Use "ENTER" key on softkeyboard instead of clicking button

You do it by setting a OnKeyListener on your EditText.

Here is a sample from my own code. I have an EditText named addCourseText, which will call the function addCourseFromTextBox when either the enter key or the d-pad is clicked.

addCourseText = (EditText) findViewById(R.id.clEtAddCourse);
addCourseText.setOnKeyListener(new OnKeyListener()
{
    public boolean onKey(View v, int keyCode, KeyEvent event)
    {
        if (event.getAction() == KeyEvent.ACTION_DOWN)
        {
            switch (keyCode)
            {
                case KeyEvent.KEYCODE_DPAD_CENTER:
                case KeyEvent.KEYCODE_ENTER:
                    addCourseFromTextBox();
                    return true;
                default:
                    break;
            }
        }
        return false;
    }
});

add an attribute to the EditText like android:imeOptions="actionSearch"

this is the best way to do the function

and the imeOptions also have some other values like "go" 、"next"、"done" etc.

may be you could add a attribute to your EditText like this:

android:imeOptions="actionSearch"

<EditText
    android:id="@+id/search"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:hint="@string/search_hint"
    android:inputType="text"
    android:imeOptions="actionSend" />

You can then listen for presses on the action button by defining a TextView.OnEditorActionListener for the EditText element. In your listener, respond to the appropriate IME action ID defined in the EditorInfo class, such as IME_ACTION_SEND. For example:

EditText editText = (EditText) findViewById(R.id.search);
editText.setOnEditorActionListener(new OnEditorActionListener() {
    @Override
    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
        boolean handled = false;
        if (actionId == EditorInfo.IME_ACTION_SEND) {
            sendMessage();
            handled = true;
        }
        return handled;
    }
});

Source: https://developer.android.com/training/keyboard-input/style.html