CODEWITHSUNDEEP
androidmultithreadingtimesleepdelay
Cistoran
Cistoran

Reputation: 1597

Time Delay In Android

So I am trying to create a "strobe" light effect in my app.

To do this I need a time delay, one of 100ms the other of 20.

Here is the code I'm using.

Thread timer = new Thread();
    long longTime = 100;
    long shortTime = 20;
    for (int x = 0; x < 2000000; x++)
    {
        layout.setBackgroundColor(background);
        try {
            timer.sleep(longTime);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        layout.setBackgroundColor(backgroundBlack);
        try {
            timer.sleep(shortTime);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

The issue I have is that when I click the button to call that code, nothing happens. So I've done a bit of debugging and am pretty sure it is the timing call. I have never programmed in Java before so I am unsure how to call a Thread Sleep.

Upvotes: 3

Views: 5297

Answers (3)

rochdev
rochdev

Reputation: 3855

You could use a Handler as below to achieve this. 

public class Strobe extends Activity {

    private LinearLayout mLinearLayout;

    private Handler mHander = new Handler();

    private boolean mActive = false;
    private boolean mSwap = true;   

    private final Runnable mRunnable = new Runnable() {

        public void run() {         
            if (mActive) {
                if (mSwap) {                    
                    mLinearLayout.setBackgroundColor(Color.WHITE);
                    mSwap = false;
                    mHander.postDelayed(mRunnable, 20);
                } else {
                    mLinearLayout.setBackgroundColor(Color.BLACK);
                    mSwap = true;
                    mHander.postDelayed(mRunnable, 100);
                }
            }           
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mLinearLayout = (LinearLayout) findViewById(R.id.strobe);
        startStrobe();
    }

    private void startStrobe() {        
        mActive = true;
        mHander.post(mRunnable);
    }
}

Set a Theme to the Activity to make it full screen.

android:theme="@android:style/Theme.NoTitleBar.Fullscreen"

Upvotes: 4

Zhehao Mao
Zhehao Mao

Reputation: 1789

Your problem is that you are not running in the Thread. In order to run code in the thread you must override it's run() method. Based on your current code, the following may capture what you want to do.

Thread timer = new Thread(){
    public void run(){
        long longTime = 100;
        long shortTime = 20;
        for (int x = 0; x < 2000000; x++)
        {
            layout.setBackgroundColor(background);
            try {
                Thread.sleep(longTime);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            layout.setBackgroundColor(backgroundBlack);
            try {
                Thread.sleep(shortTime);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

timer.start();

However, threads don't play that well with the Android OS. For your application, it may be better to use Android services. See http://developer.android.com/guide/topics/fundamentals/services.html .

Upvotes: 1

BobMcboberson
BobMcboberson

Reputation: 2065

I think this article would benefit you. http://oreilly.com/catalog/expjava/excerpt/index.html specifically this http://oreilly.com/catalog/expjava/excerpt/index.html#EXJ-CH-6-FIG-1

Upvotes: 1

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