javascript - 如何使用 WinJS 在 Windows Phone 8.1 中保存图像

Question

我希望使用 WinJS 将我的 Windows 8 应用程序迁移到 Windows Phone 8.1。我在 Windows 8 中使用了 picker.pickSaveFileAsync，WP 8.1 不支持该功能。

然后我引用了 http://code.msdn.microsoft.com/windowsapps/Simple-Imaging-Sample-a2dec2b0 的官方样本

单击“另存为”按钮时，示例中的 Javascript 版本不会在 Windows Phone 8.1 上保存，并且在调用“getFileAsync”时返回以下错误:

0x80004005 - JavaScript runtime error: Unspecified error

单击“保存”时，会返回只读错误。我也在 Lumia 520 中测试了该样本。我在手机上也遇到同样的错误。

Answer 1

在 Windows Phone 中，您无法获得对从 FileOpenPicker 返回的文件的写访问权限。您必须使用 FileSavePicker 来执行此操作。在同事的帮助下，我获得了一个示例工作，可以从“空白”Windows Phone 应用程序模板开始打开文件，然后以新名称重新保存文件

在 default.html 中创建两个按钮:

<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，请确保设置 ImageProperties在保存之前获取它。

很抱歉 sample 损坏了，我会将其报告给 sample 所有者。