从创建AlertDialog发生crash的WindowManager$BadTokenException看Window和Surface_如何通过service创建dialog badtokenexception-优快云博客

本文链接：https://blog.youkuaiyun.com/aaajj/article/details/129338883

在AndroidService中直接调用AlertDialog可能会导致WindowManager$BadTokenException，因为Service没有Activity的上下文。通过设置dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY)可以解决问题，但这需要相应的权限。文章解释了WindowManager、ViewRootImpl在绘制机制中的角色，并提供了异常的原因和解决方案。

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在service中，进行AlertDialog调用，如

void showDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.Theme_MyApplication);
        builder.setTitle("Test");
        builder.setMessage("hello, ");
        builder.setNegativeButton("cancel1", new DialogInterface.OnClickListener() {
@Override
            public void onClick(DialogInterface dialogInterface, int i) {
                dialogInterface.dismiss();
            }
        });
        AlertDialog dialog = builder.create();
//加上这个setType和赋权悬浮窗口后，就没有问题了，这里注释掉，展现出问题
//        dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY);
        dialog.show();
    }

会导致crash，

     Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
        at android.view.ViewRootImpl.setView(ViewRootImpl.java:1312)
        at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:405)
        at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
        at android.app.Dialog.show(Dialog.java:352)
        at com.example.myapplication.MyService.showDialog(MyService.java:28)
        at com.example.myapplication.MyService.onStartCommand(MyService.java:40)
        at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:4655)
        at android.app.ActivityThread.-$$Nest$mhandleServiceArgs(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2180) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loopOnce(Looper.java:201) 
        at android.os.Looper.loop(Looper.java:288) 
        at android.app.ActivityThread.main(ActivityThread.java:7872) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)

这个问题，只有设置了TYPE_APPLICATION_OVERLAY 就可以了，因为ViewRootImpl.setView里会判断type的值，对于不符合条件的，就抛出了异常。

dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY);

这里重点关注这个堆栈

at android.view.ViewRootImpl.setView(ViewRootImpl.java:1312)

at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:405)

at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)

WindowManager的addView调用到ViewRootImpl的setView

就这个调用，可以作为一个入口来理解绘图机制，WindowManager在这个过程中创建了Surface，WindowManager作为窗口的管理者出现在这里，其他的绘图处理就交给ViewRootImpl和SurfaceFlinger合成了，详细可参考

https://blog.youkuaiyun.com/yangwen123/article/details/80674965?spm=1001.2014.3001.5502