android - FragmentManager.executePendingTransactions 不会立即调用 onCreateView()

Question

我目前正在尝试以编程方式添加一个 fragment ，该 fragment 具有一个我需要在 fragment 创建后立即初始化的 View 。我尝试在 FragmentTransition.commit() 之后立即使用 FragmentManager.executePendingTransactions()，但它无法正常工作。我做了一个研究，发现 this ，所以我意识到 FragmentManager.executePendingTransactions() 在 onCreate() 中不起作用，然后将代码放入 onStart()，但它仍然不起作用。虽然在我的例子中它是从 onItemClickListener() 调用的，但我认为它没有任何区别。这是我的代码:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.vk_music_list);
    musicProgressBar = new MusicProgressBar();
    listView = (ListView) findViewById(R.id.listView);
}

@Override
protected void onStart() {
    super.onStart();
    listView.setOnItemClickListener(this);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    String audioUrl = ((VKApiAudio) parent.getAdapter().getItem(position)).url;
    serviceIntent.putExtra("audioUrl", audioUrl);

    //Inflate music progress bar
    fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragment = fragmentManager.findFragmentById(R.id.musicBarContainer);
    if(fragment == null) {
        fragmentTransaction.add(R.id.musicBarContainer, musicProgressBar)
                .setTransition(R.anim.move_from_the_bottom)
                .commit();
    }

    //This guy doesn't work
    fragmentManager.executePendingTransactions();

    //Never get into this, because fragment is always == null
    if(fragment != null) {
        SeekBar seekBar = (SeekBar) fragment.getView().findViewById(R.id.progressBar);
        seekBar.setMax(((VKApiAudio) parent.getAdapter().getItem(position)).duration);
    }
    startService(serviceIntent);
}

Answer 1

好吧，我终于找到问题所在了。问题的原因是 fragmentTransaction.commit() 和 fragmentManager.executePendingTransactions() 都没有更改存储在 fragment 变量中的引用。因此，在 executePendingTransactions() 之后，我需要再次调用 findFragmentById()，因此它存储的引用将引用创建的 fragment 。这是一个工作代码:

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    String audioUrl = ((VKApiAudio) parent.getAdapter().getItem(position)).url;
    serviceIntent.putExtra("audioUrl", audioUrl);

    //Inflate music progress bar
    fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragment = fragmentManager.findFragmentById(R.id.musicBarContainer);
    if(fragment == null) {
        fragmentTransaction.add(R.id.musicBarContainer, musicProgressBar)
                .commit();
    }

    //Force to create fragment without scheduling so it's not necessarily to wait until it get scheduled
    fragmentManager.executePendingTransactions();

    //This is what I needed
    fragment = fragmentManager.findFragmentById(R.id.musicBarContainer);

    //Set song duration as a seekBar's maximum
        if (fragment != null) {
            SeekBar seekBar = (SeekBar) fragment.getView().findViewById(R.id.progressBar);
            seekBar.setMax(((VKApiAudio) parent.getAdapter().getItem(position)).duration);
        }
    startService(serviceIntent);
}

希望对大家有所帮助。