如何使用WinJS在Windows Phone 8.1中保存圖像

Question

我希望使用WinJS將Windows 8應用程序遷移到Windows Phone 8.1。 我在Windows 8中使用了picker.pickSaveFileAsync ，但WP 8.1不支持。

然后，我從http://code.msdn.microsoft.com/windowsapps/Simple-Imaging-Sample-a2dec2b0引用了官方示例

單擊“另存為”按鈕時，示例中的Javascript版本不會保存在Windows Phone 8.1上，並且在調用`getFileAsync時，它將返回以下錯誤：

0x80004005-JavaScript運行時錯誤：未指定的錯誤

當點擊保存時，它返回一個只讀錯誤。 我也在Lumia 520中測試了樣品。 我在電話中遇到了同樣的錯誤。

Answer 1

在Windows Phone中，您無法獲得對從FileOpenPicker返回的文件的寫訪問權。 您必須使用FileSavePicker來執行此操作。 在同事的幫助下，我獲得了可以打開的示例工作，然后從“空白” Windows Phone應用程序模板開始以新名稱重新保存文件。

在default.html內部，創建兩個按鈕：

<button id="choose">Choose a Photo</button>
<button id="save">Save a Photo</button>

將default.js替換為以下內容：

(function () {
    "use strict";

    var app = WinJS.Application;
    var activation = Windows.ApplicationModel.Activation;
    var origFile = null;

    function pickPhoto() {
        var picker = new Windows.Storage.Pickers.FileOpenPicker();
        var enumerator = Windows.Graphics.Imaging.BitmapDecoder.getDecoderInformationEnumerator();
        enumerator.forEach(function (decoderInfo) {
            decoderInfo.fileExtensions.forEach(function (fileExtension) {
                picker.fileTypeFilter.append(fileExtension);
            });
        });
        picker.pickSingleFileAndContinue();
    }

    function loadPhoto(file) {
        origFile = file;
    }

    function savePhotoPicker(file) {
        var picker = new Windows.Storage.Pickers.FileSavePicker();
        picker.fileTypeChoices.insert("JPEG file", [".jpg"]);
        picker.pickSaveFileAndContinue();
    }

    function savePhoto(src, dest) {
        src.copyAndReplaceAsync(dest).done(function () {
            console.log("success");
        })
    }

    app.onactivated = function (args) {
        if (args.detail.kind === activation.ActivationKind.launch) {
            if (args.detail.previousExecutionState !== activation.ApplicationExecutionState.terminated) {
                // TODO: This application has been newly launched. Initialize
                // your application here.
            } else {
                // TODO: This application has been reactivated from suspension.
                // Restore application state here.
            }
            args.setPromise(WinJS.UI.processAll());

            document.getElementById("choose").addEventListener("click", pickPhoto);
            document.getElementById("save").addEventListener("click", savePhotoPicker);
        }
        if (args.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.pickFileContinuation) {
            loadPhoto(args.detail.files[0]);
        }
        if (args.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.pickSaveFileContinuation) {
            savePhoto(origFile, args.detail.file);
        }
    };

    app.oncheckpoint = function (args) {
        // TODO: This application is about to be suspended. Save any state
        // that needs to persist across suspensions here. You might use the
        // WinJS.Application.sessionState object, which is automatically
        // saved and restored across suspension. If you need to complete an
        // asynchronous operation before your application is suspended, call
        // args.setPromise().
    };

    app.start();
})();

如果您自己創建文件，請確保在保存之前為其設置ImageProperties 。

抱歉，損壞的樣品我會通知樣品所有者。