我目前面临在定向更改后恢复ArrayList位置的错误，以增强用户体验。我尝试存储ArrayList并已经制作了movieData Parcelable。在方向更改后使用调试器时，savedInstance显然不是null并且包含一个int值，并且可能是parcelable Array List，我真的不知道为什么这段代码还没有工作。
片段类：
public class MovieGridFragment extends Fragment {
public clickInterfaceHelper clickListener;
private GridView movieGridView;
private int index;
public List<movieData> movieDataList = new ArrayList<>();
public ArrayList<movieData> restoreList;
public MovieGridFragment() {} //empty constructor
@Override
public void onAttach(Context context) {
super.onAttach(context);
}
public void setClickListener(clickInterfaceHelper listener) {
this.clickListener = listener;
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(savedInstanceState != null)
index = savedInstanceState.getInt("INDEX");
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
setHasOptionsMenu(true);
if(movieDataList.isEmpty() && networkChecker.isNetworkAvailableChecker(getContext())) {
movieDataList = new ArrayList<movieData>();
}
if(!movieDataList.isEmpty() && !networkChecker.isNetworkAvailableChecker(getContext())) {
movieDataList = new ArrayList<movieData>();
}
View rootView = inflater.inflate(R.layout.movie_display_fragment, container, false);
movieGridView = (GridView) rootView.findViewById(R.id.gv_movie_display);
if(savedInstanceState != null && savedInstanceState.containsKey("OLDMOVIEDATA")) {
//index = savedInstanceState.getInt("INDEX");
//movieDataList.addAll(Arrays.asList((movieData[]) savedInstanceState.getSerializable("OLDMOVIEDATA")));
restoreList = savedInstanceState.getParcelableArrayList("OLDMOVIEDATA");
movieAdapter adapter = new movieAdapter(getActivity(),restoreList);
adapter.notifyDataSetChanged();
//movieGridView.setAdapter(adapter);
movieGridView.smoothScrollToPosition(index);
}
else {
movieAdapter adapter = new movieAdapter(getActivity(), movieDataList);
adapter.notifyDataSetChanged();
movieGridView.setAdapter(adapter);
}
movieGridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if(clickListener != null)
clickListener.clickOnItem(position);
}
});
return rootView;
}
@Override
public void onSaveInstanceState(Bundle outState) {
//outState.putSerializable("OLDMOVIEDATA",movieData.movieDataArray);
outState.putParcelableArrayList("OLDMOVIEDATA",restoreList);
outState.putInt("INDEX",movieGridView.getFirstVisiblePosition());
super.onSaveInstanceState(outState);
}
}
适配器：
public class movieAdapter extends ArrayAdapter<movieData> {
public movieAdapter(Context context, List<movieData> movieObject) {
super(context, 0, movieObject);
}
public View getView(int pos, View convertingView, ViewGroup viewGroup) {
movieData movieDatas = getItem(pos);
String url="http://image.tmdb.org/t/p/w185"+movieDatas.getMovieImagePath();
if(convertingView == null)
convertingView = LayoutInflater.from(getContext()).inflate(R.layout.image_display,viewGroup,false);
ImageView imageView = (ImageView) convertingView.findViewById(R.id.iv_movie_image);
Picasso.with(getContext()).load(url.trim()).into(imageView);
return convertingView;
}
}
和主要活动：
public class MainActivity extends AppCompatActivity implements clickInterfaceHelper {
public static String sorterString = null;
public static String urlBase = "https://api.themoviedb.org/3/movie/";
public static String urlFinal = null;
RequestQueue requestQueue;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(savedInstanceState == null) {
MovieGridFragment fragment = new MovieGridFragment();
fragment.setClickListener(this);
getSupportFragmentManager().beginTransaction()
.add(R.id.activity_container, fragment)
.commit();
movieData.movieDataPosition = 0;
}
if(savedInstanceState != null) {
sorterString = savedInstanceState.getString("SORTER");
}
if(sorterString==null)
sorterString="popular?";
if(sorterString!="favorite" && sorterString!=null) {
if(networkChecker.isNetworkAvailableChecker(this)) {
movieRequest();
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main_menu_act, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if(id == R.id.m_popularity_action) {
if(sorterString != "popular?") {
sorterString = "popular?";
if(networkChecker.isNetworkAvailableChecker(this))
movieRequest();
}
return true;
}
if(id == R.id.m_action_voter) {
if(sorterString != "top_rated?") {
sorterString = "top_rated?";
if(networkChecker.isNetworkAvailableChecker(this))
movieRequest();
}
return true;
}
if(id == R.id.m_favorite_btn) {
if(sorterString != "favorite") {
SQLiteOpenHelper helper = new movieDataDbHelper(this);
SQLiteDatabase database = helper.getReadableDatabase();
Cursor cursor= database.query(movieDataContract.contractEntry.TABLE_NAME,
new String[] {
movieDataContract.contractEntry.ID,
movieDataContract.contractEntry.IMG_PATH},null,null,null,null,null);
if(cursor.getCount() == 0) {
Toast.makeText(this, "there are no favorite movies yet!",Toast.LENGTH_SHORT).show();
} else {
sorterString = "favorite";
showFavoriteFragment();
}
database.close();
helper.close();
cursor.close();
}
return true;
}
return super.onOptionsItemSelected(item);
}
public void showFavoriteFragment() {
favoriteMoviesDetailsFragment fragment = new favoriteMoviesDetailsFragment();
try {
getFragmentManager().beginTransaction().replace(R.id.activity_container,fragment).commit();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
outState.putString("SORTER", sorterString);
outState.putInt("POSITION",movieData.movieDataPosition);
super.onSaveInstanceState(outState, outPersistentState);
}
public void movieRequest() {
final MovieGridFragment gridFragment = new MovieGridFragment();
gridFragment.setClickListener(this);
urlFinal = urlBase + sorterString + movieData.apiKey;
urlFinal.trim();
requestQueue = Volley.newRequestQueue(this);
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, urlFinal, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
JSONArray array = response.getJSONArray("results");
movieData.movieDataArray = new movieData[array.length()];
for (int i = 0; i < array.length(); i++) {
movieData movie = new movieData();
JSONObject jsonObject = array.getJSONObject(i);
movie.setMovieId(jsonObject.getString("id"));
movie.setMovieImagePath(jsonObject.getString("poster_path"));
movie.setMovieTitle(jsonObject.getString("original_title"));
movie.setMoviePlot(jsonObject.getString("overview"));
movie.setMovieVoting(jsonObject.getString("vote_average"));
movie.setMovieReleaseDate(jsonObject.getString("release_date"));
movieData.movieDataArray[i] = movie;
}
gridFragment.movieDataList = Arrays.asList(movieData.movieDataArray);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.activity_container, gridFragment);
try {
transaction.commitAllowingStateLoss();
} catch (Exception e) {
e.printStackTrace();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e("volley", String.valueOf(error));
}
}
);
requestQueue.add(jsonObjectRequest);
}
@Override
public void clickOnItem(int id) {
movieData.movieDataPosition = id;
if(movieData.movieDataArray == null) {
movieRequest();
} else {
Intent intent = new Intent(this, detailsActivity.class);
intent.putExtra("FRAGMENT","MOVIE");
startActivity(intent);
}
}
@Override
public void favoriteMovieItem(int movieId) {
movieData.dbPosition = movieId;
Intent intent = new Intent(this,detailsActivity.class);
intent.putExtra("FRAGMENT","favorite");
startActivity(intent);
}
}
答案 0 :(得分：1)
您已使用
@Override
public void onSaveInstanceState(Bundle outState) {
//outState.putSerializable("OLDMOVIEDATA",movieData.movieDataArray);
outState.putParcelableArrayList("OLDMOVIEDATA",restoreList);
outState.putInt("INDEX",movieGridView.getFirstVisiblePosition());
super.onSaveInstanceState(outState);
}
只需使用它来存储您需要保存的位置。使用“onCreateView”中给出的包获取位置。
如果不起作用，请将“setRetainInstance（true）”放入片段的“onCreate”函数中。它会阻止你的片段被破坏，然后在方向改变时从零重建。 但是，我在某个地方读到了使用具有UI元素的片段的正确方法（但我从来没有发现任何错误）。
如果您想要另一种不使用“setRetainInstance”的方法，请存储（并恢复）活动中的位置
public void onSaveInstanceState(Bundle outState)"
功能。为此，在片段中创建一个函数“getPosition（）”，在活动saveInstanceState中调用它，并在片段中创建一个函数“refresh（int position）”（并在恢复的位置值上调用它）在活动中加载/重新创建。