Android: ViewGroup.MarginLayoutParams not working

Question

I used this to set the margin programmatically, but it does not work, the margins are not applied. In the constructor:

public TimeWindow(Context context, int pixels, int left, int top){
    super(context);
    ViewGroup.MarginLayoutParams params = new ViewGroup.MarginLayoutParams(pixels, pixels);
    params.setMargins(left, top, 0, 0);
    this.setLayoutParams(params);
}

Answer 1

Deducing from your comments, you're setting your params when your View does not have LayoutParams yet, and they are being overwritten when you attach your View to the layout. What I would advice you to do is to move the setting of your LayoutParams to the onAttachedToWindow method. Then you will be able to obtain LayoutParams with getLayoutParams() and modify them.

private final int mPixelSize;
private final int mLeftMargin;
private final int mTopMargin;

public TimeWindow(Context context, int pixels, int left, int top){
    super(context);
    mPixelSize = pixels;
    mLeftMargin = left;
    mTopMargin = top;
}

@Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    if (getLayoutParams() instanceof MarginLayoutParams){ 
        //if getLayoutParams() returns null, the if condition will be false
        MarginLayoutParams layoutParams = (MarginLayoutParams) getLayoutParams();
        layoutParams.width = mPixelSize;
        layoutParams.height = mPixelSize;
        layoutParams.setMargins(mLeftMargin, mTopMargin, 0, 0);
        requestLayout();
    }
}