android - 延迟效果很好；稍作修改，没有延迟——为什么？

Question

此代码包含在 QuizFragment.java 中，延迟 ms 毫秒，然后执行 loadNextFlag。工作正常。 (毫秒 = 2000 毫秒)

public void pauseAndThenShowNextFlag(long ms){
    showTimer("pauseAndThenShowNextFlag");
    pauseTimer(); // 7/17/15--DAS
    handler.postDelayed
            (
                    new Runnable() {
                        @Override
                        public void run() {
                            loadNextFlag();
                        }
                    }, ms       // ms-second delay
            );
    startTimer();
}

我将延迟更改为在另一个对象中，所以上面变成了:

public void pauseAndThenShowNextFlag(long ms){
    showTimer("pauseAndThenShowNextFlag");
    Timer.xhaltTimer4(ms);
    loadNextFlag();
    startTimer();
}

这是 Timer.java 中的 xhaltTimer4:

public static void xhaltTimer4(long ms){
    customHandler.postDelayed
            (
                    new Runnable() {
                        @Override
                        public void run() {
                            pauseTimer();
                        }
                    }, ms); // 2000 milliseconds for 2-second delay
}

绝对不会出现延迟。是不是因为 loadNextFlag 包含的代码比 pauseTimer 多很多？为什么会有所不同？根据 Runnable run 方法必须执行多少操作才能启用延迟，划定的界线在哪里？

我尝试了修改后的 xhaltTimer4——仍然没有延迟:

public static void xhaltTimer4(long ms){
    Handler h = new Handler();
    h.postDelayed
            (
                    new Runnable() {
                        @Override
                        public void run() {
                            pauseTimer();
                        }
                    }, ms); // ms-millisecond delay
}

这是pauseTimer:

public static void pauseTimer(){
    timeSwapBuff += timeInMilliseconds;
    customHandler.removeCallbacks(updateTimerThread);
}

这是loadNextFlag:

public void loadNextFlag() {
    startTimer();
    String timerDisplayString;
    oneImageView.setVisibility(View.INVISIBLE);
    showTimer("loadNextFlag");
    currentTimeSpent = timeStringToMillis(Timer.getTimerString());// was prevTimeSpent--7/17/15--DAS
    InputStream stream ;
    // get file name of the next flag and remove it from the list
    consecutiveWrong = 0;

    String nextImage = quizFlagPathList.remove(0);
    correctAnswer = nextImage; // update the correct answer
    answerImageView.setVisibility(View.INVISIBLE);
    ableButtons(true);

    // display current question number--2nd and 3rd parameters are INPUT into the xml statement
    questionNumberTextView.setText(getResources().getString(R.string.question,
            (correctAnswers + 1),
            FLAGS_IN_QUIZ));
    // extract the region from the next image's name
    String region = nextImage.substring(0, nextImage.indexOf('-'));

    // use AssetManager to load next image from assets folder
    AssetManager assets = getActivity().getAssets();

    try{
        stream = assets.open(region + "/" + nextImage + ".png");

        Drawable flag = Drawable.createFromStream(stream, nextImage);
        flagImageView.setImageDrawable(flag);
    }catch (IOException exception){Log.w(TAG, "Error loading " + nextImage, exception);}

    Collections.shuffle(flagPathList); // shuffle file names

    // put the correct answer at the end of flagPathList
    int correct = flagPathList.indexOf(correctAnswer);

    flagPathList.add(flagPathList.remove(correct));

    int k = 0;
    countriesToUse.clear();
    for(int row = 0; row < guessRows; row++)
        for (int col = 0; col < guessLinearLayouts[row].getChildCount(); col++)
            countriesToUse.add(getCountryName(flagPathList.get(k++)));

    countriesToUse.set(countriesToUse.size() - 1, getCountryName(flagPathList.get(flagPathList.size() - 1)));

    if(MainActivity.getAlphabetize()) Collections.sort   (countriesToUse);
    else                              Collections.shuffle(countriesToUse);

    k = 0;
    // add 3, 6, or 9 guess Buttons based on the value of guessRows
    for (int row = 0; row < guessRows; row++) {
        // place Buttons in currentTableRow
        for (int column = 0; column < guessLinearLayouts[row].getChildCount(); column++) {
            // get reference to Button to configure
            Button newGuessButton = (Button) guessLinearLayouts[row].getChildAt(column);
            newGuessButton.setEnabled(true);
            // get country name and set it as newGuessButton's text
            String fileName = countriesToUse.get(k++);
            newGuessButton.setText((fileName));
        }
    }
} // end method loadNextFlag

Answer 1

这是因为xhaltTimer4是同步方法调用，不会等待ms。在这里面你发布了一个 Runnable，它将在一些延迟后运行。您应该尝试将 loadNextFlag() 移动到 runnable 的 run() 方法中，如下所示

public static void xhaltTimer4(long ms){
    Handler h = new Handler();
    h.postDelayed
            (
                    new Runnable() {
                        @Override
                        public void run() {
                            pauseTimer();
                            loadNextFlag()
                        }
                    }, ms); // ms-millisecond delay
}