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POAndroid calculator with button click
 

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  1. POAndroid calculator with button click
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    <p>I am trying to calculate a field named lblAnswer by adding values txtA + txtB. I am fairly new to the android development world and would like to know what is the best way of going about this. I have already added the necessarily edit fields to the GUI. I am now working in the java file to try and create the method. This method has been named doCalc. Here is what I have thus far. </p> <pre><code>public void doCalc() { lblAnswer = txtA + txtB; } </code></pre> <p>It has been suggested that I add more code here is the full code. Thank you for that suggestion. </p> <p>Here is the Java File. </p> <pre><code> package com.example.wattsprofessional; import android.app.Activity; import android.os.Bundle; import android.view.Menu; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @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; } public void doCalc() { lblAnswer = txtA + txtB; Double.parseDouble(txtA.getText().toString()); lblAnswer.setText"t } </code></pre> <p>and here is the xml file. </p> <pre><code> &lt;RelativeLayout 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" tools:context=".MainActivity" &gt; &lt;EditText android:id="@+id/txtA" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:layout_marginTop="40dp" android:ems="10" android:hint="Write Here" android:inputType="numberDecimal" &gt; &lt;requestFocus /&gt; &lt;/EditText&gt; &lt;EditText android:id="@+id/txtB" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/txtA" android:layout_below="@+id/txtA" android:layout_marginTop="32dp" android:ems="10" android:hint="Second Here" android:inputType="numberDecimal" /&gt; &lt;Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_centerVertical="true" android:text="@string/calculate" android:onClick="doCalc"/&gt; &lt;TextView android:id="@+id/lblAnswer" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/button1" android:layout_centerHorizontal="true" android:layout_marginTop="50dp" android:text="TextView" /&gt; &lt;/RelativeLayout&gt; </code></pre>
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    1. COwhat problems are you having exactly? for all we know things are going well without a hitch. I can't give you a *best* way, but what i'd do is make all my calculations separate methods that take parameters and then return a value.
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      1. USmango
    2. COthank you for the quick reply. Well when I look at the actual method you see above, the lblAnswer = txtA + txtB; has an error line underneath it. It states " Cannot be resolved to a variable" This is the error message for all three. I'm not sure where I am messing up .
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      1. USRyan Watts
    3. COYou need to declare them as global variables, then initialize them in `onCreate()`.
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      1. USTechwolf
 

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