In Android, how do I set margins in dp programmatically?


Answers

LayoutParams - NOT WORKING ! ! !

Need use type of: MarginLayoutParams

MarginLayoutParams params = (MarginLayoutParams) vector8.getLayoutParams();
params.width = 200; params.leftMargin = 100; params.topMargin = 200;

Code Example for MarginLayoutParams:

http://www.codota.com/android/classes/android.view.ViewGroup.MarginLayoutParams

Question

In this, this and this thread I tried to find an answer on how to set the margins on a single view. However, I was wondering if there isn't an easier way. I'll explain why I rather wouldn't want to use this approach:

I have a custom Button which extends Button. If the background is set to something else than the default background (by calling either setBackgroundResource(int id) or setBackgroundDrawable(Drawable d)), I want the margins to be 0. If I call this:

public void setBackgroundToDefault() {
    backgroundIsDefault = true;
    super.setBackgroundResource(android.R.drawable.btn_default);
    // Set margins somehow
}

I want the margins to reset to -3dp (I already read here how to convert from pixels to dp, so once I know how to set margins in px, I can manage the conversion myself). But since this is called in the CustomButton class, the parent can vary from LinearLayout to TableLayout, and I'd rather not have him get his parent and check the instanceof that parent. That'll also be quite inperformant, I imagine.

Also, when calling (using LayoutParams) parentLayout.addView(myCustomButton, newParams), I don't know if this adds it to the correct position (haven't tried however), say the middle button of a row of five.

Question: Is there any easier way to set the margin of a single Button programmatically besides using LayoutParams?

EDIT: I know of the LayoutParams way, but I'd like a solution that avoids handling each different container type:

ViewGroup.LayoutParams p = this.getLayoutParams();
    if (p instanceof LinearLayout.LayoutParams) {
        LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams)p;
        if (_default) lp.setMargins(mc.oml, mc.omt, mc.omr, mc.omb);
        else lp.setMargins(mc.ml, mc.mt, mc.mr, mc.mb);
        this.setLayoutParams(lp);
    }
    else if (p instanceof RelativeLayout.LayoutParams) {
        RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams)p;
        if (_default) lp.setMargins(mc.oml, mc.omt, mc.omr, mc.omb);
        else lp.setMargins(mc.ml, mc.mt, mc.mr, mc.mb);
        this.setLayoutParams(lp);
    }
    else if (p instanceof TableRow.LayoutParams) {
        TableRow.LayoutParams lp = (TableRow.LayoutParams)p;
        if (_default) lp.setMargins(mc.oml, mc.omt, mc.omr, mc.omb);
        else lp.setMargins(mc.ml, mc.mt, mc.mr, mc.mb);
        this.setLayoutParams(lp);
    }
}

Because this.getLayoutParams();returns a ViewGroup.LayoutParams, which do not have the attributes topMargin, bottomMargin, leftMargin, rightMargin. The mc instance you see is just a MarginContainer which contains offset (-3dp) margins and (oml, omr, omt, omb) and the original margins (ml, mr, mt, mb).




Here is the all-in-one answer with recent updates:

Step 1, to update margin

The basic idea is to get margin out and then update it. The update will be applies automatically and you do not need to set it back. To get the layout parameters, simply call this method:

LayoutParams layoutParams = (LayoutParams) yourView.findViewById(R.id.THE_ID).getLayoutParams();

The LayoutParams comes from the layout of your view. If the view is from a linear layout, you need to import LinearLayout.LayoutParams. If you use relative layout, import LinearLayout.LayoutParams , etc.

Now, if you set the margin using Layout_marginLeft, Right, etc, you need to update margin in this way

layoutParams.setMargins(left, top, right, bottom);

If you set margin using the new layout_marginStart, you need to update margin in this way

layoutParams.setMarginStart(start);
layoutParams.setMarginEnd(end);

Step 2, to update margin in dp

All two ways of updating margin above are updating in pixels. You need to do a translation of dp to pixels.

float dpRatio = context.getResources().getDisplayMetrics().density;
int pixelForDp = (int)dpValue * dpRatio;

Now put the calculated value to the above margin update functions and you should be all set




int sizeInDP = 16;

int marginInDp = (int) TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_DIP, sizeInDP, getResources()
                    .getDisplayMetrics());

Then

layoutParams = myView.getLayoutParams()
layoutParams.setMargins(marginInDp, marginInDp, marginInDp, marginInDp);
myView.setLayoutParams(layoutParams);

Or

LayoutParams layoutParams = new LayoutParams...
layoutParams.setMargins(marginInDp, marginInDp, marginInDp, marginInDp);
myView.setLayoutParams(layoutParams);



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