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My first Google Android Java application
 
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Author Message
WauloK
Developer


Joined: 19 Dec 2007
Posts: 30
Location: Brisbane, Australia
PostPosted: Sat Feb 09, 2008 1:20 pm    Post subject: My first Google Android Java application Reply with quote
Over the last two days I've been working on a small calculations application.
Today I finally finished it! Very Happy
It's late at the moment so I will soon be uploading information on it.
I hope to put lots of info and descriptions to help people learn from it, on my website in my signature.

For now, here's a sneak preview Wink

BestValue_screenshot.png
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AndroidChi - Applications for the Google Android platform.
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WauloK
Developer


Joined: 19 Dec 2007
Posts: 30
Location: Brisbane, Australia
PostPosted: Tue Feb 12, 2008 11:40 pm    Post subject: Reply with quote
Since my forum is having issues posting code I will paste my application source here for others to use.

BestValue.java:
Java:
package com.androidchi.bestvalue;

// Import all the required packages
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

// Main program begins here..
public class BestValue extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);
       
        // Listen for button clicks
        Button calcbutton=(Button)findViewById(R.id.calc);
        Button clearbutton=(Button)findViewById(R.id.clear);
        Button aboutbutton=(Button)findViewById(R.id.about);        

        // Code for calc button
        if (calcbutton != null) {
          // Listen for the button being hit
          calcbutton.setOnClickListener(new OnClickListener() {
               public void onClick(View viewParam) {
                    // Find the EditText (where the user can type) that we defined in main.xml
                    EditText price1EditText = (EditText)findViewById(R.id.price1);
                    EditText units1EditText = (EditText)findViewById(R.id.units1);
                    EditText price2EditText = (EditText)findViewById(R.id.price2);
                    EditText units2EditText = (EditText)findViewById(R.id.units2);                       
                    // Make sure the text boxes actually exist
                    if ((price1EditText == null) || (units1EditText == null) || (price2EditText == null) ||
                              (units2EditText == null))
                         {
                              showAlert("Error",0,"Couldn't find one of the text entry EditViews in main.xml","Okay", false);
                         }
                    // Make sure the boxes actually contain numbers to calculate with
                    else if (price1EditText.getText().toString().equals("") || price2EditText.getText().toString().equals("") || units1EditText.getText().toString().equals("") || units2EditText.getText().toString().equals("")) {
                         showAlert("Error",0,"Text boxes may not be left empty!","Okay", false);
                    }
                    else {
                         // If they do, convert the entered Strings to actual numbers for calculating with
                    double price1=Double.parseDouble(price1EditText.getText().toString());
                    double price2=Double.parseDouble(price2EditText.getText().toString());
                    double units1=Double.parseDouble(units1EditText.getText().toString());
                    double units2=Double.parseDouble(units2EditText.getText().toString());
                    
                    // Make sure they aren't dividing by zero!
                    if ( Double.compare(units1, 0.0) == 0 || Double.compare(units2, 0.0) == 0 ) {
                         showAlert("Error",0,"Quantities may not be zero.","Okay", false);
                    } else {
                         // Calculate the values of units per price
                         double value1=(price1/units1);
                         double value2=(price2/units2);
                    
                         // Find the ID of the "result" text field to write results in
                         TextView result=(TextView)findViewById(R.id.result);
                         TextView values=(TextView)findViewById(R.id.valuestext);
                    
                         values.setText("Value #1: " + String.format("%.02f",  value1) + " and Value #2: "+ String.format("%.02f",  value2));
                    
                         // Is value1 the cheapest?
                         if (value1 < value2) {
                              result.setText(getString(R.string.valuebest1));
                         }
                         // Is value2 the cheapest?
                         else if (value2 < value1) {
                              result.setText(getString(R.string.valuebest2));
                         }
                         // They are both the same price per unit
                         else {
                              result.setText(getString(R.string.valuesequal));
                         }
                    }
                         }
                    }
               });            
          }
        // clear button hit
        if (clearbutton != null) {
          clearbutton.setOnClickListener(new OnClickListener() {
               public void onClick(View viewParam) {
                    // find the text boxes
                    EditText price1EditText = (EditText)findViewById(R.id.price1);
                    EditText units1EditText = (EditText)findViewById(R.id.units1);
                    EditText price2EditText = (EditText)findViewById(R.id.price2);
                    EditText units2EditText = (EditText)findViewById(R.id.units2);
                    
                    if ((price1EditText == null) || (units1EditText == null) || (price2EditText == null) ||
                              (units2EditText == null)) {
                         showAlert("Error",0,"Couldn't find one of the text entry EditViews in main.xml","Oops", false); }
                    else {
                         // Find out where result and values text boxes are
                         TextView result=(TextView)findViewById(R.id.result);
                         TextView valuestext=(TextView)findViewById(R.id.valuestext);  
                         // Clear entries in price and units text boxes
                         price1EditText.setText("");
                         units1EditText.setText("");
                         price2EditText.setText("");
                         units2EditText.setText("");
                         // Clear the 'result' text output as well as each text box
                         result.setText("");
                         valuestext.setText("");
                         // Set focus to Price 1 EditText box (put cursor there)
                         price1EditText.requestFocus();
                    }
               }
          });
        }
        // About button hit
        if (aboutbutton != null) {
          aboutbutton.setOnClickListener(new OnClickListener() {
               public void onClick(View viewParam) {
                    // Pop up a window with some info and a button to make it go away
                    showAlert("Best Value by Jason Oakley",0, getString(R.string.abouttext), "Okay, Thanks!", false);
               }
               
          });
        }
     }
}


STRINGS.XML:
XML:
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Best Value</string>
    <string name="app_version">0.1</string>
     <string name="heading">Best Value by AndroidChi.com</string>
     
    <string name="price1"></string>
    <string name="units1"></string>
    <string name="price2"></string>
    <string name="units2"></string>

    <string name="textprice1">Price #1 :</string>
    <string name="textunits1">Qty #1 :</string>
    <string name="textprice2">Price #2 :</string>
    <string name="textunits2">Qty #2 :</string>
   
    <string name="calc">Calc</string>
    <string name="clear">Clear</string>
    <string name="about">About</string>    
   
    <string name="valuebest1">Item #1 is the Best Value!</string>
     <string name="valuebest2">Item #2 is the Best Value!</string>
     <string name="valuesequal">Both have the same value!</string>
    <string name="result"></string>
    <string name="resulttext">Result: </string>   
    <string name="valuestext"></string>
   
    <string name="abouttext">Enter two prices and two quantity amounts and Best Value will tell you which price gives the best value for your money. Visit www.AndroidChi.com for more Android applications!</string>     
</resources>


MAIN.XML:
XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
          <TextView android:id="@+id/heading"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:text="@string/heading"
          android:textStyle="bold"
          android:textAlign="center"
          />

        <TextView android:id="@+id/textprice1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textprice1"
            android:layout_below="@id/heading"
            android:layout_marginTop="13px"            
            />
        <EditText android:id="@+id/price1"
            android:layout_width="100px"
            android:layout_height="wrap_content"
            android:layout_toRight="@id/textprice1"
            android:layout_below="@id/heading"  
            android:layout_marginTop="10px"
            android:layout_marginLeft="5px"                                  
            android:numeric="true"
            android:digits="0123456789."
            android:text=""
            />
        <TextView android:id="@+id/textunits1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textunits1"
            android:layout_below="@id/textprice1"
            android:layout_marginTop="13px"
            android:layout_marginLeft="9px"              
            />
        <EditText android:id="@+id/units1"
            android:layout_width="100px"
            android:layout_height="wrap_content"
            android:layout_toRight="@id/textunits1"
            android:layout_below="@id/textprice1"  
            android:layout_marginTop="10px"
            android:layout_marginLeft="5px"                    
            android:numeric="true"
            android:text=""
            />
        <TextView android:id="@+id/textprice2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textprice2"
            android:layout_below="@id/textunits1"
            android:layout_marginTop="13px"  
            />
        <EditText android:id="@+id/price2"
            android:layout_width="100px"
            android:layout_height="wrap_content"
            android:layout_toRight="@id/textprice2"
            android:layout_below="@id/textunits1"  
            android:layout_marginTop="10px"
            android:layout_marginLeft="5px"                      
            android:numeric="true"
            android:digits="0123456789."            
            android:text=""
            />            
        <TextView android:id="@+id/textunits2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textunits2"
            android:layout_below="@id/textprice2"
            android:layout_marginTop="13px"
            android:layout_marginLeft="9px"              
            />
        <EditText android:id="@+id/units2"
            android:layout_width="100px"
            android:layout_height="wrap_content"
            android:layout_toRight="@id/textprice2"
            android:layout_below="@id/textprice2"  
            android:layout_marginTop="10px"  
            android:layout_marginLeft="5px"                                
            android:numeric="true"
            android:text=""
            />                  
        <Button android:id="@+id/calc"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/calc"
            android:layout_below="@id/textunits2"
            android:layout_marginTop="13px"
            android:layout_marginLeft="0px"  
            />
        <Button android:id="@+id/clear"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/clear"
            android:layout_toRight="@id/calc"
            android:layout_marginTop="0px"
            android:layout_alignTop="@id/calc"  
            android:layout_marginLeft="5px"
            />      
        <Button android:id="@+id/about"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/about"
            android:layout_toRight="@id/clear"
            android:layout_marginTop="0px"
            android:layout_alignTop="@id/calc"  
            android:layout_marginLeft="5px"
            />
         <TextView android:id="@+id/valuestext"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/valuestext"
            android:layout_below="@id/calc"
            android:layout_marginTop="13px"              
            />                              
        <TextView android:id="@+id/resulttext"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/resulttext"
            android:layout_below="@id/valuestext"
            android:layout_marginTop="13px"  
            />
        <TextView android:id="@+id/result"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/valuestext"            
            android:layout_toRight="@id/resulttext"            
            android:text=""
            android:layout_marginTop="13px"
            android:layout_marginLeft="5px"                        
            />
</RelativeLayout>


If any experienced Java programmers have suggestions, please let me know Smile
_________________
AndroidChi - Applications for the Google Android platform.

Last edited by WauloK on Tue Feb 19, 2008 11:53 am; edited 1 time in total
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plusminus
Site Admin


Joined: 14 Nov 2007
Posts: 2067
Location: Germany
PostPosted: Tue Feb 12, 2008 11:58 pm    Post subject: Reply with quote
Hello waulok,

thanks for sharing Smile

I myself never check if the Views were actually found from XML, I just assume it Rolling Eyes
If they don't I receive a NullPointerException what foces me to review the code.

Regards,
plusminus
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WauloK
Developer


Joined: 19 Dec 2007
Posts: 30
Location: Brisbane, Australia
PostPosted: Tue Feb 19, 2008 11:54 am    Post subject: Reply with quote
Updated for the new SDK! Smile
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