java - 无法获取 fragment 中的参数

Question

我遇到了不便，希望我能提供帮助。我有一个扩展 Fragment 的类，您在其中创建了一个实例来接收参数

public class FragmentPlaySong extends Fragment  {

....

private ArrayList<Song> songList;
private int randomList = 0;
private int currentSongPosition = 0;

....


public static FragmentPlaySong newInstance(ArrayList<Song> songList, int randomList, int position){
    FragmentPlaySong fragmentPlaySong = new FragmentPlaySong();
    Bundle args = new Bundle();
    args.putSerializable("songs",songList);
    args.putInt("randomList",randomList);
    args.putInt("position",position);
    fragmentPlaySong.setArguments(args);
    return fragmentPlaySong;
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    final View view = inflater.inflate(R.layout.fragment_play_song, container, false);

    ......

    return view;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    songList = (ArrayList<Song>) getArguments().getSerializable("songs");
    randomList = getArguments().getInt("randomList");
    currentSongPosition = getArguments().getInt("position");
}

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

}

我有 Activity 类，我可以通过 ListView 中的事件单击调用 Fragment

public class MainActivity extends Activity {

private ListView lstSong;    
private ArrayList<Song> songs = new ArrayList<Song>();
private int randomList = 0;    

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

    ....

    lstSong = (ListView) findViewById(R.id.lstsong);

    lstSong.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
            FragmentPlaySong fragmentPlaySong = new FragmentPlaySong();
            fragmentPlaySong.newInstance(songs,randomList,position);                
            getFragmentManager().beginTransaction().replace(R.id.FrgPlaySong, fragmentPlaySong).commit();
        }
    });        
}

....

}

如上所述，我提出调用 Fragment 的问题，它会生成错误，特别是在调用 Fragment 的 onCreate 事件时

10-14 16:52:37.291  20744-20744/pe.com.mkella.simpleamp E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: pe.com.mkella.simpleamp, PID: 20744
java.lang.RuntimeException: Unable to start activity ComponentInfo{pe.com.mkella.simpleamp/pe.com.mkella.simpleamp.MainActivity}: android.view.InflateException: Binary XML file line #31: Error inflating class fragment
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
        at android.app.ActivityThread.access$800(ActivityThread.java:144)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5146)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)

对于这一切，我注意到删除 Fragmen 的 onCreate 方法我没有错误，但无法获取参数的值。

非常感谢您的帮助。

PD:抱歉我的英语不好

Answer 1

这是您的问题:

FragmentPlaySong fragmentPlaySong = new FragmentPlaySong();
fragmentPlaySong.newInstance(songs,randomList,position);                

您的 newInstance() 方法返回一个 FragmentPlaySong 实例。因此，本质上，在这一行中，您分配了一个新的 FragmentPlaySong 实例并将其丢弃。相反，捕获该结果并使用该实例:

FragmentPlaySong fragment = FragmentPlaySong.newInstance(songs, randomList, position);