Android Dialog.show返回badtoken错误的代码

我建立了一个预算跟踪系统来跟踪我的开支

我在应用程序的某些部分有一个对话框弹出选项，在我升级android studio之前，这些都可以正常工作

现在我在dialog.show代码运行时遇到了一个错误，它与窗口的实例化方式有关，有人能帮忙吗

下面是代码片段

   private void checkforexbase() throws IOException {
    String pathcat=Environment.getExternalStorageDirectory()+"/"+appfolder+"/";
    File file=new File(pathcat+"forex.txt");
if(file.exists())Toast.makeText(ctx,"Base set",Toast.LENGTH_LONG).show();
    else {
Locale loc = Locale.getDefault();
Currency currency = Currency.getInstance(loc);
final String currentcurr=currency.getCurrencyCode().toString();
WindowManager windowManager;
int layoutParams=WindowManager.LayoutParams.TYPE_TOAST;

final Dialog forexch =new Dialog(ctx);//-> dialog initiated

View view= View.inflate(ctx,R.layout.forxchoose,null);
view.inflate(ctx,R.layout.forxchoose,null);
forexch.getWindow().setBackgroundDrawable(new ColorDrawable(android.graphics.Color.TRANSPARENT));
//forexch.getWindow().setType(Window.FEATURE_CONTENT_TRANSITIONS);
forexch.getWindow().setLayout(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT);
TextView currtex=(TextView) view.findViewById(R.id.currencytex);
forexch.setContentView(view);
 final Spinner spinner = (Spinner) view.findViewById(R.id.forexsp);
final ArrayAdapter<CharSequence> adapter = 
ArrayAdapter.createFromResource(ctx,
        R.array.forexlis, android.R.layout.simple_spinner_item);
spinner.setOnItemSelectedListener(new 
AdapterView.OnItemSelectedListener() {
     public void onItemSelected(AdapterView<?> adapterView, View view, 
int i, long l) {
if(forxspinfirstrun==true)forexch.dismiss();
        else forxspinfirstrun=true;
        String array[]     = getResources().getStringArray(R.array.forexlis);
        basecurr=array[i].toString();
        forcurr=basecurr;
        try {
            writecurrencybase();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        //Toast.makeText(ctx, array[i].toString(),Toast.LENGTH_LONG ).show();
        }
    public void onNothingSelected(AdapterView<?> adapterView) {
        forxspinfirstrun=false;
        //Toast.makeText(ctx,"Select a currency",Toast.LENGTH_LONG).show();
        return;
    }
});
currtex.setText(currentcurr);
final Button buttonok=(Button)view.findViewById(R.id.buttonokforx);
final Button buttonchange=(Button)view.findViewById(R.id.buttonchangeforx);
  buttonok.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        basecurr=currentcurr;
      //Toast.makeText(ctx,"Base currency set",Toast.LENGTH_LONG).show();
        forexch.dismiss();
        try {
            writecurrencybase();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


});
buttonchange.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
buttonok.setVisibility(View.INVISIBLE);
        buttonchange.setOnClickListener(null);
        spinner.setVisibility(View.VISIBLE);adapter.setDropDownViewResource(android.R.layout.select_dialog_multichoice);
          adapter.setDropDownViewResource(R.layout.forexspinlay);
          spinner.setAdapter(adapter);

    }
});
forexch.show();//->this is the crash point

}
  }

我猜有更好的方法来实现对话。 该功能主要检查这是否是应用程序第一次启动，如果是，则弹出一个对话框选择基础货币

forexch.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);

并使用此权限：

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

---

这不起作用，在我更新android studio之前它一直在工作，这是错误->，java.lang.RuntimeException:无法启动活动组件信息{com.spendo.sam.spendo/com.spendo.sam.spendo.mainscreen}：android.view.WindowManager$BadTokenException:无法添加窗口android.view.ViewRootImpl$W@c63bde6--窗口类型2003的权限被拒绝

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

final Dialog forexch =new Dialog(getApplicationContext());//-> dialog initiated