDouble = 0;
                secondDouble = 0;
                plusClick = false;
            }

            if (minusClick) {
                totalDouble = firstDouble - secondDouble;
                Display.setText((String.valueOf(totalDouble)));
                firstDouble = 0;
                secondDouble = 0;
                minusClick = false;
            }           

            if (divideClick) {
                totalDouble = firstDouble / secondDouble;
                Display.setText((String.valueOf(totalDouble)));
                firstDouble = 0;
                secondDouble=0;
                divideClick = false;
            }

            if (multiplyClick) {
                totalDouble = firstDouble * secondDouble;
                Display.setText((String.valueOf(totalDouble)));
                firstDouble = 0;
                secondDouble = 0;
                multiplyClick = false;
            }
            break;      

            case R.id.bMultiply:    
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            multiplyClick = true;
            break;

            case R.id.bDivide:
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            divideClick = true;             
            break;

            case R.id.bClear:
            Display.setText("");
            multiplyClick = false;
            divideClick = false;
            plusClick = false;
            minusClick = false;
            break;
        }
    }
}

如果我没记错的话应该是这样的

        case R.id.bMultiply:
        if (Display.getText() != "") {
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            multiplyClick = true;
        }
        break;

        case R.id.bDivide:
        if (Display.getText() != null) {
            firstDouble = (Double.parseDouble(String.valueOf(Display.getText())));
            Display.setText("");
            divideClick = true;         
        }
        break;

LogCat（07-26 09:00:00 开始）：

04:02.361: E/AndroidRuntime(5387): FATAL EXCEPTION: main
04:02.361: E/AndroidRuntime(5387): java.lang.NumberFormatException: Invalid double: ""
04:02.361: E/AndroidRuntime(5387):  at java.lang.StringToReal.invalidReal(StringToReal.java:63)
04:02.361: E/AndroidRuntime(5387):  at java.lang.StringToReal.parseDouble(StringToReal.java:248)
04:02.361: E/AndroidRuntime(5387):  at java.lang.Double.parseDouble(Double.java:295)
04:02.361: E/AndroidRuntime(5387):  at com.example.calculator.MainActivity.onClick(MainActivity.java:177)
04:02.361: E/AndroidRuntime(5387):  at android.view.View.performClick(View.java:4162)
04:02.361: E/AndroidRuntime(5387):  at android.view.View$PerformClick.run(View.java:17082)
04:02.361: E/AndroidRuntime(5387):  at android.os.Handler.handleCallback(Handler.java:615)
04:02.361: E/AndroidRuntime(5387):  at android.os.Handler.dispatchMessage(Handler.java:92)
04:02.361: E/AndroidRuntime(5387):  at android.os.Looper.loop(Looper.java:137)
04:02.361: E/AndroidRuntime(5387):  at android.app.ActivityThread.main(ActivityThread.java:4856)
04:02.361: E/AndroidRuntime(5387):  at java.lang.reflect.Method.invokeNative(Native Method)
04:02.361: E/AndroidRuntime(5387):  at java.lang.reflect.Method.invoke(Method.java:511)
04:02.361: E/AndroidRuntime(5387):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
04:02.361: E/AndroidRuntime(5387):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
04:02.361: E/AndroidRuntime(5387):  at dalvik.system.NativeStart.main(Native Method)
04:10.429: I/Process(5387): Sending signal. PID: 5387 SIG: 9
19:01.891: D/libEGL(6671): loaded /system/lib/egl/libEGL_mali.so
19:01.901: D/libEGL(6671): loaded /system/lib/egl/libGLESv1_CM_mali.so
19:01.911: D/libEGL(6671): loaded /system/lib/egl/libGLESv2_mali.so
19:01.961: D/OpenGLRenderer(6671): Enabling debug mode 0
19:04.403: D/AndroidRuntime(6671): Shutting down VM
19:04.403: W/dalvikvm(6671): threadid=1: thread exiting with uncaught exception (group=0x418972a0)
19:04.433: E/AndroidRuntime(6671): FATAL EXCEPTION: main
19:04.433: E/AndroidRuntime(6671): java.lang.NumberFormatException: Invalid double: ""
19:04.433: E/AndroidRuntime(6671):  at java.lang.StringToReal.invalidReal(StringToReal.java:63)
19:04.433: E/AndroidRuntime(6671):  at java.lang.StringToReal.parseDouble(StringToReal.java:248)
19:04.433: E/AndroidRuntime(6671):  at java.lang.Double.parseDouble(Double.java:295)
19:04.433: E/AndroidRuntime(6671):  at com.example.calculator.MainActivity.onClick(MainActivity.java:168)
19:04.433: E/AndroidRuntime(6671):  at android.view.View.performClick(View.java:4162)
19:04.433: E/AndroidRuntime(6671):  at android.view.View$PerformClick.run(View.java:17082)
19:04.433: E/AndroidRuntime(6671):  at android.os.Handler.handleCallback(Handler.java:615)
19:04.433: E/AndroidRuntime(6671):  at android.os.Handler.dispatchMessage(Handler.java:92)
19:04.433: E/AndroidRuntime(6671):  at android.os.Looper.loop(Looper.java:137)
19:04.433: E/AndroidRuntime(6671):  at android.app.ActivityThread.main(ActivityThread.java:4856)
19:04.433: E/AndroidRuntime(6671):  at java.lang.reflect.Method.invokeNative(Native Method)
19:04.433: E/AndroidRuntime(6671):  at java.lang.reflect.Method.invoke(Method.java:511)
19:04.433: E/AndroidRuntime(6671):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
19:04.433: E/AndroidRuntime(6671):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
19:04.433: E/AndroidRuntime(6671):  at dalvik.system.NativeStart.main(Native Method)
20:27.315: D/AndroidRuntime(6893): Shutting down VM
20:27.315: W/dalvikvm(6893): threadid=1: thread exiting with uncaught exception (group=0x418972a0)
20:27.325: E/AndroidRuntime(6893): FATAL EXCEPTION: main
20:27.325: E/AndroidRuntime(6893): java.lang.NumberFormatException: Invalid double: ""
20:27.325: E/AndroidRuntime(6893):  at java.lang.StringToReal.invalidReal(StringToReal.java:63)
20:27.325: E/AndroidRuntime(6893):  at java.lang.StringToReal.parseDouble(StringToReal.java:248)
20:27.325: E/AndroidRuntime(6893):  at java.lang.Double.parseDouble(Double.java:295)
20:27.325: E/AndroidRuntime(6893):  at com.example.calculator.MainActivity.onClick(MainActivity.java:168)
20:27.325: E/AndroidRuntime(6893):  at android.view.View.performClick(View.java:4162)
20:27.325: E/AndroidRuntime(6893):  at android.view.View$PerformClick.run(View.java:17082)
20:27.325: E/AndroidRuntime(6893):  at android.os.Handler.handleCallback(Handler.java:615)
20:27.325: E/AndroidRuntime(6893):  at android.os.Handler.dispatchMessage(Handler.java:92)
20:27.325: E/AndroidRuntime(6893):  at android.os.Looper.loop(Looper.java:137)
20:27.325: E/AndroidRuntime(6893):  at android.app.ActivityThread.main(ActivityThread.java:4856)
20:27.325: E/AndroidRuntime(6893):  at java.lang.reflect.Method.invokeNative(Native Method)
20:27.325: E/AndroidRuntime(6893):  at java.lang.reflect.Method.invoke(Method.java:511)
20:27.325: E/AndroidRuntime(6893):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
20:27.325: E/AndroidRuntime(6893):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
20:27.325: E/AndroidRuntime(6893):  at dalvik.system.NativeStart.main(Native Method)
23:16.225: D/AndroidRuntime(7204): Shutting down VM
23:16.225: W/dalvikvm(7204): threadid=1: thread exiting with uncaught exception (group=0x418972a0)
23:16.245: E/AndroidRuntime(7204): FATAL EXCEPTION: main
23:16.245: E/AndroidRuntime(7204): java.lang.NumberFormatException: Invalid double: ""
23:16.245: E/AndroidRuntime(7204):  at java.lang.StringToReal.invalidReal(StringToReal.java:63)
23:16.245: E/AndroidRuntime(7204):  at java.lang.StringToReal.parseDouble(StringToReal.java:248)
23:16.245: E/AndroidRuntime(7204):  at java.lang.Double.parseDouble(Double.java:295)
23:16.245: E/AndroidRuntime(7204):  at com.example.calculator.MainActivity.onClick(MainActivity.java:176)
23:16.245: E/AndroidRuntime(7204):  at android.view.View.performClick(View.java:4162)
23:16.245: E/AndroidRuntime(7204):  at android.view.View$PerformClick.run(View.java:17082)
23:16.245: E/AndroidRuntime(7204):  at android.os.Handler.handleCallback(Handler.java:615)
23:16.245: E/AndroidRuntime(7204):  at android.os.Handler.dispatchMessage(Handler.java:92)
23:16.245: E/AndroidRuntime(7204):  at android.os.Looper.loop(Looper.java:137)
23:16.245: E/AndroidRuntime(7204):  at android.app.ActivityThread.main(ActivityThread.java:4856)
23:16.245: E/AndroidRuntime(7204):  at java.lang.reflect.Method.invokeNative(Native Method)
23:16.245: E/AndroidRuntime(7204):  at java.lang.reflect.Method.invoke(Method.java:511)
23:16.245: E/AndroidRuntime(7204):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
23:16.245: E/AndroidRuntime(7204):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
23:16.245: E/AndroidRuntime(7204):  at dalvik.system.NativeStart.main(Native Method)
4

1 回答 1

1

1）您还应该发布错误日志以了解程序崩溃的确切原因。

2) 在设置 Display.setText(""); 之前它可能会崩溃；完成计算后显示为空白。如果您下次再次按下 除法，它将尝试将毯子解析为 Double 但它是空的“”，因此它在解析空白空间时崩溃。可能还有其他错误，您必须查看错误日志。

3）在您提出的 if 条件中，您必须检查 Display.getText().toString() 是否为有效数字且不为空且大于零。但是再次查看您的错误日志以了解您的应用程序崩溃的原因。

于 2013-07-26T01:19:20.290 回答