What triggers a View's measure() to be called

Question

In my application I have an infinite loop on one of my View\'s onMeasure() overrides. Debugging the source code starting from a break point in my onMeasure, I am able to trace

Answer 1

In order to trigger a measure pass for a custom View you must call the requestLayout() method. For example, if you are implementing a custom view that extends View and it will behave like a TextView, you could write a setText method like this:

/**
 * Sets the string value of the view.
 * @param text the string to write
 */
public void setText(String text) {
    this.text = text;

            //calculates the new text width
    textWidth = mTextPaint.measureText(text);

    //force re-calculating the layout dimension and the redraw of the view
    requestLayout();
    invalidate();
}

Answer 2

Well, If you are changing a View's content, it will eventually have to call invalidate(). For example, you have a TextView with a text called "Text 1". Now, you change the text of the same TextView to "Text 2". Here aslo, invalidate will be called.

So basically, when something changes on the view, more often than not, you would expect the invalidate method to be called, and a corresponding call to the measure().

Look at the source code for TextView, for example. http://www.google.com/codesearch#uX1GffpyOZk/core/java/android/widget/TextView.java&q=TextView%20package:android&type=cs

Count the number of invalidate calls. There are quite a few.