当我在外部应用程序中更改.docx文件的内容时，FileObserver不会触发MODIFY事件

Question

在MainActivity.class内，我在手机上引用了.docx文件

//Reference to the file
File targetFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/storage/sdcard0/My Folder/Android-tutorial.docx");

//I start the background service here.
startService(new Intent(getApplicationContext(), FileObserverService.class).putExtra("INTENT_EXTRA_FILEPATH", targetFile.getAbsolutePath()));

//To open file in external app
Uri targetUri = Uri.fromFile(targetFile);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(targetUri, "application/*");
startActivityForResult(intent, 100);

“我的服务”类用于监视文件更改。在外部应用程序中打开.docx文件时，仅会触发OPEN事件。即使更改文件内容并将其从外部应用程序保存，也不会触发MODIFY事件。

public class FileObserverService extends Service {
    private FileObserver mFileObserver;

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        try {
            final String pathToFile = intent.getStringExtra("INTENT_EXTRA_FILEPATH");
            new FileObserver(pathToFile) {
                @Override
                public void onEvent(int event, String path) {
                    switch (event) {
                        case FileObserver.OPEN:
                            Log.d("FILEOBSERVER_OPEN", "Event with id " + Integer.toHexString(event) + " happened");
                            break;
                        case FileObserver.MODIFY:
                            Log.d("FILEOBSERVER_MODIFY", "Event with id " + Integer.toHexString(event) + " happened");
                            break;
                        case FileObserver.CLOSE_WRITE:
                            Log.d("FILEOBSERVER_CLOWRITE", "Event with id " + Integer.toHexString(event) + " happened");
                            break;
                        case FileObserver.DELETE:
                            Log.d("FILEOBSERVER_DELETE", "Event with id " + Integer.toHexString(event) + " happened");
                            break;
                    }
                }
            }.startWatching();
        }catch (Exception e){
            e.printStackTrace();
        }
        return Service.START_STICKY;
    }

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public IBinder onBind(Intent intent) {
        //TODO for communication return IBinder implementation
        return null;
    }
}

输出：

D/FILEOBSERVER_OPEN: Event with id 20 happened