How to calculate dp from pixels in android programmatically

Question

I want to calculate dp from px programmatically. How to do it? I get resolution from:

DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
ht = displaymetrics.heightPixels;
wt = displaymetrics.widthPixels;

Solution 1

All the answers here show a dp->px conversion rather than px->dp, which is what the OP asked for. Note that TypedValue.applyDimension cannot be used to convert px->dp, for that you must use the method described here: https://stackoverflow.com/a/17880012/504611 (quoted below for convenience).

fun Context.dpToPx(dp: Int): Int {
    return (dp * resources.displayMetrics.density).toInt()
}

fun Context.pxToDp(px: Int): Int {
    return (px / resources.displayMetrics.density).toInt()
}

Solution 2

float ht_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, ht, getResources().getDisplayMetrics());
float wt_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, wt, getResources().getDisplayMetrics());

Solution 3

This should give you the conversion pixels -> dp:

DisplayMetrics displaymetrics = new DisplayMetrics();
int dp = (int) TypedValue.applyDimension( TypedValue.COMPLEX_UNIT_DIP, myPixels, displaymetrics );

Solution 4

DisplayMetrics dm = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        String str_ScreenSize = "The Android Screen is: "
                    + dm.widthPixels
                    + " x "
                    + dm.heightPixels;

        TextView mScreenSize = (TextView) findViewById(R.id.strScreenSize);
        mScreenSize.setText(str_ScreenSize);

can u cheeck it out..

or this may also help u

int value = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 
                     (float) 123.4, getResources().getDisplayMetrics());

View more solutions

Comments

[Palani]

Question is about "px -> dp" , but the code looks like "dp -> px" ?? (note the '_px' suffix in LHS )

[Vicky Chijwani]

What you're doing is a dp->px conversion. The docs for TypedValue.applyDimension say that the first argument is the unit to convert from, and the return value is the "complex floating point value multiplied by the appropriate metrics depending on its unit." applyDimension cannot be used to convert px->dp, for that you must do it as described here: stackoverflow.com/a/17880012/504611

[Jerry Destremps]

This is converting the opposite way from question.

[Goldorak84]

This should be the accepted answer

[user3290180]

it's definitely the best answer I found about this problem. It's usable in every class.

[DeltaCap019]

any way you can change first parameter to TypedValue.COMPLEX_UNIT_PX from TypedValue.COMPLEX_UNIT_DIP so as to convert dp-> px

[android developer]

This is the correct answer: return px / (context.getResources().getDisplayMetrics().densityDpi / 160f)

[Naveed Ahmad]

perfect answer Thanks

[Vicky Chijwani]

@NullnVoid: That won't work. If you see the docs for TypedValue.applyDimension, it says: "Converts an unpacked complex data value holding a dimension to its final floating point value", i.e., the return value is always in px. So if you pass TypedValue.COMPLEX_UNIT_PX it will just do a px->px "conversion", which is to say, nothing.

[Farshad Tahmasbi]

funny! Although it is not the real answer but it's still useful

[kike]

Use toInt() method instead of casting for Kotlin.

[Ayaz Alifov]

@androiddeveloper, please explain why you think using densityDpi is better than density.

[android developer]

@SaQada Look at the docs: developer.android.com/reference/android/util/… : "The logical density of the display", "This value does not exactly follow the real screen size" , "To obtain the current density for a specific display, use densityDpi" . However, now that I've tested both ways, both seem to work fine. Just try to prefer float or double instead of int, because int might lose some precision on some cases. For example, try to convert the height to dp and back to px on QVGA, and you will get 319 instead of 320.

[Ahamadullah Saikat]

The best solution ever.

[EpicPandaForce]

Resource.getSystem() has no guarantee when multiple Displays exist.