Question

这是我要调用的函数：

function restoreCurrent() {
    var tzact = db.transaction(['Picture'],"readonly").objectStore("Picture").get(2);
    tzact.onerror = function(event) {
        alert ("Failed to retrieve the data.");
    }
    tzact.onsuccess = function(event) {
        document.getElementById("demo").innerHTML += "Transaction success.<br />";
    }
}
window.onload = function() {
    restoreCurrent();
}

如您所见，它应该在成功或错误时输出一些信息。实际上，它不输出任何内容。之后，我在.onsuccess函数中有更多代码，但是什么也没有执行。它停止工作的那一行是数据库调用，我已经测试了很多。作为记录，创建数据库时这两行代码

var tzact = db.transaction(['Picture'], "readwrite").objectStore("Picture").add({id : 2, pictureData : working});

以及当我尝试更新该特定记录时的这一行

var tzact = db.transaction(['Picture'], "readwrite").objectStore("Picture").put({id : 2, pictureData : working});

似乎可以执行OK或至少嵌入它们的功能可以继续输出成功消息。无法提取任何数据就很难确定。

编辑：自己弄清楚。答案是我必须将其放入每个函数中：

var request = window.indexedDB.open("[database name]",5);
request.onerror = function() {
    alert ("Failed to open the database.");
}
request.onsuccess = function() {
    var db = request.result;
    var tzact = db.transaction(['Picture'],"readonly").objectStore("Picture").get(2); // or "readwrite" and .put(2), as the case might be
    tzact.onerror=function() {
        alert ("Data transaction failed.");
    }
    tzact.onsuccess=function() {
        document.getElementById("demo").innerHTML += "Data transaction successful.<br />";
        if (tzact.result) {
            var working = tzact.result.pictureData;
            // the rest of the function goes here
        } else {
            alert ("No data received.");
        }
    }
}

无法从indexedDB中获取数据

0 个答案: