getWidth and getHeight are returning a zero

Question

I am trying to make a simple drawing program for the android.

I have a custom View class to handle the drawing. When I call its getWidth and getHeight metheds, I get a zero.

But, the drawing works fine, I hard code in the width and height so it works. Why is it doing this?

My View class

public class cDrawing extends View{

    char BitMap[];
    static final short WIDTH=160;
    static final short HEIGHT=440;
    static final char EMPTY=' ';
    int mWidthSize;
    int mHeightSize;

    static final char RED ='R';
    int y;

    public cDrawing(Context context) {
        super(context);

        y=3;
        // set up our bitmap
        BitMap=new char[WIDTH*HEIGHT];
        for(int i=0; i<WIDTH*HEIGHT; i++)
                BitMap[i]=EMPTY;


        // returns zero why???????
        int h=getHeight();
        h=400;
        int w=getWidth();
        w=320;
        mWidthSize=w/WIDTH;
        mHeightSize=h/HEIGHT;


        // TODO Auto-generated constructor stub
    }

The Activity class

public class cCanves extends Activity  implements OnClickListener {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.canves);
        cDrawing board=new cDrawing(this);


        LinearLayout layout = (LinearLayout)findViewById(R.id.parent2);
        layout.addView(board);


        // set up buttons
        View mEraser = findViewById(R.id.buteraser);
        mEraser.setOnClickListener(this);

        View mBlack = findViewById(R.id.butblack);
        mBlack.setOnClickListener(this);

        View mWhite = findViewById(R.id.butwhite);
        mWhite.setOnClickListener(this);

        View mRed = findViewById(R.id.butred);
        mRed.setOnClickListener(this);

    } // end function

    public void onClick(View v) {
        Intent i;
        switch(v.getId())
        {
        case R.id.buteraser:
            break;
        case R.id.butblack:
            break;
        case R.id.butwhite:
            break;
        case R.id.butred:
            break;
        } // end switch

    }   // function
}

the xml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="@+id/parent"
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:orientation="vertical"
  android:layout_height="fill_parent">

    <LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="wrap_content"
      android:orientation="horizontal"
      android:layout_height="wrap_content">

    <ImageButton android:id="@+id/buteraser"
      android:src="@drawable/icon"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>

    <ImageButton android:id="@+id/butblack"
      android:src="@drawable/icon"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>

    <ImageButton android:id="@+id/butwhite"
      android:src="@drawable/icon"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>

    <ImageButton android:id="@+id/butred"
      android:src="@drawable/icon"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>
    </LinearLayout>

    <LinearLayout android:id="@+id/parent2"
      android:layout_width="fill_parent"
      android:orientation="vertical"
      android:layout_height="fill_parent">
    </LinearLayout>


</LinearLayout>

You have to wait until your view has been instantiated and given its dimensions. Everything should be ready by the onDraw function. — Robert Massaioli
– Robert Massaioli, Commented May 27, 2011 at 5:52
possible duplicate of How do you to retrieve dimensions of a view? Getheight() and Getwidth() always return zero — senderle
– senderle, Commented Jul 26, 2012 at 10:01

mah · Accepted Answer · 2015-07-27 13:16:14Z

19

The width and height are not defined until the view is actually rendered to the screen.

Use protected abstract void onLayout (boolean changed, int l, int t, int r, int b) (which you override in your activity) to know when the sizes are ready.

edited Jul 27, 2015 at 13:16

answered May 26, 2011 at 21:10

mah

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2 Comments

Ted pottel Over a year ago

Thank you,i have another program where thius works fine, i'll see if I'm doing it after the view iks displayed

Muhammad Kashif Nazar Over a year ago

As answered by Ginsan below, onLayout is the best place to call the getHeight and getWidth methods.

JJD · Accepted Answer · 2015-04-13 14:22:14Z

6

Complementing Mah's answer, I found out that you can get the values from parameters, like the code bellow:

ImageView imageProcess = (ImageView) li.inflate(
    R.layout.andamento_sinistro_imageprocess, centerLayout, false);
imageProcess.setBackgroundResource(
    (isActive)?(R.drawable.shape_processon):(R.drawable.shape_processoff));
RelativeLayout.LayoutParams imageProcessParams = 
    (RelativeLayout.LayoutParams)imageProcess.getLayoutParams();
imageProcessParams.leftMargin = 
    (int) (centerPosition - 0.5*imageProcessParams.width);
imageProcessParams.addRule(RelativeLayout.CENTER_VERTICAL);
centerLayout.addView(imageProcess);

The real catch here is the use of the LayoutParams, that have rules yet not processed by the element.

edited Apr 13, 2015 at 14:22

JJD

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answered Dec 1, 2011 at 15:49

Luiz Vianna

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Comments

Jack Smartie · Accepted Answer · 2011-05-26 21:06:45Z

3

I'm not certain, but it may have something to do with where the code is in the lifecycle of your activity. If you're calling getWidth() and getHeight() before the View is displayed on screen, you'll get a value of 0. I've had that happen to me, too.

I'm not sure if there's a way around this. I had to rely on getting the hardware screen's width and height, instead of the view's width and height. You might end up having to approximate the width and height of your view and hard coding it.

answered May 26, 2011 at 21:06

Jack Smartie

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1 Comment

Alex Lockwood Over a year ago

The drawing of the layout onto the screen is not directly related to the Activity lifecycle.

Ginsan · Accepted Answer · 2013-12-02 13:56:49Z

1

You should call getWidth() and getHeight() in the overrided method onLayout.

answered Dec 2, 2013 at 13:56

Ginsan

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1 Comment

Muhammad Kashif Nazar Over a year ago

This is the exactly what should have been the correct answer.

KRIPA SHANKAR JHA · Accepted Answer · 2018-08-01 07:21:37Z

0

Just Use the getViewTreeObserver() Listener, and inside this just calculate the height and width.

Follow the code :

getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { //Do your Stuff calculation , like view.getWidth() ... });

answered Aug 1, 2018 at 7:21

KRIPA SHANKAR JHA

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Comments

vieux · Accepted Answer · 2011-05-26 21:06:49Z

-6

The view only has dimensions after beeing displayed for the first time.

Other thing:

int h=getHeight();
h=400;

Is useless no ? Is it just for testing ?

answered May 26, 2011 at 21:06

vieux

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