Android按键拦截处理最佳实践范例（以Back事件为例）

1. 想拦截所有情况下的按键：

   @Override
       public boolean dispatchKeyEventPreIme(KeyEvent event)
       {
           if (event.getAction() == KeyEvent.ACTION_DOWN//
                   && event.getKeyCode() == KeyEvent.KEYCODE_BACK)
           {
               // doSth...
               return true;
           }
   
           return super.dispatchKeyEventPreIme(event);
       }

2. 想处理子View不处理的按键：

    @Override
    public boolean dispatchKeyEvent(KeyEvent event)
    {
        boolean handled = super.dispatchKeyEvent(event);

        if (!handled)
        {
            if (event.getAction() == KeyEvent.ACTION_DOWN//
                    && event.getKeyCode() == KeyEvent.KEYCODE_BACK)
            {
                // doSth...
                return true;
            }
        }
        return handled;
    }

3.想禁止IME处理，但只处理子View不处理的按键：

@Override
    public boolean dispatchKeyEventPreIme(KeyEvent event)
    {
        if (event.getAction() == KeyEvent.ACTION_DOWN//
                && event.getKeyCode() == KeyEvent.KEYCODE_BACK)
        {
            return false;
        }

        return super.dispatchKeyEventPreIme(event);
    }

    @Override
    public boolean dispatchKeyEvent(KeyEvent event)
    {
        boolean handled = super.dispatchKeyEvent(event);

        if (!handled)
        {
            if (event.getAction() == KeyEvent.ACTION_DOWN//
                    && event.getKeyCode() == KeyEvent.KEYCODE_BACK)
            {
                // doSth...
                return true;
            }
        }
        return handled;
    }