Java 使用编辑文本进行计算

我正在制作一个简单的应用程序，在计算钱柜时使用。 我对输入数字的编辑文本有问题

应用程序中发生的事情是，用户输入每个纸币和硬币的读数，然后在单击按钮时进行计算，并给出新活动的结果

应用程序立即崩溃，我相信这可能是我试图从编辑文本中获取值的方式

我已经提供了我的代码和错误日志，我是android开发的新手，所以如果这是一件愚蠢的事情，我深表歉意

提前谢谢

TillCounter.java活动

package com.example.tillcounter;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class TillCounter extends Activity implements OnClickListener{

Button calcButton;
EditText readingIn, floatIn, noteIn, fiftiesIn, twentiesIn, tensIn, fivesIn, twosIn,     onesIn, fiftyCentsIn, twentyCentsIn, tenCentsIn;
TextView resultOut;


//int reading = new Integer(readingIn.intValue());
double reading = Double.parseDouble(readingIn.getText().toString());
double tillFloat = Double.parseDouble(floatIn.getText().toString());
double largeNotes = Double.parseDouble(noteIn.getText().toString());
double fifties = Double.parseDouble(fiftiesIn.getText().toString());
double twenties = Double.parseDouble(twentiesIn.getText().toString());
double tens = Double.parseDouble(tensIn.getText().toString());
double fives = Double.parseDouble(fivesIn.getText().toString());
double twos = Double.parseDouble(twosIn.getText().toString());
double ones = Double.parseDouble(onesIn.getText().toString());
double fiftyC = Double.parseDouble(fiftyCentsIn.getText().toString());
double twentyC = Double.parseDouble(twentyCentsIn.getText().toString());
double tenC = Double.parseDouble(tenCentsIn.getText().toString());

double result = 0;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_till_counter);

    resultOut = (TextView) findViewById(R.id.textView1);

    Button calcButton = (Button) findViewById(R.id.calcButton);
    calcButton.setOnClickListener(this);

}

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

@Override
public void onClick(View v) {
    Log.i("clicks","You Clicked calculate");

    result = (reading - tillFloat - largeNotes - fifties - twenties - tens - fives - twos      - ones - fiftyC - twentyC - tenC);

    if(result > 0){
        resultOut.setText("The till is up by: " + result);
    }else if(result < 0){
        resultOut.setText("The till is down by: " + result);
    }else{
        resultOut.setText("The till is even at: " + reading);
    }

    Intent i=new Intent(TillCounter.this, ResultActivity.class);
    startActivity(i);
    }



}

错误日志

    09-03 11:56:58.033: E/Trace(19124): error opening trace file: No such file or directory (2)
09-03 11:56:58.063: W/dalvikvm(19124): threadid=1: thread exiting with uncaught exception (group=0x40d59378)
09-03 11:56:58.073: E/AndroidRuntime(19124): FATAL EXCEPTION: main
09-03 11:56:58.073: E/AndroidRuntime(19124): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.tillcounter/com.example.tillcounter.TillCounter}: java.lang.NullPointerException
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1995)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2096)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread.access$600(ActivityThread.java:138)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1207)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.os.Looper.loop(Looper.java:213)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread.main(ActivityThread.java:4787)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at java.lang.reflect.Method.invokeNative(Native Method)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at java.lang.reflect.Method.invoke(Method.java:511)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at dalvik.system.NativeStart.main(Native Method)
09-03 11:56:58.073: E/AndroidRuntime(19124): Caused by: java.lang.NullPointerException
09-03 11:56:58.073: E/AndroidRuntime(19124):    at com.example.tillcounter.TillCounter.<init>(TillCounter.java:22)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at java.lang.Class.newInstanceImpl(Native Method)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at java.lang.Class.newInstance(Class.java:1319)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-03 11:56:58.073: E/AndroidRuntime(19124):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1986)
09-03 11:56:58.073: E/AndroidRuntime(19124):    ... 11 more

---

很简单。您尝试在屏幕上显示活动之前获取值

把这句话写下来

double reading = Double.parseDouble(readingIn.getText().toString());
double tillFloat = Double.parseDouble(floatIn.getText().toString());
double largeNotes = Double.parseDouble(noteIn.getText().toString());
double fifties = Double.parseDouble(fiftiesIn.getText().toString());
double twenties = Double.parseDouble(twentiesIn.getText().toString());
double tens = Double.parseDouble(tensIn.getText().toString());
double fives = Double.parseDouble(fivesIn.getText().toString());
double twos = Double.parseDouble(twosIn.getText().toString());
double ones = Double.parseDouble(onesIn.getText().toString());
double fiftyC = Double.parseDouble(fiftyCentsIn.getText().toString());
double twentyC = Double.parseDouble(twentyCentsIn.getText().toString());
double tenC = Double.parseDouble(tenCentsIn.getText().toString());

double result = 0;

---

在

onCreate

方法中，而不是在之前。

您应该在设置布局后首先引用所有

EditText

，即

setContentView

。 然后写下所有的代码

代码应该是

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_till_counter);

    readingIn = (EditText) findViewById(R.id.readingIn);
    //and so on for floatIn, noteIn, fiftiesIn etc..

    //int reading = new Integer(readingIn.intValue());
    reading = Double.parseDouble(readingIn.getText().toString());
    tillFloat = Double.parseDouble(floatIn.getText().toString());
    largeNotes = Double.parseDouble(noteIn.getText().toString());
    fifties = Double.parseDouble(fiftiesIn.getText().toString());
    twenties = Double.parseDouble(twentiesIn.getText().toString());
    tens = Double.parseDouble(tensIn.getText().toString());
    fives = Double.parseDouble(fivesIn.getText().toString());
    twos = Double.parseDouble(twosIn.getText().toString());
    ones = Double.parseDouble(onesIn.getText().toString());
    fiftyC = Double.parseDouble(fiftyCentsIn.getText().toString());
    twentyC = Double.parseDouble(twentyCentsIn.getText().toString());
    tenC = Double.parseDouble(tenCentsIn.getText().toString());

    //other code
}

---

就像你已经初始化了你的

TextView结果一样

你也应该初始化你的EditText，你用它来从用户那里获取输入，比如

readingIn=（EditText）findViewById（R.id.your_edit_text）

。另外，当你赋值时，readingIn值是空的。您可以指定方法中的所有值，并可以在计算时调用该方法

package com.example.tillcounter;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

 public class TillCounter extends Activity implements OnClickListener{

 Button calcButton;
 EditText readingIn, floatIn, noteIn, fiftiesIn, twentiesIn, tensIn, fivesIn, twosIn,....;       
 TextView resultOut;
 double reading, tillFloat, largeNotes, fifties ,…..;

 @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_till_counter);

resultOut = (TextView) findViewById(R.id.textView1);
readingIn = (TextView) findViewById(R.id. readingIn);
floatIn = (TextView) findViewById(R.id. floatIn);
noteIn = (TextView) findViewById(R.id. noteIn);
twentiesIn = (TextView) findViewById(R.id. twentiesIn);
///So on


Button calcButton = (Button) findViewById(R.id.calcButton);
calcButton.setOnClickListener(this);

}

 @Override
 public void onClick(View v) {
     Log.i("clicks","You Clicked calculate");
     calculate();
     result = (reading - tillFloat - largeNotes - fifties - twenties - tens -            
         fives - twos      - ones - fiftyC - twentyC - tenC);
     if(result > 0){
     resultOut.setText("The till is up by: " + result);
       }else if(result < 0){
     resultOut.setText("The till is down by: " + result);
     }else{
      resultOut.setText("The till is even at: " + reading);
 }

     Intent i=new Intent(TillCounter.this, ResultActivity.class);
     startActivity(i);
   }
    public void calculate(){
      reading = Double.parseDouble(readingIn.getText().toString());
     tillFloat = Double.parseDouble(floatIn.getText().toString());
      largeNotes = Double.parseDouble(noteIn.getText().toString());
      fifties = Double.parseDouble(fiftiesIn.getText().toString());
      twenties = Double.parseDouble(twentiesIn.getText().toString());
     ////so on
 }

}

package com.example.tillcounter；
导入android.os.Bundle；
导入android.app.Activity；
导入android.content.Intent；
导入android.util.Log；
导入android.view.Menu；
导入android.view.view；
导入android.view.view.OnClickListener；
导入android.widget.Button；
导入android.widget.EditText；
导入android.widget.TextView；
公共类TillCounter扩展活动实现OnClickListener{
按钮calcButton；
编辑文本读入，浮动，注释，五十辛，二十辛，时态，五辛，二辛，。。。。；
文本视图结果；
双读，tillFloat，largeNotes，五十年代，…。。；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity\u-till\u计数器）；
resultOut=（TextView）findViewById（R.id.textView1）；
readingIn=（TextView）findViewById（R.id.readingIn）；
floatIn=（TextView）findViewById（R.id.floatIn）；
noteIn=（TextView）findViewById（R.id.noteIn）；
twentiesIn=（TextView）findViewById（R.id.twentiesIn）；
///诸如此类
按钮calcButton=（按钮）findViewById（R.id.calcButton）；
setOnClickListener（this）；
}
@凌驾
公共void onClick（视图v）{
Log.i（“点击”，“你点击了计算”）；
计算（）；
结果=（读数-tillFloat-largeNotes-五十-二十-十-
五,二,一,五,二十,十;；
如果（结果>0）{
resultOut.setText（“钱柜由：“+result”打开）；
}否则如果（结果<0）{
resultOut.setText（“收银机下降了：“+result”）；
}否则{
resultOut.setText（“收银机在：+读数处为偶数”）；
}
意图i=新意图（TillCounter.this、ResultActivity.class）；
星触觉（i）；
}
公共空间计算（）{
reading=Double.parseDouble（readingIn.getText（）.toString（））；
tillFloat=Double.parseDouble（floatIn.getText（）.toString（））；
largeNotes=Double.parseDouble（noteIn.getText（）.toString（））；
五十个=Double.parseDouble（五十个sin.getText（）.toString（））；
twenties=Double.parseDouble（twentiesIn.getText（）.toString（））；
////诸如此类
}
}

您没有初始化为

readingIn = (EditText) findViewById(R.id.name_edittext);

然后，您需要在创建活动中写入

OnCreate

Activity

double reading = Double.parseDouble(readingIn.getText().toString());

---

你是如何获得信息的？您的EditText代码在哪里？通过编辑文本，我试图将其存储在一个变量中，并使用该变量进行计算。下面有很多相同的解决方案，请选择任何解决方案。如果有帮助，您应该接受任何答案：）

package com.example.tillcounter;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

 public class TillCounter extends Activity implements OnClickListener{

 Button calcButton;
 EditText readingIn, floatIn, noteIn, fiftiesIn, twentiesIn, tensIn, fivesIn, twosIn,....;       
 TextView resultOut;
 double reading, tillFloat, largeNotes, fifties ,…..;

 @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_till_counter);

resultOut = (TextView) findViewById(R.id.textView1);
readingIn = (TextView) findViewById(R.id. readingIn);
floatIn = (TextView) findViewById(R.id. floatIn);
noteIn = (TextView) findViewById(R.id. noteIn);
twentiesIn = (TextView) findViewById(R.id. twentiesIn);
///So on


Button calcButton = (Button) findViewById(R.id.calcButton);
calcButton.setOnClickListener(this);

}

 @Override
 public void onClick(View v) {
     Log.i("clicks","You Clicked calculate");
     calculate();
     result = (reading - tillFloat - largeNotes - fifties - twenties - tens -            
         fives - twos      - ones - fiftyC - twentyC - tenC);
     if(result > 0){
     resultOut.setText("The till is up by: " + result);
       }else if(result < 0){
     resultOut.setText("The till is down by: " + result);
     }else{
      resultOut.setText("The till is even at: " + reading);
 }

     Intent i=new Intent(TillCounter.this, ResultActivity.class);
     startActivity(i);
   }
    public void calculate(){
      reading = Double.parseDouble(readingIn.getText().toString());
     tillFloat = Double.parseDouble(floatIn.getText().toString());
      largeNotes = Double.parseDouble(noteIn.getText().toString());
      fifties = Double.parseDouble(fiftiesIn.getText().toString());
      twenties = Double.parseDouble(twentiesIn.getText().toString());
     ////so on
 }

}

readingIn = (EditText) findViewById(R.id.name_edittext);

double reading = Double.parseDouble(readingIn.getText().toString());