Question

I have a problem with soft keyboard backspace in Android (4.2).

I have a custom editor in a WebView (CodeMirror), which uses an empty <textarea> internally. It seems that backspace is not sent by an Android system unless it believes there is some text in the <textarea>.

I have overridden WebView onCreateInputConnection in an attempt to dumb down soft input:

@Override
public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
    Log.d("CustomWebView", "onCreateInputConnection(...)");
    BaseInputConnection connection = new BaseInputConnection(this, false);
    outAttrs.inputType = InputType.TYPE_NULL;
    outAttrs.imeOptions = EditorInfo.IME_ACTION_NONE;
    outAttrs.initialSelStart = -1;
    outAttrs.initialSelEnd = -1;

    return connection;
}

However, this does not work, and even onKeyUp is not called for backspace.

How do I force soft keyboard to always send backspace?

Answer 1

Ok, finally figured this out.

In Android 4.2 (maybe in earlier versions as well) the backspace is not sent as a sendKeyEvent(..., KeyEvent.KEYCODE_DEL) by the standard soft keyboard. Instead, it is sent as deleteSurroundingText(1, 0).

So the solution in my case is to make a custom InputConnection with the following:

@Override
public boolean deleteSurroundingText(int beforeLength, int afterLength) {       
    // magic: in latest Android, deleteSurroundingText(1, 0) will be called for backspace
    if (beforeLength == 1 && afterLength == 0) {
        // backspace
        return super.sendKeyEvent(new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DEL))
            && super.sendKeyEvent(new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_DEL));
    }

    return super.deleteSurroundingText(beforeLength, afterLength);
}

Note: Please let me know if I am doing something stupid here, as it is my 3rd day writing for Android.