java - 当我设置类实例时，我的 Android 应用程序崩溃了

Question

我对 Android 编程很陌生。我正在开发一个应用程序，它可以很好地打开并且几乎可以按照我想要的方式工作。但我有一个问题，我不知道解决它的方法。这就是问题所在:我正在用一个值填充 EditText，并且在我的 java 代码中该值将初始化我创建的对象。但这永远不会发生，因为任何初始化对象的尝试都会使我的应用程序崩溃。我在其中输入值以初始化对象的editText 是名为spotText 的editText。有人可以帮忙吗？这是 XML 代码:

<LinearLayout 
    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"
    android:background="#000000"
    android:orientation="vertical"
    tools:context=".MainActivity" >

<ScrollView    
android:id="@+id/scroll"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:scrollbars="none">

<HorizontalScrollView 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">

<TableLayout
    android:id="@+id/TheTable"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:stretchColumns="0,1,2,3,4,5,6,7,8,9,10,11,12" >        

 <TableRow
     android:id="@+id/tbRow1"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content" >

  <TextView
    android:id="@+id/spot"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingRight="10dp"
    android:text="@string/spot"
    android:textSize="10sp"
    android:gravity="center"
    android:textColor="@color/white" />

  <TextView
        android:id="@+id/div"               
        android:text="@string/div"
        android:gravity="center"
        android:textColor="@color/white"
        android:textSize="10sp" />      

    <TextView
        android:id="@+id/rate"
        android:text="@string/Rate"
        android:gravity="center"
        android:textColor="@color/white"
        android:textSize="10sp" />

    <CheckBox 
        android:id="@+id/smile"
        android:text="@string/UseSmile"             
        android:textColor="@color/white"
        android:textSize="10sp"/>

    <TextView
        android:id="@+id/ATM"
        android:text="@string/ATM"
        android:gravity="center"
        android:textColor="@color/white"
        android:textSize="10sp" />
</TableRow>

<TableRow
    android:id="@+id/tbRow2"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" >

    <EditText
        android:id="@+id/spotText"
        android:hint="@string/Spot"
        android:gravity="center"      
        android:inputType="numberSigned"
        android:textColor="@color/white"
        android:textSize="10sp" />

    <EditText
        android:id="@+id/divRate"
        android:hint="@string/divRate"
        android:gravity="center"    
        android:inputType="numberDecimal"
        android:textColor="@color/white"
        android:textSize="10sp" />

    <EditText
        android:id="@+id/IR"
        android:hint="@string/IRate"
        android:gravity="center"    
        android:inputType="numberDecimal"
        android:textColor="@color/white"
        android:textSize="10sp" />
    <EditText
        android:id="@+id/ATMVOL"
        android:hint="@string/ATM"
        android:layout_column="4"
        android:gravity="center"    
        android:inputType="numberDecimal"
        android:textColor="@color/white"
        android:textSize="10sp" />

</TableRow>        

            <TableRow
                android:id="@+id/tbRow3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" >

                <TextView
                    android:id="@+id/product"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/product"
                    android:gravity="center"
                    android:textSize="10sp"
                    android:textColor="@color/white" />


                <TextView
                    android:id="@+id/strike"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/strike"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/maturity"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/maturity"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/vol"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:text="@string/volatility"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/Qty"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:text="@string/Quantity"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/price"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="15dp"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:text="@string/price"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/delta"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/delta"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/gamma"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/gamma"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/theta"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/theta"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/vega"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/vega"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/vanna"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/vanna"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />

                <TextView
                    android:id="@+id/vomma"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingRight="10dp"
                    android:text="@string/vomma"
                    android:textSize="10sp"
                    android:gravity="center"
                    android:textColor="@color/white" />
            </TableRow>
            <TableRow
                android:id="@+id/tbRow4" >
                <Spinner 
                    android:id="@+id/spin1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:dropDownSelector="@string/Product"
                    android:prompt="@string/Product"
                    android:entries="@array/Array"
                    android:background="@color/SpinColor"
                    android:textSize="10sp"/>
                <EditText
                    android:id="@+id/K1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:hint="K"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <EditText
                    android:id="@+id/T1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:hint="T"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <EditText
                    android:id="@+id/Vol1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:hint="Vol"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <EditText
                    android:id="@+id/Qty1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:hint="Qty"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/Px1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>           
                <TextView
                    android:id="@+id/delta1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/gamma1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/theta1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/vega1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/vanna1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
                <TextView
                    android:id="@+id/vomma1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:textSize="10sp"/>
            </TableRow>

            <TableRow
                android:id="@+id/tbRow9">                
                 <Button 
                    android:id="@+id/delBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textSize="10sp"
                    android:text="@string/delete"/>
                <Button 
                    android:id="@+id/addBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textSize="10sp"
                    android:text="@string/Add"/>

            </TableRow>
        </TableLayout>

   </HorizontalScrollView>
</ScrollView>            

这是MainActivity类代码

    package com.example.lilpricer;

    import android.app.Activity;
    import android.os.Bundle;
    import android.text.Editable;
    import android.text.TextWatcher;
    import android.view.Menu;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.CheckBox;
    import android.widget.CompoundButton;
    import android.widget.CompoundButton.OnCheckedChangeListener;
    import android.widget.EditText;
    import android.widget.Spinner;
    import android.widget.TableRow;
    import android.widget.TextView;

    public class MainActivity extends Activity {

int nbRow = 1;

TableRow tb1 = null; TableRow tb2 = null; TableRow tb3 = null; TableRow tb4 = null;
TableRow tb5 = null; TableRow tb6 = null; TableRow tb7 = null; TableRow tb8 = null;
TableRow tb9 = null; 
TextView tvVol = null; TextView tvSpot;
EditText etSpot = null; EditText etDiv = null; EditText etIR = null; EditText etVol = null;
EditText etK1= null; EditText etK2= null; EditText etK3 = null; EditText etK4= null;
EditText etMat1= null; EditText etMat2= null; EditText etMat3 = null; EditText etMat4= null;
EditText etVol1= null; EditText etVol2= null; EditText etVol3 = null; EditText etVol4= null;
EditText etQty1= null; EditText etQty2= null; EditText etQty3 = null; EditText etQty4= null;
Spinner spin1 = null; Spinner spin2 = null; Spinner spin3 = null; Spinner spin4 = null;
Button Del = null; Button Add = null; Button Price = null;
CheckBox cbSmile = null;
Stock S=null; 
Future Fut1 = null; Future Fut2 = null; Future Fut3 = null; Future Fut4 = null;
Option Opt1 = null; Option Opt2 = null; Option Opt3 = null; Option Opt4 = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    setWidgetRef();


    tb5.setVisibility(View.INVISIBLE); tb6.setVisibility(View.INVISIBLE); tb7.setVisibility(View.INVISIBLE); 
    tvVol.setVisibility(View.INVISIBLE); etVol.setVisibility(View.INVISIBLE);       


    etSpot.addTextChangedListener(new TextWatcher() {
        double TheSpot= 0;          
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            // TODO Auto-generated method stub
            TheSpot=Double.parseDouble(etSpot.getText().toString());                
            S.SetStock(TheSpot);
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable s) {
            // TODO Auto-generated method stub

        }
    });
}


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



private void setWidgetRef()
    {
        tb1 = (TableRow) findViewById(R.id.tbRow1); tb2 = (TableRow) findViewById(R.id.tbRow2);
        tb3 = (TableRow) findViewById(R.id.tbRow3); tb4 = (TableRow) findViewById(R.id.tbRow4);
        tb5 = (TableRow) findViewById(R.id.tbRow5); tb6 = (TableRow) findViewById(R.id.tbRow6);
        tb7 = (TableRow) findViewById(R.id.tbRow7); tb8 = (TableRow) findViewById(R.id.tbRow8);
        tb9 = (TableRow) findViewById(R.id.tbRow9); 

        etSpot = (EditText) findViewById(R.id.spotText); etDiv=(EditText) findViewById(R.id.divRate); 
        etIR= (EditText) findViewById(R.id.IR); etVol = (EditText) findViewById(R.id.ATMVOL);
        etK1= (EditText) findViewById(R.id.K1); etK2= (EditText) findViewById(R.id.K2);
        etK3= (EditText) findViewById(R.id.K3); etK4= (EditText) findViewById(R.id.K4);
        etMat1 = (EditText) findViewById(R.id.T1);etMat2 = (EditText) findViewById(R.id.T2); 
        etMat3 = (EditText) findViewById(R.id.T3);etMat4 = (EditText) findViewById(R.id.T4);
        etVol1 =(EditText) findViewById(R.id.Vol1);etVol2 =(EditText) findViewById(R.id.Vol2);
        etVol3 =(EditText) findViewById(R.id.Vol3);etVol4 =(EditText) findViewById(R.id.Vol4);
        etQty1=(EditText)  findViewById(R.id.Qty1); etQty2=(EditText)  findViewById(R.id.Qty2); 
        etQty3=(EditText)  findViewById(R.id.Qty3); etQty4=(EditText)  findViewById(R.id.Qty4);

        tvVol = (TextView) findViewById(R.id.ATM); tvSpot = (TextView) findViewById(R.id.spot);

        Del = (Button) findViewById(R.id.delBtn); Add = (Button) findViewById(R.id.addBtn);
        Price = (Button) findViewById(R.id.priceBtn);

        cbSmile = (CheckBox) findViewById(R.id.smile);

        spin1 = (Spinner) findViewById(R.id.spin1);spin2 = (Spinner) findViewById(R.id.spin2);
        spin3 = (Spinner) findViewById(R.id.spin3);spin4 = (Spinner) findViewById(R.id.spin4);
    }
    }

这是我尝试初始化实例的类

    package com.example.lilpricer;

public class Stock {
private double S;   

Stock(double Price){
    S=Math.abs(Price);
}

Stock(){
    this.S=0;
}
public void SetStock(double price) {
    // TODO Auto-generated method stub
    S=Math.abs(price);
}
}

这是应用程序崩溃时的 logcat。正如您所看到的，它似乎是 EditText 中的 NullPointerException，其中我输入了初始化对象 Stock 的值，但我不明白为什么会出现这样的错误，因为我在 java 中定义了一个 EditText 并将其与 EditText 链接起来我的 XML 页面，与我的对象(此处名为 S)相同，它已被定义为全局变量，因此它存在。我显然在这里遗漏了一些东西，但我只是看不出它是什么。非常感谢您的帮助。

01-06 02:06:24.770: E/AndroidRuntime(5721): FATAL EXCEPTION: main
01-06 02:06:24.770: E/AndroidRuntime(5721): java.lang.NullPointerException
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.example.lilpricer.MainActivity$1.onTextChanged(MainActivity.java:144)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.TextView.sendOnTextChanged(TextView.java:7092)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.TextView.handleTextChanged(TextView.java:7151)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.TextView$ChangeWatcher.onTextChanged(TextView.java:8794)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.text.SpannableStringBuilder.sendTextChanged(SpannableStringBuilder.java:962)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:496)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:435)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:30)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.text.method.NumberKeyListener.onKeyDown(NumberKeyListener.java:121)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.TextView.doKeyDown(TextView.java:5246)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.TextView.onKeyDown(TextView.java:5065)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.KeyEvent.dispatch(KeyEvent.java:2609)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.View.dispatchKeyEvent(View.java:7198)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.HorizontalScrollView.dispatchKeyEvent(HorizontalScrollView.java:332)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.widget.ScrollView.dispatchKeyEvent(ScrollView.java:353)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1920)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1395)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.app.Activity.dispatchKeyEvent(Activity.java:2370)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1847)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3701)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3651)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2818)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.os.Looper.loop(Looper.java:137)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at android.app.ActivityThread.main(ActivityThread.java:5039)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at java.lang.reflect.Method.invokeNative(Native Method)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at java.lang.reflect.Method.invoke(Method.java:511)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-06 02:06:24.770: E/AndroidRuntime(5721):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

您从未实例化该类。在使用S之前添加S=new Stock()或S=new Stock(price)；