CODEWITHSUNDEEP
javablackberry
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Reputation: 877

how to read from a txt file in blackberry eclipse?

i am developing an simple blackberry application in BlackBerry - Java Plug-in for Eclipse. In that, i want to read data from an external text file. I had searched for this, and tried for some tips, like. But failed at last. I will describe my application...

my main file...

package com.nuc;

import net.rim.device.api.ui.UiApplication;
public class Launcher extends UiApplication
{
    public static void main(String[] args)
    {
        Launcher theApp = new Launcher();       
        theApp.enterEventDispatcher();
    }

    public Launcher()
    {        
        pushScreen(new MyScreen());
    }    
}

And then my app class is like....

package com.nuc;

import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.component.BasicEditField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.EditField;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.container.GridFieldManager;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;

public final class MyScreen extends MainScreen implements FieldChangeListener
{
// declared variables...
    public MyScreen()
    {     
      //rest codes...

I want to show some details from a text file before my app starts, like the End User License Agreement.. ie, something which cames as the first line..

my first question is, where i need to put that text file... i got lots of guidance from net, but nothing worked for eclipse.. Secondly, then how can i read the file and put its content in a dialog.

So plz guide me how i can achieve it.. sample code will be appreciable, for i am new to this environment...

Upvotes: 1

Views: 1342

Answers (2)

javajavajavajavajava
javajavajavajavajava

Reputation: 1233

Rupak's answer is mostly correct, but there's a few problems with it. You definitely don't want to add immutable strings together in a situation like this. When you add 2 strings together (myString += "Another String") Java basically creates a new String object with the values of the two other Strings, because it cannot change the contents of the other strings. Usually this is fine if you just need to add two strings together, but in this case if you have a large file then you're creating a new String object for EVERY character in the file (each object bigger than the last). There's a lot of overhead associated with this object creation AND the garbage collector (very slow) will have to intervene more often because of all these objects that need to be destroyed.

StringBuffer to the rescue! Using a StringBuffer in place of the String concatenation will only require 1 object to be created and will be much faster.

try {
    InputStream is = (InputStream) getClass().getResourceAsStream("/Text");
    StringBuffer str = new StringBuffer();            
    int ch;
    while ((ch = is.read()) != -1) {
        str.append((char)ch);
    }
    UiApplication.getUiApplication().invokeLater(new Runnable(){
        public void run(){
            Dialog.alert(str.toString() == null ? "Failed to read." : str.toString());
        }
    }
} catch (Exception e) {
    UiApplication.getUiApplication().invokeLater(new Runnable(){
        public void run(){
            Dialog.alert(e.getMessage() + " + " + e.toString());
        }
    }
}

Also several developers on the Blackberry support forums recommend against using UiApplication.getEventLock() because it can be "dangerous". They recommend using invokeLater() instead. See Blackberry Support Forums

Upvotes: 1

Rupak
Rupak

Reputation: 3674

To add a file to your Eclipe project

  • right click on the res folder of your project structure, click on New, click on Untitled Text File and then enter some text and save the file.

To read from a file and display on a dialog try something like the following code snippet:

try {
    InputStream is = (InputStream) getClass().getResourceAsStream("/Text");
    String str = "";            
    int ch;
    while ((ch = is.read()) != -1) {
        str += (char)ch;
    }
    synchronized (UiApplication.getEventLock()) {
        Dialog.alert(str == null ? "Failed to read." : str);    
    }
} catch (Exception e) {
    synchronized (UiApplication.getEventLock()) {
        Dialog.alert(e.getMessage() + " + " + e.toString());
    }
}

in the above code "/Text" is the file name. And if you got a NullPointerException then check the file name and path.

Upvotes: 2

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