View's getWidth() and getHeight() returning 0

问题:

I have looked at the similar questions and tried their solutions but it did not work for me. I try to take width of an imageView, but it returns 0. Here is the code:

public class MainActivity extends Activity {
private ImageView image1;   
float centerX,centerY;
private ImageView image2;
private boolean isFirstImage = true;

@Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.rotate);
    image1 = (ImageView) findViewById(R.id.ImageView01);
    image2 = (ImageView) findViewById(R.id.ImageView02);
    image2.setVisibility(View.GONE);

    if (isFirstImage) {
        applyRotation(0, 90);
        isFirstImage = !isFirstImage;
    }   
}   

private void applyRotation(float start, float end) {


            centerX=image1.getWidth()/2.0f;
    centerY=image1.getHeight()/2.0f;
    final Flip3dAnimation rotation =

    new Flip3dAnimation(start, end,centerX , centerY);
    rotation.setDuration(500);
    rotation.setFillAfter(true);
    rotation.setInterpolator(new AccelerateInterpolator());
    rotation.setAnimationListener(new DisplayNextView(isFirstImage, image1,
            image2));

    if (isFirstImage)
    {
        image1.startAnimation(rotation);
    } else {
        image2.startAnimation(rotation);
    }
}
}

Can anyone help me with this? Thanks

回答1:

You need to use the onSizechanged() method.

This is called during layout when the size of this view has changed

回答2:

You are either accessing the ImageViews width and height before it has been measured, or after you set its visibility to GONE.

image2.setVisibility(View.GONE);

Then getWidth() or getHeight() will return 0.,

You can also have a look at onWindowFocusChanged(), onSizeChanged() and onMeasure():

 @Override
 public void onWindowFocusChanged(boolean focus) {
    super.onWindowFocusChanged(focus);
    // get the imageviews width and height here
 }

回答3:

You should use: image1.getLayoutParams().width;

回答4:

public class GETImageView extends ImageView {

public GETImageView (Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    Drawable d = getDrawable();

    if (d != null) {
        int width = MeasureSpec.getSize(widthMeasureSpec);
    }
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}

The ImageView have not yet draw the image, so no width or height return. You may use a subclass to get the imageview width.

Here is some link provide you another easy methods:

How to get the width and height of an android.widget.ImageView?

How to get the width and height of an Image View in android?

Android ImageView return getWidth, getHeight zero

Hope this help you.

回答5:

you can use OnGlobalLayoutListener for the ImageView image1 so you can get exact width and height occupied by the view in the layout...as

image1 = (ImageView) findViewById(R.id.ImageView01);
        ViewTreeObserver viewTreeObserver = image1.getViewTreeObserver();
        viewTreeObserver
                .addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
                    @Override
                    public void onGlobalLayout() {
                        if (isFirstImage) {
                            applyRotation(0, 90);
                            isFirstImage = !isFirstImage;
                        } 
                        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN)
                            image1.getViewTreeObserver()
                                    .removeOnGlobalLayoutListener(this);
                        else
                            image1.getViewTreeObserver()
                                    .removeGlobalOnLayoutListener(this);
                    }
                });

回答6:

By the way, views don't get sized until the measurement steps have been taken. See this link:

getWidth() and getHeight() of View returns 0

回答7:

Maybe you should call View.measure(int,int) first.
Since the width and height is not defined until this view is draw. You can call measure by hand to enforce this view to calculate it's size;

回答8:

Please using a Handler and get height and width on this with delay time >= 10

This may be useful for use:

@Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        getHeight();

    }

    private void getHeight() {
        // TODO Auto-generated method stub
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(getApplicationContext(), "Height:" + mAnimationView.getMeasuredHeight(),
                        Toast.LENGTH_SHORT).show();
            }
        }, 10L);

    }