Try this..

Change this..

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                        getApplicationContext());

to

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                        AlarmActivity.this);

EDIT

radio_btn.xml

<?xml version="1.0" encoding="UTF-8"?>
<RadioGroup xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/status_group"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:orientation="vertical" >

    <RadioButton
        android:id="@+id/default_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Default music" />

    <RadioButton
        android:id="@+id/external_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="External card music" />

</RadioGroup>

JAVa

    LayoutInflater inflater = getLayoutInflater();
    View dialoglayout = inflater.inflate(R.layout.radio_btn, (ViewGroup) getCurrentFocus());
    RadioButton default_btn = (RadioButton) dialoglayout.findViewById(R.id.default_btn);
    RadioButton external_btn = (RadioButton) dialoglayout.findViewById(R.id.external_btn);
    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                        AlarmActivity.this);
                Log.d("TAG","button inside mobile");
                alertDialogBuilder
                //.setMessage("Click yes to exit!")
                .setCancelable(false)
                .setView(dialoglayout);
                .setPositiveButton("OK",new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog,int id) {
                        // if this button is clicked, close
                        // current activity
                        AlarmActivity.this.finish();
                    }
                  });
                 alertDialogBuilder.show();

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You should try to override the Back Key hardware, and handle the expected behaviour with a boolean as follows:

// boolean isVisible to retrieve the state of the SoftKeyboard
private boolean isVisible = false;

// isVisible becomes 'true' if the user clicks on EditText

// then, if the user press the back key hardware, handle it:
@Override
public boolean onKeyPreIme(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        // check isVisible
        if(isVisible) {
            // hide the keyboard
            InputMethodManager mImm = (InputMethodManager) mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
            mImm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
            isVisible = false;
        } else {
            // remove the CAB
            mActionMode.finish();
        }
    }
    return false;
}  

Another solution might be to call dispatchKeyEvent method which is still called when the CAB is displayed:

@Override
public boolean dispatchKeyEvent(KeyEvent event) {
    if (event.getKeyCode() == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
        // check CAB active and isVisible softkeyboard
        if(mActionModeIsActive && isVisible) {
            InputMethodManager mImm = (InputMethodManager) mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
            mImm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
            isVisible = false;
            return true;
        // Maybe you might do not call the 'else' condition, anyway..
        } else {
            mActionMode.finish();
            return true;
        }
    }
    return super.dispatchKeyEvent(event);
}  

This should do the trick, but I have not tested it. Hope this helps.
Sources: How to Override android's back key when softkeyboard is open - Prevent to cancel Action Mode by press back button

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You should try to override the Back Key hardware, and handle the expected behaviour with a boolean as follows:

// boolean isVisible to retrieve the state of the SoftKeyboard
private boolean isVisible = false;

// isVisible becomes 'true' if the user clicks on EditText

// then, if the user press the back key hardware, handle it:
@Override
public boolean onKeyPreIme(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        // check isVisible
        if(isVisible) {
            // hide the keyboard
            InputMethodManager mImm = (InputMethodManager) mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
            mImm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
            isVisible = false;
        } else {
            // remove the CAB
            mActionMode.finish();
        }
    }
    return false;
}  

Another solution might be to call dispatchKeyEvent method which is still called when the CAB is displayed:

@Override
public boolean dispatchKeyEvent(KeyEvent event) {
    if (event.getKeyCode() == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
        // check CAB active and isVisible softkeyboard
        if(mActionModeIsActive && isVisible) {
            InputMethodManager mImm = (InputMethodManager) mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
            mImm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
            isVisible = false;
            return true;
        // Maybe you might do not call the 'else' condition, anyway..
        } else {
            mActionMode.finish();
            return true;
        }
    }
    return super.dispatchKeyEvent(event);
}  

This should do the trick, but I have not tested it. Hope this helps.
Sources: How to Override android's back key when softkeyboard is open - Prevent to cancel Action Mode by press back button

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You can lose focus by doing the following:

searchView.clearFocus();

You can also force hiding the keyboard on any event you want with the inputManager.

For example:

InputMethodManager inputManager = (InputMethodManager) this
            .getSystemService(Context.INPUT_METHOD_SERVICE);

    //check if no view has focus:
    View v=this.getCurrentFocus();
    if(v==null)
        return;

    inputManager.hideSoftInputFromWindow(v.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);

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Try this

private void showKeyboard(View view) {
    InputMethodManager keyboard = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
    keyboard.showSoftInput(view, 0);
}

private void hideKeyboard() {
    InputMethodManager inputMethodManager = (InputMethodManager) this
            .getSystemService(Context.INPUT_METHOD_SERVICE);
    inputMethodManager.hideSoftInputFromWindow(this.getCurrentFocus()
            .getWindowToken(), 0);
}

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