使用EditText进行计算

时间：2013-09-03 11:13:30

标签： java android android-activity android-edittext error-log

我正在制作一个简单的应用程序，用于计算一个直到。 编辑文本输入数字时遇到问题。

在应用程序中发生的事情是用户输入收据的读数，然后输入每个单独的纸币和硬币的金额，并在点击按钮时进行计算，并为您提供新活动的结果。

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。

我提供了我的代码和错误日志，我是Android开发的新手，所以如果它的东西很傻就道歉。

提前致谢。

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);
    }



}

ResultActivity.java 

package com.example.tillcounter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

 public class ResultActivity extends Activity{

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

}

}

错误记录

    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

-------- UPDATE ----------- 正如下面的评论所示，顺便说一句，谢谢你，这是我的主要活动，不幸的是它仍然崩溃。

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;
double reading, tillFloat, largeNotes, fifties, twenties, tens, fives, twos, ones, fiftyC, twentyC, tenC;

//int reading = new Integer(readingIn.intValue());

double result = 0;

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

    resultOut = (TextView) findViewById(R.id.results);
     readingIn = (EditText) findViewById(R.id.readingIn);
     floatIn = (EditText) findViewById(R.id.floatIn);
     noteIn = (EditText) findViewById(R.id.notesIn);
     fiftiesIn = (EditText) findViewById(R.id.fiftiesIn);
     twentiesIn = (EditText) findViewById(R.id.twentiesIn);
     tensIn = (EditText) findViewById(R.id.tensIn);
     fivesIn = (EditText) findViewById(R.id.fivesIn);
     twosIn = (EditText) findViewById(R.id.twosIn);
     onesIn = (EditText) findViewById(R.id.onesIn); 
     fiftyCentsIn = (EditText) findViewById(R.id.fiftyCentIn);
     twentyCentsIn = (EditText) findViewById(R.id.twentyCentIn);
     tenCentsIn = (EditText) findViewById(R.id.tenCentIn);


    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");
    //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());
     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());

 }

}

并给我这样的错误日志 - 

 09-03 15:20:55.083: E/Trace(6712): error opening trace file: No such file or directory (2)
 09-03 15:21:14.753: W/dalvikvm(6712): threadid=1: thread exiting with uncaught exception (group=0x40d59378)
 09-03 15:21:14.763: E/AndroidRuntime(6712): FATAL EXCEPTION: main
 09-03 15:21:14.763: E/AndroidRuntime(6712): java.lang.NullPointerException
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at com.example.tillcounter.TillCounter.onClick(TillCounter.java:68)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.view.View.performClick(View.java:4147)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.view.View$PerformClick.run(View.java:17161)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.os.Handler.handleCallback(Handler.java:615)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.os.Handler.dispatchMessage(Handler.java:92)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.os.Looper.loop(Looper.java:213)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at android.app.ActivityThread.main(ActivityThread.java:4787)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at java.lang.reflect.Method.invokeNative(Native Method)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at java.lang.reflect.Method.invoke(Method.java:511)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
 09-03 15:21:14.763: E/AndroidRuntime(6712):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
09-03 15:21:14.763: E/AndroidRuntime(6712):     at dalvik.system.NativeStart.main(Native Method)

4 个答案:

答案 0 :(得分：1)

在设置好布局后，您应首先引用所有EditText，setContentView。 然后写完所有代码。

代码应该

@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
}

答案 1 :(得分：0)

很简单。您尝试在活动显示在屏幕上之前获取值。

点击这一行

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，而不是之前。

答案 2 :(得分：0)

就像初始化了TextView resultOut一样，你也应该初始化你正在使用的EditTexts来获取用户的输入，例如readingIn = (EditText) findViewById(R.id.your_edit_text)。同样，在分配值时，readingIn值为null。您可以在方法中分配所有值，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
 }

}

答案 3 :(得分：0)

你没有初始化为

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

然后你需要写在OnCreate活动

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