Android:将数据(附加内容)传递给片段

Question

我是Android编程的新手,在将Parcelable的ArrayList传递给片段时遇到了问题.这是启动的Activity(运行良好!),其中feedlist是可分割音乐的ArrayList .

Intent in = new Intent(context, ListMusicsActivity.class);

in.putExtra("arrayMusic", feedList);
activity.startActivity(in);

片段Activity onCreate()方法:

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activitymusiclist);

    if(savedInstanceState != null)
    {
        ListMusicFragment frag = new ListMusicFragment();
        frag.setArguments(getIntent().getExtras());
    }
}

片段代码:

public class ListMusicFragment extends SherlockFragment{

private ArrayList<Music> listMusics = new ArrayList<Music>();
private ListView listMusic;


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
    Bundle savedInstanceState)
{
    listMusics = (ArrayList<Music>) getArguments().getSerializable("arrayMusic");
    View view = inflater.inflate(R.layout.musiclistview, container, false);
    listMusic = (ListView) view.findViewById(R.id.musicListView);
    listMusic.setAdapter(new MusicBaseAdapter(getActivity(), listMusics));

    return view;
}
}

我认为问题就在于此

listMusics = (ArrayList<Music>) getArguments().getSerializable("arrayMusic");

最后这是我的音乐课程:

public class Music implements Parcelable{

private String url;
private String artist;
private String title;
private String duration;
private String info_url;
private String lyrics;


public Music(String url, String artist, String title, 
    String duration, String lyrics, String info_url)
{
    this.url = url;
    this.artist = artist;
    this.title = title;
    this.duration = duration;
    this.lyrics = lyrics;
    this.info_url = info_url;
}

public Music(Parcel in)
{
    url = ParcelUtils.readString(in);
    artist = ParcelUtils.readString(in);
    title = ParcelUtils.readString(in);
    duration = ParcelUtils.readString(in);
    info_url = ParcelUtils.readString(in);
    lyrics = ParcelUtils.readString(in);
}

public String getUrl()
{
    return url;
}

public String getArtist()
{
    return artist;
}

public String getTitle()
{
    return title;
}

public String getDuration()
{
    return duration;
}

public String getLyrics()
{
    return lyrics;
}

public String getInfo()
{
    return info_url;
}

@Override
public int describeContents() {
    return 0;
}


@Override
public void writeToParcel(Parcel dest, int flags)
{
    ParcelUtils.writeString(dest, url);
    ParcelUtils.writeString(dest, artist);
    ParcelUtils.writeString(dest, title);
    ParcelUtils.writeString(dest, duration);
    ParcelUtils.writeString(dest, lyrics);
    ParcelUtils.writeString(dest, info_url);
}

public static final Parcelable.Creator<Music> CREATOR = 
    new Parcelable.Creator<Music>() {

    public Music createFromParcel(Parcel in)
    {
        return new Music(in);
    }

    public Music[] newArray(int size)
    {
        return new Music[size];
    }
};
}

当我运行此代码时,我得到的问题是Fragment onCreateView()方法中的java.lang.NullPointerException.如果有人指出我正确的方向,看到我失败的地方,我会非常感激.

编辑:问题解决了:我只需要将这一行添加到片段Activity onCreate()方法中(另外getArguments()将返回null):

getSupportFragmentManager().beginTransaction()
    .add(android.R.id.content, frag).commit();

并将其添加到片段代码中:

@Override
    public void onActivityCreated(Bundle savedInstanceState)
{
    super.onActivityCreated(savedInstanceState);

    Bundle bundle = getArguments();
    if(bundle != null)
    {
        listMusics = bundle.getParcelableArrayList("arrayMusic");
        listMusic.setAdapter(new MusicBaseAdapter(getActivity(), listMusics));
    }
}

其中,listMusics是ArrayList的Parcelable音乐.

Answer 1

两件事情.首先,我不认为您正在添加要正确传递给片段的数据.您需要传递给片段的是捆绑,而不是意图.例如,如果我想要向int片段发送值,我将创建一个包,将其int放入该包中,然后将该包设置为在创建片段时使用的参数.

Bundle bundle = new Bundle();
bundle.putInt(key, value);
fragment.setArguments(bundle);

第二,检索您需要获取发送到片段的参数的信息.然后,您可以根据您使用的密钥提取值.例如在你的片段中:

Bundle bundle = this.getArguments();
if (bundle != null) {
    int i = bundle.getInt(key, defaulValue);
}

你得到的变化取决于你放的东西.此外,默认值通常null但不是必须的.这取决于您是否为该参数设置了默认值.

最后我认为你不能做到这一点onCreateView.我认为你必须在片段的onActivityCreated方法中检索这些数据.我的推理如下.onActivityCreated在底层活动完成自己的onCreate方法之后运行.如果您在活动的onCreate方法中将要检索的信息放在捆绑中,则在片段期间它将不存在onCreateView.尝试使用此功能,稍后再onActivityCreated更新您的ListView内容.