问题
I know how to draw an object arrow on the chart, which I usually do like this:
ObjectCreate(0,"prevHigh",OBJ_ARROW_DOWN,0,Time[0],High[highestCandle]);
ObjectSetInteger(0, "prevHigh", OBJPROP_COLOR, clrRed);
Now I have an indicator which (I didn't code myself and is a .ex4 file which) draws up/down arrows on the chart as seen in the image (https://imgur.com/a/8yG0suw).
How can I when for example a Magenta down arrow has been drawn and the candle (index) at which it is drawn?
Please note that the arrows not in the list of objects on the chart
回答1:
Q : "How can I recognise programmatically when an up/down arrow is drawn on a chart?"
Given the facts above, your test ought evaluate the moment the CustomIndicator ( via a published / used iCustom()-call signature ) by checking it as it goes from EMPTY_VALUE to any value != EMPTY_VALUE.
Given the CustomIndicator is a closed source ( *.ex4 ) you may need to check, if it did set its own ( hidden from our sight ) value, other than a current visible EMPTY_VALUE, yet this "re-calibration" will work, after you get a few manual tests of the CustomIndicator values for bars, that do not show any arrow - like for the 2020-Apr-08 09:30 et al v/s the displayed arrows are not the MQL4-Objects on their own, they are the closed-source CustomIndicator's SetIndexStyle() / SetIndexArrow() by-products, thus not inspectable either in the Object-List, or in the *.mq4 source-code.
Yet, detectable
来源：https://stackoverflow.com/questions/61132974/how-can-i-recognise-programmatically-when-an-up-down-arrow-is-drawn-on-a-chart-w