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【Android】getwidth和getmeasuredwidth的区别以及两者的使用场景

2018年09月25日 移动开发 ⁄ 共 1512字 ⁄ 字号 评论关闭

首先,看getWidth()的官方说明:

public final int getWidth ()

Added in API level 1

Return the width of the your view.

Returns
  • The width of your view, in pixels.

返回view的宽度,说的不详细,再看getWidth源码:

<span style="font-size:18px;">    /**
     * Return the width of the your view.
     *
     * @return The width of your view, in pixels.
     */
    @ViewDebug.ExportedProperty(category = "layout")
    public final int getWidth() {
        return mRight - mLeft;
    }</span>

从源码可以看出,getwidth返回的是右边坐标减轻坐标减去左边坐标,这要在布局之后才能确定它们的坐标,也就是说在布局后才能调用getwidth来获取。所以getWidth()获得的宽度是View在设定好布局后整个View的宽度。


而对于getmeasuredwidth,

public final int getMeasuredWidthAndState ()

Added in API level 11

Return the full width measurement information for this view as computed by the most recent call to measure(int,
int)
. This result is a bit mask as defined byMEASURED_SIZE_MASK and MEASURED_STATE_TOO_SMALL.
This should be used during measurement and layout calculations only. Use getWidth() to
see how wide a view is after layout.

Returns
  • The measured width of this view as a bit mask.

得到的是最近一次调用measure()方法测量后得到的是View的宽度,它应该仅仅用在测量和Layout的计算中。再看源码:

    /**
     * Like {@link #getMeasuredWidthAndState()}, but only returns the
     * raw width component (that is the result is masked by
     * {@link #MEASURED_SIZE_MASK}).
     *
     * @return The raw measured width of this view.
     */
    public final int getMeasuredWidth() {
        return mMeasuredWidth & MEASURED_SIZE_MASK;
    }

return The raw measured width of this view 获得的是原始的测量宽度。所以说getMeasuredWidth()是对View上的内容进行测量后得到的View内容占据的宽度。前提是你必须在父布局的onLayout()方法或者此View的onDraw()方法里调用measure(0,0);(measure中的参数的值你自己可以定义),否则你得到的结果和getWidth()得到的结果是一样的。


两者的使用场合:

getMeasuredWidth:在自定义view重写onLayout时、在我们用layoutinflater动态加载view后想获得view的原始宽度时。

getWidth:一般在view已经布局后呈现出来了,想获取宽度时


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