致命异议：主要。 （运行时异常）。 Android的

Question

我是android的新手。我刚刚尝试创建一个执行基本数学运算（加法，减法，乘法和除法）的简单应用程序。当我尝试运行代码时出现FATAL EXCEPTION: main错误。我已经完成了其他遇到同样问题的线程。我仍然无法弄清楚为什么我有这个错误。

mainactivity.java文件是     package com.example.mathematicalopr;

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

public class MainActivity extends Activity {

    Button add,sub,mul,div;
    TextView display2;
    EditText display,display1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        //int c=0;
        add = (Button) findViewById(R.id.bAdd);
        sub = (Button) findViewById(R.id.bSub);
        mul = (Button) findViewById(R.id.times);
        div = (Button) findViewById(R.id.divide);


        display = (EditText) findViewById(R.id.tvDisplay);
        String myFirstNum = display.getText().toString();
        final int a = Integer.parseInt(myFirstNum);
        display1 = (EditText) findViewById(R.id.tvDisplay1);
        String mySecondNum = display1.getText().toString();
        final int b = Integer.parseInt(mySecondNum);
        display2 = (TextView) findViewById(R.id.tvDisplay2);
        add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                int c = a+b;
                display2.setText("Answer is"+c);
            }
        });
        sub.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                int c = a-b; 
                display2.setText("Answer is"+c);
            }
        });
            mul.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                int c = a*b; 
                display2.setText("Answer is"+c);
            }
        });
    div.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        int c = a/b; 
        display2.setText("Answer is"+c);
    }
        });
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    }

我的activity_main.xml文件是

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:orientation="vertical" >

    <EditText
    android:id="@+id/tvDisplay"
    android:layout_width="342dp"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:text="@string/ref" />
    <EditText
    android:id="@+id/tvDisplay1"
    android:layout_width="342dp"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:text="@string/ref1" />


    <Button
    android:id="@+id/bAdd"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="center"
    android:text="@string/add" />

    <Button
    android:id="@+id/bSub"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="center"
    android:text="@string/sub" />
    <Button
    android:id="@+id/times"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="center"
    android:text="@string/times" />
    <Button
    android:id="@+id/divide"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="center"
    android:text="@string/divide" />
   <TextView
    android:id="@+id/tvDisplay2"
    android:layout_width="342dp"
    android:layout_height="wrap_content"
    android:text="@string/ref2" />
    </LinearLayout>

我的strings.xml文件

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

    <string name="app_name">Mathematicalopr</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>
    <string name="ref">Enter first number</string>
    <string name="add">Add</string>
    <string name="sub">Subtract </string>
    <string name="times">Multiply</string>
    <string name="divide">divide</string>
    <string name="ref1">Enter second number</string>
    <string name="ref2">Answer is</string>

</resources>

logcat的：

02-08 10:50:43.962: W/Trace(2302): Unexpected value from nativeGetEnabledTags: 0
02-08 10:50:43.972: W/Trace(2302): Unexpected value from nativeGetEnabledTags: 0
02-08 10:50:43.972: W/Trace(2302): Unexpected value from nativeGetEnabledTags: 0
02-08 10:50:44.022: W/Trace(2302): Unexpected value from nativeGetEnabledTags: 0
02-08 10:50:44.022: W/Trace(2302): Unexpected value from nativeGetEnabledTags: 0
02-08 10:50:44.422: D/AndroidRuntime(2302): Shutting down VM
02-08 10:50:44.432: W/dalvikvm(2302): threadid=1: thread exiting with uncaught exception (group=0xb2ca6908)
02-08 10:50:44.462: E/AndroidRuntime(2302): FATAL EXCEPTION: main
02-08 10:50:44.462: E/AndroidRuntime(2302): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mathematicalopr/com.example.mathematicalopr.MainActivity}: java.lang.NumberFormatException: Invalid int: "Enter first number"
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.os.Looper.loop(Looper.java:137)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread.main(ActivityThread.java:5039)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.reflect.Method.invokeNative(Native Method)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.reflect.Method.invoke(Method.java:511)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at dalvik.system.NativeStart.main(Native Method)
02-08 10:50:44.462: E/AndroidRuntime(2302): Caused by: java.lang.NumberFormatException: Invalid int: "Enter first number"
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.Integer.invalidInt(Integer.java:138)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.Integer.parse(Integer.java:375)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.Integer.parseInt(Integer.java:366)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at java.lang.Integer.parseInt(Integer.java:332)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at com.example.mathematicalopr.MainActivity.onCreate(MainActivity.java:30)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.Activity.performCreate(Activity.java:5104)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-08 10:50:44.462: E/AndroidRuntime(2302):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-08 10:50:44.462: E/AndroidRuntime(2302):     ... 11 more

我能知道为什么会出现这样的错误吗？当我尝试在虚拟设备上运行此代码时，应用程序意外关闭。谢谢:)）

谢谢大家。很抱歉显然我没有足够的声誉来感谢你们每个人。

Answer 1

你的Logcat说明了一切，

阅读本文

无效的int：“输入第一个数字”

您正在将字符串值转换为int，结果为java.lang.NumberFormatException。

Answer 2

你必须改变

<EditText
 android:id="@+id/tvDisplay"
 android:layout_width="342dp"
 android:layout_height="wrap_content"
 android:inputType="number"
 android:hint="@string/ref" />

<EditText
 android:id="@+id/tvDisplay1"
 android:layout_width="342dp"
 android:layout_height="wrap_content"
 android:inputType="number"
 android:hint="@string/ref1" />

你必须从

改变

android:text="@string/ref1"

到

android:hint="@string/ref1"

因为在oncreate（）方法中，您正在检索EditText的值。在xml中你已经为它设置了字符串，之后你在Integer中解析了它。所以你得到了无效的int错误。所以只需为每个EditText更改它。

您正在将字符串值转换为int，这会导致java.lang.NumberFormatException。

Answer 3

    String myFirstNum = display.getText().toString();
    final int a = Integer.parseInt(myFirstNum);


    String mySecondNum = display1.getText().toString();
    final int b = Integer.parseInt(mySecondNum);

在添加按钮单击事件监听器中插入此代码，然后您将获得正确的数据

Answer 4

修改了你的代码：

package com.example.sampleactivity;

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

public class MainActivity extends Activity {

    Button add,sub,mul,div;
    TextView display2;
    EditText display,display1;
    int a,b,c;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        //int c=0;
        add = (Button) findViewById(R.id.bAdd);
        sub = (Button) findViewById(R.id.bSub);
        mul = (Button) findViewById(R.id.times);
        div = (Button) findViewById(R.id.divide);


        display = (EditText) findViewById(R.id.tvDisplay);

        display1 = (EditText) findViewById(R.id.tvDisplay1);

        display2 = (TextView) findViewById(R.id.tvDisplay2);
        add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                getValues();
                c = a+b;
                display2.setText("Answer is"+c);
            }
        });
        sub.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                            getValues();
                c = a-b; 
                display2.setText("Answer is"+c);
            }
        });
        mul.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                            getValues();
                c = a*b; 
                display2.setText("Answer is"+c);
            }
        });
        div.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                            getValues();
                c = a/b; 
                display2.setText("Answer is"+c);
            }
        });
    }


    protected void getValues() {
        String myFirstNum = display.getText().toString();
        a= Integer.parseInt(myFirstNum);
        String mySecondNum = display1.getText().toString();
        b = Integer.parseInt(mySecondNum);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

的xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <EditText
        android:id="@+id/tvDisplay"
        android:layout_width="342dp"
        android:layout_height="wrap_content"
        android:hint="@string/ref"
        android:inputType="number" />

    <EditText
        android:id="@+id/tvDisplay1"
        android:layout_width="342dp"
        android:layout_height="wrap_content"
        android:hint="@string/ref1"
        android:inputType="number" />

    <Button
        android:id="@+id/bAdd"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:text="@string/add" />

    <Button
        android:id="@+id/bSub"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:text="@string/sub" />

    <Button
        android:id="@+id/times"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:text="@string/times" />

    <Button
        android:id="@+id/divide"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:text="@string/divide" />

    <TextView
        android:id="@+id/tvDisplay2"
        android:layout_width="342dp"
        android:layout_height="wrap_content"
        android:text="@string/ref2" />

</LinearLayout>