Qt Quick Examples - Threading

线程 is a collection of QML multithreading examples.

运行范例

要运行范例从 Qt Creator ，打开欢迎模式，然后选择范例从范例。更多信息，拜访构建和运行范例 .

线程化 ListModel

Threaded ListModel 包含 ListView 和 ListModel 。 ListModel object is updated asynchronously in another thread, and the results propagate back to the main thread. A timer requests updates from the worker thread periodically:

        Timer {
            id: timer
            interval: 2000; repeat: true
            running: true
            triggeredOnStart: true
            onTriggered: {
                var msg = {'action': 'appendCurrentTime', 'model': listModel};
                worker.sendMessage(msg);
            }
        }

Inside the worker thread, the ListModel is synchronized once the data is finished loading:

WorkerScript.onMessage = function(msg) {
    if (msg.action == 'appendCurrentTime') {
        var data = {'time': new Date().toTimeString()};
        msg.model.append(data);
        msg.model.sync();   // updates the changes to the list
    }
}

WorkerScript

WorkerScript contains an example of using a WorkerScript to offload expensive calculations into another thread. This keeps the UI from being blocked. This example calculates numbers in Pascal's Triangle, and not in a very optimal way, so it will often take several seconds to complete the calculation. By doing this in a WorkerScript in another thread, the UI is not blocked during this time.

When the UI needs another value, a request is sent to the WorkerScript :

        Spinner {
            id: rowSpinner
            label: "Row"
            onValueChanged: {
                resultText.text = "Loading...";
                myWorker.sendMessage( { row: rowSpinner.value, column: columnSpinner.value } );
            }
        }

The workerscript then is free to take a really long time to calculate it:

WorkerScript.onMessage = function(message) {
    //Calculate result (may take a while, using a naive algorithm)
    var calculatedResult = triangle(message.row, message.column);
    //Send result back to main thread
    WorkerScript.sendMessage( { row: message.row,
                                column: message.column,
                                result: calculatedResult} );
}

When it's done, the result returns to the main scene via the WorkerScript 类型：

    WorkerScript {
        id: myWorker
        source: "workerscript.js"
        onMessage: {
            if (messageObject.row == rowSpinner.value && messageObject.column == columnSpinner.value){ //Not an old result
                if (messageObject.result == -1)
                    resultText.text = "Column must be <= Row";
                else
                    resultText.text = messageObject.result;
            }
        }
    }

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