Android 11 toast居中显示

        Android 11以后，系统Toast的text toast被设置为固定在屏幕下方显示，通过setGravity已经不会生效。

        为了解决这个问题，去看了Toast源码。从show()方法开始，

        

    /**
     * Show the view for the specified duration.
     */
    public void show() {
        if (Compatibility.isChangeEnabled(CHANGE_TEXT_TOASTS_IN_THE_SYSTEM)) {
            checkState(mNextView != null || mText != null, "You must either set a text or a view");
        } else {
            if (mNextView == null) {
                throw new RuntimeException("setView must have been called");
            }
        }

        INotificationManager service = getService();
        String pkg = mContext.getOpPackageName();
        TN tn = mTN;
        tn.mNextView = mNextView;
        final int displayId = mContext.getDisplayId();

        try {
            if (Compatibility.isChangeEnabled(CHANGE_TEXT_TOASTS_IN_THE_SYSTEM)) {
                if (mNextView != null) {
                    // It's a custom toast
                    service.enqueueToast(pkg, mToken, tn, mDuration, displayId);
                } else {
                    // It's a text toast
                    ITransientNotificationCallback callback =
                            new CallbackBinder(mCallbacks, mHandler);
                    service.enqueueTextToast(pkg, mToken, mText, mDuration, displayId, callback);
                }
            } else {
                service.enqueueToast(pkg, mToken, tn, mDuration, displayId);
            }
        } catch (RemoteException e) {
            // Empty
        }
    }

到TN的handleShow()方法，

        public void handleShow(IBinder windowToken) {
            if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView
                    + " mNextView=" + mNextView);
            // If a cancel/hide is pending - no need to show - at this point
            // the window token is already invalid and no need to do any work.
            if (mHandler.hasMessages(CANCEL) || mHandler.hasMessages(HIDE)) {
                return;
            }
            if (mView != mNextView) {
                // remove the old view if necessary
                handleHide();
                mView = mNextView;
                mPresenter.show(mView, mToken, windowToken, mDuration, mGravity, mX, mY,
                        mHorizontalMar