Android-可见和不可见按钮

Question

I am trying to get a button to become visible if there is one or more objects in an array, otherwise it will stay invisible.

I am used:

if (positionOverlay.geoPointsArrayList.size() <= 0){
    buttonClear.setVisibility(View.GONE);
    System.out.println("Clear button hidden");
}
else if (positionOverlay.geoPointsArrayList.size() >= 1) {
    buttonClear.setVisibility(View.VISIBLE);
    System.out.println("Clear button visible");
}

The problem I am having is that it runs and on start up the array i am using is empty, so the button stays invisible, however when I add objects to the array it still stays invisible, suggesting that it doesnt run the code again.

I have placed the code above in the onCreate, could anyone tell me where i have gone wrong?

Answer 1

When you alter your array of objects you'll need to run the code you have in onCreate - what you have now only ever checks on startup and isn't linked to the array being altered at all.

So in pseudocode if you have:

array.add("new item");
this.updateButton(); // This is where you have your button code.

array.remove("some other item");
this.updateButton(); // Check if you've gone below the limit again