显示对拖放的响应的工作表

Question

我正在实现拖放，并且有一种情况，我需要用户决定如何响应拖放。我想要打开一个表单来请求用户输入。问题是，直到我将另一个项目拖到同一视图时，工作表才出现。这确实有意义，所以我正在寻找一种不同的方法来处理这个问题。

当前的方法是这样的(简化):

struct SymbolInfo {
enum SymbolType {
case string, systemName
}

var type: SymbolType
var string: String
}
struct MyView: View, DropDelegate {
@State var sheetPresented = false
@State var droppedText = ""
static let dropTypes = [UTType.utf8PlainText]
var textColor = NSColor.white
private var frameRect: CGRect = .null
private var contentPath: Path = Path()
private var textRect: CGRect = .null
@State private var displayOutput: SymbolInfo
@State private var editPopoverIsPresented = false
// There's an init to set up the display output, the various rects and path
var body: some View {
ZStack(alignment: stackAlignment) {
BackgroundView() // Draws an appropriate background
.frame(width: frameRect.width, height: frameRect.height)
if displayOutput.type == .string {
Text(displayOutput.string)
.frame(width: textRect.width, height: textRect.height, alignment: .center)
.foregroundColor(textColour)
.font(displayFont)
.allowsTightening(true)
.lineLimit(2)
.minimumScaleFactor(0.5)
}
else {
Image(systemName: displayOutput.string)
.frame(width: textRect.width, height: textRect.height, alignment: .center)
.foregroundColor(textColour)
.minimumScaleFactor(0.5)
}
}
.onAppear {
// Retrieve state information from the environment
}
.focusable(false)
.allowsHitTesting(true)
.contentShape(contentPath)
.onHover { entered in
// Populates an inspector
}
.onTapGesture(count: 2) {
// Handle a double click
}
.onTapGesture(count: 1) {
// Handle a single click
}
.popover(isPresented: $editPopoverIsPresented) {
// Handles a popover for editing data
}
.onDrop(of: dropTypes, delegate: self)
.sheet(sheetPresented: $sheetPresented, onDismiss: sheetReturn) {
// sheet to ask for the user's input
}
}
func sheetReturn() {
// act on the user's input
}
func performDrop(info: DropInfo) -> Bool {
if let item = info.itemProviders(for: dropTypes).first {
item.loadItem(forTypeIdentifier: UTType.utf8PlainText.identifier, options: nil) { (textData, error) in
if let textData = String(data: textData as! Data, encoding: .utf8) {
if (my condition) {
sheetIsPresented = true
droppedText = textData
}
else {
// handle regular drop
}
}
}
return true
}
return false
}
}

所以我的理由是，拖放设置sheetpresent为true，但它不会得到行动，直到视图被重建，比如在拖动其他东西到它。但我对SwiftUI还是个新手，所以我可能说错了。

有没有我还没找到的方法来处理这种交互?

Answer 1

我从来没有能够准确地重现这个问题，但这个问题与尝试根据条件显示多种类型的工作表有关。解决方案是将原始视图分解为包含不同行为的一系列视图，并显示适当的视图，而不是试图让一个视图做所有事情。

我不会展示整个代码，因为它在应用程序中嵌入得太深了，但这里有一个正常工作的演示应用程序:

import SwiftUI
import UniformTypeIdentifiers
@main
struct DragAndDropSheetApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
struct ContentView: View {
var body: some View {
HStack() {
TargetView(viewType: .normal, viewText: "A")
.frame(width: 40, height: 40, alignment: .top)
TargetView(viewType: .protected, viewText: "B")
.frame(width: 40, height: 40, alignment: .top)
TargetView(viewType: .normal, viewText: "C")
.frame(width: 40, height: 40, alignment: .top)
TargetView(viewType: .protected, viewText: "D")
.frame(width: 40, height: 40, alignment: .top)
}
.padding()
}
}
enum ViewType {
case normal, protected
}
struct TargetView: View, DropDelegate {
@State private var sheetPresented = false
@State var viewType: ViewType
@State var viewText: String
@State private var dropText = ""
@State private var dropType: DropActions = .none
static let dropTypes = [UTType.utf8PlainText]

var body: some View {
ZStack(alignment: .center) {
Rectangle()
.foregroundColor(viewType == .normal ? .blue : .red)
Text(viewText)
.foregroundColor(.white)
.frame(width: nil, height: nil, alignment: .center)
}
.focusable(false)
.allowsHitTesting(true)
.onDrop(of: TargetView.dropTypes, delegate: self)
.sheet(isPresented: $sheetPresented, onDismiss: handleSheetReturn) {
ProtectedDrop(isPresented: $sheetPresented, action: $dropType)
}
}

func handleSheetReturn() {
switch dropType {
case .append:
viewText += dropText

case .replace:
viewText = dropText

case .none:
// Nothing to do
return
}
}

func performDrop(info: DropInfo) -> Bool {
if let item = info.itemProviders(for: TargetView.dropTypes).first {
item.loadItem(forTypeIdentifier: UTType.utf8PlainText.identifier, options: nil) { textData, error in
if let textData = String(data: textData as! Data, encoding: .utf8) {
if viewType == .normal {
viewText = textData
}
else {
dropText = textData
sheetPresented = true
}
}
}
return true
}
return false
}
}
enum DropActions: Hashable {
case append, replace, none
}
struct ProtectedDrop: View {
@Binding var isPresented: Bool
@Binding var action: DropActions
var body: some View {
VStack() {
Text("This view is protected. What do you want to do?")
Picker("", selection: $action) {
Text("Append the dropped text")
.tag(DropActions.append)
Text("Replace the text")
.tag(DropActions.replace)
}
.pickerStyle(.radioGroup)
HStack() {
Spacer()
Button("Cancel") {
action = .none
isPresented.toggle()
}
.keyboardShortcut(.cancelAction)
Button("OK") {
isPresented.toggle()
}
.keyboardShortcut(.defaultAction)
}
}
.padding()
}
}