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Mario López Batres
Asked: 2020-01-21 12:57:58 +0800 CST 2020-01-21 12:57:58 +0800 CST

Work with dp on Android

  • 772

I think my question should be simple to answer, but I really don't know the answer so here goes:

I am trying to subtract the original height from a layout50 dps. Right now I do it as follows:

v.getLayoutParams().height = initialHeight -  50;
v.requestLayout();

The problem with this is that it's subtracting via the metric px, and I'd like to work withdp

java

5 Answers

  1. Best Answer

    You can convert from dp to pixels as follows:

    // tu cálculo del valor en dp
final float alturaDp = initialHeight - 50;

// Obtener la densidad de pantalla
final float escala = getResources().getDisplayMetrics().density;
// Convertir los dps a pixels, basado en la escala de densidad
alturaPx = (int) (alturaDp * escala + 0.5f);

    Original source in the official documentation available in Spanish.

    Since the answer so far didn't seem helpful, just so you understand:

    Can't work with dp in LayoutParams. Internally, the classes work with pixels. So the only way to work with values ​​in dp is to convert them to pixels and then apply the pixels.

    • 17

  2. Another alternative is to define the dp unit in the dimens.xml file

    <dimen name="resta_height">50dp</dimen>

    and in your code put:

    v.getLayoutParams().height = initialHeight - (int)getResources().getDimension(R.dimen.resta_height);

    font

    • 4

  3. The correct way is described in the Android source code :

    final float scale = getContext().getResources().getDisplayMetrics().density;
int pixels = (int) (dps * scale + 0.5f);

    by Romain Guy who was working with Android at its inception.

    This is also described in the documentation: Converting dp units to pixel units.

    // El umbral gestual expresado en dp
private static final float GESTURE_THRESHOLD_DP = 16.0f;

//Obtener la escala de densidad de la pantalla.
final float scale = getResources().getDisplayMetrics().density;
// Convertir el dps en píxeles, basado en la escala de densidad
mGestureThreshold = (int) (GESTURE_THRESHOLD_DP * scale + 0.5f);

// Usar mGestureThreshold como una distancia en píxeles...

    Method to convert dp to pixels.

    public int getPixelsfromDP(Context ctx, float dps) {
      float scale = ctx.getResources().getDisplayMetrics().density;
      return (int) (dps * scale + 0.5f);
}
    • 3

  4. You should convert the 50dp you want to pixels and then subtract these pixels from the height of the view. The number of pixels will be different depending on the pixel density of the device.

    Resources r = getResources();
float pixels = TypedValue.applyDimension(
    TypedValue.COMPLEX_UNIT_DIP, 50, r.getDisplayMetrics());

v.getLayoutParams().height = initialHeight - pixels;
v.requestLayout();
    • 1

  5. This can help you, it explains very well how dp works, it helped me a lot:

    What are DPs in Android and what are they for?

    • 0