java - 如何在 Android 中取消 AsyncTask

Question

在我的应用程序中，我有 2AsyncTask种方法，我想什么时候activity去onPause取消这个AsyncTasks 并onResume 从头开始。
我写下面的代码，我按下主页按钮和应用程序转到onPause并从最近的应用程序再次打开这个应用程序
我的意思是打电话onPause和onResume！

但是当应用程序再次运行时（从最近的应用程序），调用onResume但不是从头AsyncTask开始！

我的代码：

@Override
protected void onResume() {
    super.onResume();
    new Handler(getMainLooper()).postDelayed(() -> {
        //Get compress or upload
        if (bundle == null) {
            //Get video from file
            getLoadOriginalVideos();
            testIsSendPlans = testId;
        }
    }, 500);
}

@Override
protected void onPause() {
    super.onPause();
    new GetOriginalVideosAsync().cancel(true);
    new GetCompressedVideosAsync().cancel(true);
}

private void getLoadOriginalVideos() {
    if (videoList.isEmpty()) {
        File directory = new File(Environment.getExternalStorageDirectory() + File.separator + APPDIR);
        ArrayList<File> filesList = new ArrayList<File>();
        if (directory.isDirectory() && directory.exists()) {
            filesList.addAll(Arrays.asList(getOriginalVideos(directory.listFiles())));
        }
        new GetOriginalVideosAsync().execute(filesList.toArray(new File[filesList.size()]));
    }
}

@SuppressLint("StaticFieldLeak")
class GetOriginalVideosAsync extends AsyncTask<File[], Integer, ArrayList<Video>> {
    File[] files;
    ContentResolver resolver;

    GetOriginalVideosAsync() {
        resolver = context.getContentResolver();
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(ArrayList<Video> videos) {
        Collections.sort(videos, Collections.reverseOrder());
        getLastOriginalVideo(addVideos(videos));
    }

    private ArrayList<Video> addVideos(ArrayList<Video> videos) {
        return new ArrayList<>(videos);
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);

    }

    @Override
    protected ArrayList<Video> doInBackground(File[]... arg) {
        files = arg[0];
        for (File file : files) {
            if (!file.isDirectory() && isVideoFile(file.getPath())) {
                videoList.add(new Video(file.getName(), file, new Date(file.lastModified())));
            }
        }
        return videoList;
    }
}

@SuppressLint("StaticFieldLeak")
class GetCompressedVideosAsync extends AsyncTask<File[], Integer, ArrayList<Video>> {
    File[] files;
    ContentResolver resolver;

    GetCompressedVideosAsync() {
        resolver = context.getContentResolver();
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(ArrayList<Video> videos) {
        Collections.sort(videos, Collections.reverseOrder());
        getLastCompressedVideo(addVideos(videos));
    }

    private ArrayList<Video> addVideos(ArrayList<Video> videos) {
        return new ArrayList<>(videos);
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);

    }

    @Override
    protected ArrayList<Video> doInBackground(File[]... arg) {
        files = arg[0];
        for (File file : files) {
            if (!file.isDirectory() && isVideoFile(file.getPath())) {
                videoListCompressed.add(new Video(file.getName(), file, new Date(file.lastModified())));
            }
        }
        return videoListCompressed;
    }
}

我该如何解决它并从头onResume 开始？AsyncTask

标签： javaandroidandroid-asynctaskandroid-thread

Answer 1

当你取消 asynctask 时，虽然它被取消了。您的 asyncTask 将继续运行，直到 doInBackGround() 完成其工作。

所以为了你GetOriginalVideosAsync这样做doInBackground：

@Override
protected ArrayList<Video> doInBackground(File[]... arg) {
files = arg[0];
for (File file : files) {

//add this

if(isCancelled){

return null;

}

if (!file.isDirectory() && isVideoFile(file.getPath())) {
videoList.add(new Video(file.getName(), file, new Date(file.lastModified())));
}

}
return videoList;
}

并为您GetCompressedVideosAsync执行此操作doInBackground：

@Override
protected ArrayList<Video> doInBackground(File[]... arg) {
files = arg[0];
for (File file : files) {

//add this    
if(isCancelled){
return null;
}

if (!file.isDirectory() && isVideoFile(file.getPath())) {
videoListCompressed.add(new Video(file.getName(), file, new Date(file.lastModified())));

}

}
return videoListCompressed;
}

更新

在我告诉你的同一个地方尝试这两个任务：

if(isCancelled){
break;
}

更新 2

看你的 asyncTaks 必须是活动的成员变量

class MyActivity extends ........{

private GetOriginalVideosAsync orginalTask;
private GetCompressedVideosAsync compressedTask;
.......



}

像这样调用暂停：

@Override
protected void onPause() {

    orginalTask.cancel(true);
    compressedTask.cancel(true);
    super.onPause();

}

和

private void getLoadOriginalVideos() {
    if (videoList.isEmpty()) {
        File directory = new File(Environment.getExternalStorageDirectory() + File.separator + APPDIR);
        ArrayList<File> filesList = new ArrayList<File>();
        if (directory.isDirectory() && directory.exists()) {
            filesList.addAll(Arrays.asList(getOriginalVideos(directory.listFiles())));
        }
     orginalTask =   new GetOriginalVideosAsync();

    orginalTask.execute(filesList.toArray(new File[filesList.size()]));
    }
}