Andrey Shchekin Andrey Shchekin - 10 months ago 165
Android Question

Android: Backspace in WebView/BaseInputConnection

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

internally. It seems that backspace is not sent by an Android system unless it believes there is some text in the

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

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
is not called for backspace.

How do I force soft keyboard to always send backspace?

Answer Source

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:

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.