android中View的GONE和INVISIBLE的原理

標籤：

廢話只重複兩句；

GONE真的隱藏；

INVISIBLE不可見但是預留了View的位置；

網上千篇一律的重複著這兩句話並舉著例子，並沒有觀察本質來作區分。查看源碼後得知其區別希望廣大朋友能夠借鑒，源碼如下：

 /* Check if the GONE bit has changed */        if ((changed & GONE) != 0) {            needGlobalAttributesUpdate(false);            requestLayout();            if (((mViewFlags & VISIBILITY_MASK) == GONE)) {                if (hasFocus()) clearFocus();                clearAccessibilityFocus();                destroyDrawingCache();                if (mParent instanceof View) {                    // GONE views noop invalidation, so invalidate the parent                    ((View) mParent).invalidate(true);                }                // Mark the view drawn to ensure that it gets invalidated properly the next                // time it is visible and gets invalidated                mPrivateFlags |= PFLAG_DRAWN;            }            if (mAttachInfo != null) {                mAttachInfo.mViewVisibilityChanged = true;            }        }        /* Check if the VISIBLE bit has changed */        if ((changed & INVISIBLE) != 0) {            needGlobalAttributesUpdate(false);            /*             * If this view is becoming invisible, set the DRAWN flag so that             * the next invalidate() will not be skipped.             */            mPrivateFlags |= PFLAG_DRAWN;            if (((mViewFlags & VISIBILITY_MASK) == INVISIBLE)) {                // root view becoming invisible shouldn‘t clear focus and accessibility focus                if (getRootView() != this) {                    if (hasFocus()) clearFocus();                    clearAccessibilityFocus();                }            }            if (mAttachInfo != null) {                mAttachInfo.mViewVisibilityChanged = true;            }        }

 

如果在GONE和INVISIBLE兩者都可以完成你的效果，那麼你應該選擇INVISIBLE。因為從源碼中來看GONE需要重新的布局和通知上級View去重新整理，有緩衝還要清空緩衝；從視圖變更開銷的來說INVISIBLE要更加的划算一些，如果你的View不是十分佔用資源的情況！！！也非常歡迎大家說出自己的看法。

android中View的GONE和INVISIBLE的原理