Flutter 部分安卓手机 Android12 软键盘无法正常

遇到一个很奇怪的问题，flutter在自己的手机上，textfield可以正常获取焦点，但是软键盘无法正常弹出。手机型号是realMe ,系统是12。试了其他的品牌的手机，均可以正常弹出软键盘。
异常日志：W/InputMethodManager: Ignoring showSoftInput() as view=io.flutter.embedding.android.FlutterView is not served.

最终解决方案

在Flutter Android工程包的MainActivity增加如下代码

@Override
    protected void onResume() {
        super.onResume();
        FlutterView flutterView = findViewById(FLUTTER_VIEW_ID);
        flutterView.requestFocus();
    }

其他

Flutter软键盘异常的问题很多，我的解决方案只是针对我遇到的报错，有些其他的原因，也会导致软键盘异常。比如未开启硬件加速，或者webview软键盘不弹出，都是其他的解决方案。

问题排查回顾

首先看了打印的异常日志：

W/InputMethodManager: Ignoring showSoftInput() 
as view=io.flutter.embedding.android.FlutterView
 is not served.

从日志来看，貌似显示软键盘的方法没有执行成功。
于是进入InputMethodManager查看源码：

 if (!hasServedByInputMethodLocked(view)) {
                Log.w(TAG, "Ignoring showSoftInput() as view=" + view + " is not served.");
                return false;
            }

/**
     * Returns {@code true} when the given view has been served by Input Method.
     */
    private boolean hasServedByInputMethodLocked(View view) {
        final View servedView = getServedViewLocked();
        return (servedView == view
                || (servedView != null && servedView.checkInputConnectionProxy(view)));
    }

结合源码我推测，显示软键盘没有成功送达到FlutterView。我估计问题出在FlutterView，也许FlutterView 失焦了。
那么FlutterView 是什么呢？这边我就不赘述了，感兴趣的可以自己搜索一下。
首先得获取到FlutterView,
进入FlutterActivitya源码

/**
   * The ID of the {@code FlutterView} created by this activity.
   *
   * <p>This ID can be used to lookup {@code FlutterView} in the Android view hierarchy. For more,
   * see {@link android.view.View#findViewById}.
   */
  public static final int FLUTTER_VIEW_ID = ViewUtils.generateViewId(0xF1F2);

可以通过FLUTTER_VIEW_ID获取FlutterView

@Override
    protected void onResume() {
        super.onResume();
        FlutterView flutterView = findViewById(FLUTTER_VIEW_ID);
        flutterView.requestFocus();
    }

于是我就在想通过，主动给FlutterView 设置焦点，尝试之后，软键盘正常了。