当我旋转我的应用程序时，内容消失了，我有一个RecyclerView，其中有一个卡片列表，可以使用JSON和Web服务从外部数据库获取内容。我试图通过以下方式保存内容：
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if(items != null) {
outState.putParcelableArrayList("ITEMS", items);
items = null;
}
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
if (items == null) {
items = savedInstanceState.getParcelableArrayList("ITEMS");
recycler.setAdapter(adapter);
}
}
但仍然会出现同样的问题。
我的MainActivity.java文件：
public class MainActivity extends AppCompatActivity {
DrawerLayout drawerLayout;
Toolbar toolbar;
ActionBar actionBar;
Intent intent;
private SQLiteHandler db;
private SessionManager session;
private RecyclerView recycler;
private RecyclerView.Adapter adapter;
private RecyclerView.LayoutManager lManager;
private ProgressDialog pDialog;
JSONParser jParser;
private static final String TAG_SUCCESS = "success";
private static final String TAG_RECIPES = "recipes";
private static final String TAG_RECIPE_ID = "recipe_id";
private static final String TAG_NAME = "name";
private static final String TAG_USERNAME = "username";
private static final String TAG_PHOTO = "photo";
ArrayList<Recipe> items;
HashMap<String, String> user;
String uns;
TextView usernamesessionTV;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//uns = session.getUsername();
Intent i = getIntent();
if (i.hasExtra("user")) {
Bundle bd = getIntent().getExtras();
if (!bd.getString("user").equals(null) || bd.getString("user").trim().length() > 0) {
uns = bd.getString("user");
}
}
usernamesessionTV = (TextView) findViewById(R.id.navigation_view).findViewById(R.id.usernameSession);
items = new ArrayList<>();
new LoadAllRecipes().execute();
recycler = (RecyclerView) findViewById(R.id.recycler);
recycler.setHasFixedSize(true);
lManager = new LinearLayoutManager(this);
recycler.setLayoutManager(lManager);
adapter = new RecipeAdapter(this, items);
recycler.setAdapter(adapter);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
findViewById(R.id.fab).setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, NewRecipe.class);
intent.putExtra("usersession", (String)uns);
startActivity(intent);
}
});
actionBar = getSupportActionBar();
actionBar.setHomeAsUpIndicator(R.drawable.ic_menu_white_24dp);
actionBar.setDisplayHomeAsUpEnabled(true);
drawerLayout = (DrawerLayout) findViewById(R.id.navigation_drawer_layout);
NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_view);
TextView usersession = (TextView) findViewById(R.id.navigation_view).findViewById(R.id.usernameSession);
usersession.setText(uns);
if (navigationView != null) {
setupNavigationDrawerContent(navigationView);
View header = (View) getLayoutInflater().inflate(R.layout.navigation_drawer_header, null);
usernamesessionTV.setText(uns);
}
setupNavigationDrawerContent(navigationView);
adapter.notifyDataSetChanged();
db = new SQLiteHandler(getApplicationContext());
session = new SessionManager(getApplicationContext());
if (!session.isLoggedIn()) {
logoutUser();
}
user = db.getUserDetails();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if(items != null) {
outState.putParcelableArrayList("ITEMS", items);
items = null;
}
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
if (items == null) {
items = savedInstanceState.getParcelableArrayList("ITEMS");
recycler.setAdapter(adapter);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
drawerLayout.openDrawer(GravityCompat.START);
return true;
}
return super.onOptionsItemSelected(item);
}
private void setupNavigationDrawerContent(NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.item_navigation_drawer_allrecipes:
menuItem.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
intent = new Intent(MainActivity.this, MainActivity.class);
intent.putExtra("usersession", (String)uns);
startActivity(intent);
return true;
case R.id.item_navigation_drawer_myrecipes:
menuItem.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
intent = new Intent(MainActivity.this, MyRecipes.class);
intent.putExtra("usersession", (String)uns);
startActivity(intent);
return true;
case R.id.item_navigation_drawer_logout:
menuItem.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
logoutUser();
return true;
}
return true;
}
});
}
public static Drawable LoadImageFromWebOperations(String url) {
try {
InputStream is = (InputStream) new URL(url).getContent();
Drawable d = Drawable.createFromStream(is, "src name");
return d;
} catch (Exception e) {
return null;
}
}
private void logoutUser() {
session.setLogin(false);
db.deleteUsers();
Intent intent = new Intent(MainActivity.this, LoginActivity.class);
startActivity(intent);
finish();
}
class LoadAllRecipes extends AsyncTask<String, String, String> {
/**
* Muestra Progress Dialog mientras carga.
*/
@Override
protected void onPreExecute() {
super.onPreExecute();
if (pDialog != null) {
pDialog = null;
}
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage(getResources().getString(R.string.loadingRecipes));
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* Obtiene todas las recetas desde una URL
*/
protected String doInBackground(String... args) {
// Construye los parámetros a enviar
List<NameValuePair> params = new ArrayList<NameValuePair>();
JSONArray recipes = new JSONArray();
// Obtiene un JSON string desde la URL
jParser = new JSONParser();
JSONObject json = jParser.makeHttpRequest(AppConfig.URL_GET_ALL_RECIPES, "GET", params);
Log.d("All recipes: ", json.toString());
try {
// Comprueba si devolvió SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// recetas encontradas
// Obtiene array de recetas
recipes = json.getJSONArray(TAG_RECIPES);
// recorre todas las recetas agregándolas al List
for (int i = 0; i < recipes.length(); i++) {
JSONObject c = recipes.getJSONObject(i);
items.add(new Recipe(c.getInt(TAG_RECIPE_ID), c.getString(TAG_PHOTO), c.getString(TAG_NAME), c.getString(TAG_USERNAME)));
}
pDialog.dismiss();
} else {
// no se han encontrado recetas
Intent i = new Intent(getApplicationContext(), NewRecipe.class);
// Cierra todas las activities previas
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
}
}
RecipeAdapter.java：
public class RecipeAdapter extends RecyclerView.Adapter<RecipeAdapter.RecipeViewHolder> {
private ArrayList<Recipe> items;
private static Context context;
public View view;
public static class RecipeViewHolder extends RecyclerView.ViewHolder {
public int recipe_id;
public ImageView image;
public TextView name;
public TextView userName;
//public TextView method;
public TextView username;
public Recipe currentItem;
public RecipeViewHolder(View v) {
super(v);
v.setOnClickListener(new View.OnClickListener() {
@Override public void onClick(View v) {
Intent intent = new Intent(context, RecipeActivity.class);
intent.putExtra("recipe_id", currentItem.getRecipe_id());
context.startActivity(intent);
}
});
image = (ImageView) v.findViewById(R.id.recipeImage);
name = (TextView) v.findViewById(R.id.recipeName);
//userName = (TextView) v.findViewById(R.id.userName);
//method = (TextView) v.findViewById(R.id.recipeMethod);
username = (TextView) v.findViewById(R.id.username);
}
/*@Override
public void onClick(AdapterViewCompat<?> parent, View view, int position, long id) {
Intent intent = new Intent(context, RecipeActivity.class);
context.startActivity(intent);
}*/
}
public RecipeAdapter(Context context, ArrayList<Recipe> items) {
this.context = context;
this.items = items;
}
private String[] mDataset;
public RecipeAdapter(String[] dataset) {
mDataset = dataset;
}
public interface OnItemClickListener {
public void onItemClick(View view , int position);
}
@Override
public RecipeViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recipe_card, viewGroup, false);
RecipeViewHolder vh = new RecipeViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(RecipeViewHolder viewHolder, int i) {
viewHolder.recipe_id = items.get(i).getRecipe_id();
//viewHolder.image.setImageResource(items.get(i).getImage());
new DownloadImageTask((ImageView) viewHolder.image).execute(items.get(i).getImage());
viewHolder.name.setText(items.get(i).getName());
viewHolder.username.setText(context.getResources().getString(R.string.userTag)+" "+String.valueOf(items.get(i).getUsername()));
viewHolder.currentItem = items.get(i);
}
private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView bmImage;
public DownloadImageTask(ImageView bmImage) {
this.bmImage = bmImage;
}
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap imageBM = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
imageBM = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return imageBM;
}
protected void onPostExecute(Bitmap result) {
bmImage.setImageBitmap(result);
}
}
@Override
public int getItemCount() {
return items.size();
}
}
Recipe.java:
public class Recipe implements Parcelable {
private int recipe_id;
private String image;
private String name;
private String username;
private String method;
public Recipe(int recipe_id, String imagen, String name, String username) {
this.recipe_id = recipe_id;
this.image = imagen;
this.name = name;
this.username = username;
this.method = method;
}
public int getRecipe_id() {
return recipe_id;
}
public String getName() {
return name;
}
public String getUsername() {
return username;
}
public String getMethod() {
return method;
}
public String getImage() {
return image;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel parcel, int i) {
parcel.writeString(name);
parcel.writeString(method);
parcel.writeString(username);
parcel.writeString(image);
}
}