In the UI perspective, I have created an Imagebutton to display an icon. Let me explain the code part step by step.

  A quick way to enable taking pictures in your application without a lot of extra code is to use an Intent to invoke an existing Android camera application. A camera intent makes a request to capture a picture or video clip through an existing camera app and then returns control back to your application.

Intent i;
Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

MediaStore - The Media provider contains meta data for all available media on both internal and external storage devices.

ACTION_IMAGE_CAPTURE - Standard intent action that can be sent to capture image through android camera application and return it back.

Step 2:

Now lets start the camera intent, through the method -  startActivityForResult(). Once the intent is started camera application UI appears on the screen and user can take pictures as usual.

startActivityForResult(i, CAPTURE_IMAGE_CAPTURE_CODE);

i - Intent to start

CAPTURE_IMAGE_CAPTURE_CODE  - A constant value (request code), If >= 0, this code will be returned in onActivityResult() when the activity exits.

When this activity exits, your onActivityResult() method will be called with the given requestCode.

Step 3:

The result from the activity will be returned to onActivityResult(int requestCode, int resultCode, Intent data), where we can perform our own functionality to process the result.

requestCode - The request code (CAPTURE_IMAGE_CAPTURE_CODE) that was supplied to startActivityForResult(), using which we can confirm which intent has sent back data.

resultCode - Result code sent back from the intent

data - An Intent, which can return result data to the caller

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
//check which intent has sent back data
   if (requestCode == CAPTURE_IMAGE_CAPTURE_CODE) {
//check whether the process was success
      if (resultCode == RESULT_OK) {
         //perform your own functionality, I have displayed a Toast indication success
         Toast.makeText(this, "Image Captured", Toast.LENGTH_LONG).show();
      } 
//Check if the capture failed and perform your functionality
      else if (resultCode == RESULT_CANCELED) {
         Toast.makeText(this, "Cancelled", Toast.LENGTH_LONG).show();
      }
  }
}

Camera App [img src="Android%20%20Camera%20app%20in%20android%20example%20_%20COMPILETIMEERROR.com_files/screen2.png" border="0" height="133" width="200">

<b><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

      <ImageButton
          android:id="@+id/buttonToast"
          android:layout_width="150dp"
          android:layout_height="150dp"
          android:layout_alignParentTop="true"
          android:layout_centerHorizontal="true"
          android:layout_marginTop="24dp"
          android:contentDescription="@string/selectdate"
          android:cropToPadding="true"
          android:src="@drawable/camera3" />

</RelativeLayout>
</b>