onAttachedToWindow调用

修改窗口的尺寸要在onAttachedToWindow后才能成功，在这之前，getWindow().getDecorView().getLayoutParams返回值是空的

DecorView的LayoutParams是在ActivityThread.handleResumeActivity中调用WindowManagerGlobal.addView进行设置的，

root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
// do this last because it fires off messages to start doing things
try {
    root.setView(view, wparams, panelParentView); 
} catch (RuntimeException e) {
    // BadTokenException or InvalidDisplayException, clean up.
    if (index >= 0) {
        removeViewLocked(index, true);
    }
    throw e;
}

在这之后会在ViewRootImpl.setView中通过requestLayout触发performTraversals 最终回调到Activity.onAttachedToWindow

private void performTraversals() {
    // cache mView since it is used so much below...
    final View host = mView;
    ...
    host.dispatchAttachedToWindow(mAttachInfo, 0);
    ...
}

调用流程
View.dispatchAttachedToWindow-->DecorView.onAttachedToWindow-->Activity.onAttachedToWindow