Android Toggle button

Question

I am a beginner to Android development and am trying to make an application whose requirement is to display random number in a text box, and continue to display the random numbers with one second or any programmable delay, till the time the toggle button is in 'ON' state. Does anyone have suggestion on it, or if possible sharing a partial source code would be good.

Another suggestion that I would require is regarding any good book to start off with android development with its internal details also. If there is any sort of book on android as that we have for other development languages (ex. Complete Reference to Java, Complete Reference to C, C++ etc)

Thanks in advance

Answer 1

I have read some Andoid books and I strongly suggest Android in Practice. After you have read it, you'll know that the majority of people asking questions here on StackOverflow would substantially benefit from this book alone. It's excellent price-value and the authors definitely knew what they were writing about.

Edit: Regarding the implementation (UPDATED, eliminated boolean)

public final class MyActivity extends Activity implements Runnable {
    private Handler uiThreadHandler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // basics
        super.onCreate(savedInstanceState);
        setContentView(R.layout.your_activity_layout);
        // find text widget here, store in editText as also required in Chintan's solution
        // get the current activity's handler, it's the UI thread
        uiThreadHandler = new Handler();
        // initiate the updates if that's the initial state
        scheduletUpdate();
        // register callbacks for button etc as required also in Chintan's solution
    }
    @Override
    public void run() {
        //update your editText field here -- this is run in the UI thread so it's safe!
        scheduleUpdate();
    }
    private void scheduleUpdate() {
        uiThreadHandler.postDelayed(this, 1000); // 1000 ms
    }
    // etc, some stuff missing
}

Edit: Regarding how to stop the scheduling of executing the run() method, you use the following code, which should be obvious from the Handler documentation (UPDATED, eliminated boolean):

uiThreadHandler.removeCallbacks(this);

Answer 2

As a beginner, I would suggest you to go through http://www.mybringback.com/series/android-basics/ this tutorials and you will be able to do what you have asked by yourselves. They also have easy to follow video tutorials.

Answer 3

Use Thread like,

class MyThread extends Thread
{
    private volatile boolean isRunning = false;

    public synchronized void requestStop() {
        isRunning = true;
    }

    @Override
    public void run() {
        //place code here...
        try {
            while (!isRunning) {
                // do your coding
                handler.sendMessage(handler.obtainMessage(WhatAbout.CHANGE_TEXT.ordinal(), 0, 0));
                Thread.sleep(1000 * 1); //1000 ms = 1 sec
            }


        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Now define following code to handle multiple messages.

public enum WhatAbout {
    CHANGE_TEXT
}

public WhatAbout[] wa = WhatAbout.values();

Then use [Handler][1], which helps you to communicate BackgroundThread and UIThread. Without using handler, you can't change UI.

Put following code in your onCreate method.

handler = new Handler() {
  @Override
  public void handleMessage(Message msg) {
    if (msg.what < wa.length) {
    switch (wa[msg.what]) 
    {
    case CHANGE_TEXT:
         editText.setText(randomVariable);
         break;
    }
  }
};

When you toggle switch off, use following code to stop thread.

if (thread != null) {
    thread .requestStop();
    thread = null;
}