NullPointerException在ViewGroup.java:3528中调用removeFromArray

Question

请帮助解决这个奇怪的问题：

source code:

if(view != null && view.getParent() != null) {
    ((ViewGroup)view.getParent()).removeView(view);
}

---

如你所见，view和view.getParent（）不能为null调用removeView， 但这是我们得到的例外：

---

java.lang.NullPointerException
    at android.view.ViewGroup.removeFromArray(ViewGroup.java:3528)
    at android.view.ViewGroup.removeViewInternal(ViewGroup.java:3726)
    at android.view.ViewGroup.removeViewInternal(ViewGroup.java:3690)
    at android.view.ViewGroup.removeView(ViewGroup.java:3622)
    at xxxx.removeView(yyyy.java:zzzz) // here's code above

---

，这是ViewGroup.java中的相关代码：

private void removeFromArray(int index) {
    final View[] children = mChildren;
    if (!(mTransitioningViews != null && mTransitioningViews.contains(children[index]))) {
        children[index].mParent = null;  // !!!! ViewGroup.java:3528
    }

index对应一个子视图，所以子[index]应该是我们代码中的“view”，而mParent应该是“view.getParent（）”，那么为什么这里抛出一个NullPointerException？

---

整体代码：

if(view != null && view.getParent() != null) {
    ((ViewGroup)view.getParent()).removeView(view);
}

public void removeView(View view) {
    removeViewInternal(view);
}

private void removeViewInternal(View view) {
    final int index = indexOfChild(view);
    if (index >= 0) {
        removeViewInternal(index, view);
    }
}

public int indexOfChild(View child) {
    final int count = mChildrenCount;
    final View[] children = mChildren;
    for (int i = 0; i < count; i++) {
        if (children[i] == child) {
            return i;
        }
    }
    return -1;
}

private void removeViewInternal(int index, View view) {
    ......
    removeFromArray(index);
}

private void removeFromArray(int index) {
    final View[] children = mChildren;
    if (!(mTransitioningViews != null && mTransitioningViews.contains(children[index]))) {
        children[index].mParent = null;  // !!!! ViewGroup.java:3528
    }

Answer 1

您没有对View []子项进行空检查。在Array of Object类型中，默认情况下，每个索引位置都使用空值初始化。

View[] children = new View[10]; //Here Array is not null. but all elements inside it are null

for(int i=0;i<children.length;i++){
    System.out.println(children[i] == null); //certainly true
}

//proper initialization
for(int i=0;i<children.length;i++){
    children[i] = new View();
}