How to position the view with margin that will look same for all devices?

问题

I'm trying to position a view in the center to make it look good by adding 130 (margin-top) programmatically, however, I'm not sure how to give other android devices such as tablets to look the same? adding 130 to the margin-top looks good on the normal android phone but will look different on a tablet. How will I able to make a logic to give a margin-top that will provide the same look on all devices? Some examples or tip would be great! I would love to hear from you!

margin_top = 130 // How to make this look good on all devices? 

ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) v.getLayoutParams();
p.setMargins(0, margin_top, 0, 0);
v.requestLayout();

回答1:

My approach to this is the following:

1). Get the device height. Also check this answer.

DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int height = displayMetrics.heightPixels;

2). Calculate the ratio.

You have set a top margin of 130dp I assume. Using pixplicity I managed to convert it to px.

Your phone has a resolution height x weight in pixels. Let's define height as phoneHeight.

Here it becomes a little tricky for me too. As you can see 130dp has different pixel values for ldpi, mdpi, etc. I personally don't know which one you should use, you might try the mdpi one. (I'll try to research more and come back with an answer).

LE:

You can use this method to convert dp to pixels according to your phone. (See this answer).

public static float convertDpToPixel(float dp, Context context){
    Resources resources = context.getResources();
    DisplayMetrics metrics = resources.getDisplayMetrics();
    float px = dp * ((float)metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT);
    return px;
}

Use the returned px into the formula below. (let's call the returned px - convertedPx.

3). The formula for the top margin's value.

If we use the value of 130dp for mdpi from the table we get 130px. So the formula would be:

margin_top = (convertedPx / phoneHeight) * height

with phoneHeight the height of the phone you are currently testing on and height the height of the device using displayMetrics.

NOTICE: convertedPx will be a constant. You only have to run this method (convertDpToPixel) on your phone to find out how much 130dp mean in pixels.

来源：https://stackoverflow.com/questions/51710777/how-to-position-the-view-with-margin-that-will-look-same-for-all-devices