如何使用WinJS在Windows Phone 8.1中保存图像

Question

我希望使用WinJS将Windows 8应用程序迁移到Windows Phone 8.1。 我在Windows 8中使用了picker.pickSaveFileAsync ，但WP 8.1不支持。

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

单击“另存为”按钮时，示例中的Javascript版本不会保存在Windows Phone 8.1上，并且在调用`getFileAsync时，它将返回以下错误：

0x80004005-JavaScript运行时错误：未指定的错误

当点击保存时，它返回一个只读错误。 我也在Lumia 520中测试了样品。 我在电话中遇到了同样的错误。

Answer 1

在Windows Phone中，您无法获得对从FileOpenPicker返回的文件的写访问权。 您必须使用FileSavePicker来执行此操作。 在同事的帮助下，我获得了可以打开的示例工作，然后从“空白” Windows Phone应用程序模板开始以新名称重新保存文件。

在default.html内部，创建两个按钮：

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

将default.js替换为以下内容：

(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();
})();

如果您自己创建文件，请确保在保存之前为其设置ImageProperties 。

抱歉，损坏的样品我会通知样品所有者。