添加到运行线程或等待线程完成后再执行下一个代码

Question

我有一个线程正在后台下载图像，需要它在上传开始前完成。我有一个开始上传的按钮，但不确定如何检查我的第一个线程是否完成/等待它完成。

这是我的下载线程：

 t = new Thread(new Runnable() {
    // NEW THREAD BECAUSE NETWORK REQUEST WILL BE MADE THAT WILL BE A LONG PROCESS & BLOCK UI
    // IF CALLED IN UI THREAD
    public void run() {
        try {
            for (int i = 0; i < Constants2photo.IMAGES.size(); i++) {

                Uri myUri = Uri.parse(Constants2photo.IMAGES.get(i).get("url"));
                String fileLocation = loadPicasaImageFromGallery(myUri);
                Constants2photo.IMAGES.get(i).put("fileLocation", fileLocation);
                System.out.println("fileloc: " + fileLocation);

            }
            System.out.println("done getting files - " + Constants2photo.IMAGES);

            //this part would download the image to the media store//TODO add this to a background task so sending event is faster.
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
});
t.start();

threads.add(t); //this is a List

以上代码只是在我的class

中的onactivityresult方法中

我的按钮代码与线程 #2 需要在 t 完成后启动：

public void submitPhotos(View view){
 //convert and submit photos here

    Thread t2 = new Thread(new Runnable() {
        // NEW THREAD BECAUSE NETWORK REQUEST WILL BE MADE THAT WILL BE A LONG PROCESS & BLOCK UI
        // IF CALLED IN UI THREAD
        public void run() {
            try {

                for (int i = 0; i < Constants2photo.IMAGES.size(); i++) {


                  ...
                    System.out.println("encoded string: " + encodedString);

                }

            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    });
    t2.start();

那么我在哪里使用 join 使 t2 仅在 t 完成时才执行？

Answer 1

Thread.join() 是 m0skit0 提到的正确解决方案。忽略 his/her 关于不生成线程的评论。如果您想让 UI 保持对其他目的的响应，并且只想在此线程完成后激活上传按钮，那么 join() 是您的解决方案。

添加到运行线程或等待线程完成后再执行下一个代码

Add to a running thread or wait for thread to finished before executing next code

java

multithreading

android

添加到 运行 线程或等待线程完成后再执行下一个代码

Add to a running thread or wait for thread to finished before executing next code

java

multithreading

android

添加到运行线程或等待线程完成后再执行下一个代码