Develop Reference

How to make a textbox appear when turning off a Smartphone?

I'm writing a simple app for Android. It's very simple yet, it just take as input a username and a password.
I need to store those user and pwd firstly, then I need to make a textbox asking for those user and password appear when I try to turn off the smartphone.
Could you please help me on how to do it?

There is no way to do this reliably. Even if there was a systemwide shutdown message (and I don't think there is), the user could always just pull the battery. Or hold the power button for a few seconds to force a reboot.
Even ignoring that- there's no way to make shutdown wait until a user has entered the info you want. Even if you could display it, it would just go away and the phone would turn off. You'd be looking at a custom android os to do this.

How to make full screen caller id in android?

I Want to develop Full Screen caller application with Caller details and accept call and ignore button how to achieve this? .I searched a lot but i'm not able to find solution or any reference, so anyone can lead or help me or any reference it would be helpful for me, thanks in advance happy coding.

I'm not going to give you ready-made code even though I could probably dig into my own and do it. You said you searched a lot but if this were true, you'd have found many references to articles and docs such as these.
Get contact data from number
Take control of calls programmatically
Detect incoming calls
Interesting considerations for incoming calls
That should get you started. But it should go someting like this: Register that you want to be notified when incoming calls are received. On that notification you receive launch your own activity that takes control of the calls programmatically (button to dismiss, button to accept?). That screen can show whatever you want, beit the contact information you retrieved from the phone number, a photo, etc.

Android Wear - Retrieve value from Phone

I hope someone can help me. I can't seem to find anything that gives me a straight answer or that works.
So basically on my Phone app the user enters their age which I will then save and pass to the Watch.
For now to get it working i'm just using a hardcoded int value.
So what I want the watch to do is when the user enters a certain activity on the watch that it will retrieve this value each time from the phone and be displayed.
Obviously I intend to do more than just display it but if I could get it displaying first it would mean that its being retrieved.
Can anyone help me? Thanks in advance.

Take a look at http://developer.android.com/training/wearables/data-layer/index.html and choose accordingly to your context the appropriate API(s).

In said activity on the watch, implement GoogleApiClient. In the onConnected() method send a message to your phone via Wearable.MessageApi.sendMessage Assuming you want to retrieve this information from the phone while the app is not open on the phone, use a WearableListenerService on the phone to receive the message. Now you have successfully told the phone you want info! Simple gather the info you need while still in the WearableListenerService and send another message back to the watch via Wearable.MessageApi.sendMessage
Let me know if you have any more questions

How to hide caller ID info like phone number on receiver side phone replaceing with some text in android?

In my application,I want to make appear some text like "Private Number" on receiver side cell on caller Id instead of phone number,so that receiver should not know the phone number where he/she is getting call from.
I researched a lot, but I couldn't find exact way to do this.
Can anyone help me,I will be thankful.

If You Have Android Phone Then You Must Try This Out:
Go to Settings.
Call settings
Additional settings
Wait until it initializes the options
Caller ID
Hide number
Go back and you're done

Android: How to capture button press event for contact create app of device

I want to invoke my application once user creates / updates contact from his device.
i.e once user hit "Done" button. is it possible ? If possible please provide sample code or link.
Please help and thanks in advance.

I want to invoke my application once
user creates / updates contact from
his device. i.e once user hit "Done"
button. is it possible ?
No, it is not possible, in terms of detecting the GUI event. You can set up a data observer on the Contacts (or ContactsContract) content provider, and attempt to find out those things that way, though I do not know how well that works.