Question

我声明了一个名为var progressBar的UIView变量：UIView？

我用它显示或隐藏视图

func showProgressBar(showBar: Bool){
if showBar{
            let viewHeight = view.frame.size.height
            progressBar = Bundle.main.loadNibNamed("progressBar", owner: nil, options: nil)?.first as? UIView
            progressBar?.frame = CGRect(x: 0, y: viewHeight - 80 , width: self.view.frame.width, height: 80)
            if let bar = progressBar{
                self.view.addSubview(bar)
            }
        }else{
            DispatchQueue.main.async() {
                self.progressBar?.removeFromSuperview()
            }
        }

有时当我在视图之间稍微导航时，即使执行self.progressBar?.removeFromSuperview()，我也无法隐藏进度条。在我看来，如果视图丢失了对旧进度条的引用...你对这个问题以及如何修复它有所了解吗？

Answer 1

如果您两次调用showProgressBar，则不会验证是否已存在任何栏，因此您可能会添加第二个并丢失对第一个的引用。因此，当您删除它时，它只会删除第二个并且不起作用。

Answer 2

如果您只想显示和隐藏{ "name": "rats-gui", "version": "0.0.0", "license": "MIT", "angular-cli": {}, "scripts": { "ng": "ng", "start": "ng serve", "test": "ng test", "pree2e": "webdriver-manager update --standalone false --gecko false", "e2e": "protractor" }, "private": true, "dependencies": { "@angular/animations": "^4.2.4", "@angular/common": "^4.2.4", "@angular/compiler": "^4.2.4", "@angular/compiler-cli": "^4.2.4", "@angular/core": "^4.2.4", "@angular/forms": "^4.2.4", "@angular/http": "^4.2.4", "@angular/material": "^2.0.0-beta.7", "@angular/platform-browser": "^4.2.4", "@angular/platform-browser-dynamic": "^4.2.4", "@angular/platform-server": "^4.2.4", "@angular/router": "^4.2.4", "@types/lodash": "ts2.0", "angular2-datatable": "0.5.3", "core-js": "^2.4.1", "hammerjs": "^2.0.8", "lodash": "^4.17.4", "rxjs": "^5.0.1", "ts-helpers": "^1.1.1", "typescript": "^2.3.4", "zone.js": "^0.8.4" }, "devDependencies": { "@angular/compiler-cli": "^4.2.4", "@types/jasmine": "2.5.38", "@types/node": "^6.0.42", "angular-cli": "1.0.0-beta.28.3", "codelyzer": "~2.0.0-beta.1", "jasmine-core": "2.5.2", "jasmine-spec-reporter": "2.5.0", "karma": "1.2.0", "karma-chrome-launcher": "^2.0.0", "karma-cli": "^1.0.1", "karma-jasmine": "^1.0.2", "karma-remap-istanbul": "^0.2.1", "protractor": "~4.0.13", "ts-node": "1.2.1", "tslint": "^4.3.0", "typescript": "2.1.5" } }，为什么不使用progressBar？通过这样做，您可以在不再使用它时创建self.progressBar.hidden = true/false一次和progressBar。

removeFromSuperview

removeFromSuperview（）并不总是有效

2 个答案: