我想问一下，如何在我的Android应用程序中填充来自SQLite数据库的recyclerview。实际上，数据来自远程服务器通过json，我的任务是填充recyclerview，当Internet可用时填充API调用，如果它不可用，那么我必须将该远程服务器响应保存到本地SQLite数据库，以便我可以获取保存的结果，并在没有互联网的情况下填充列表
public class SQLiteHandler extends SQLiteOpenHelper {
private static final String TAG = SQLiteHandler.class.getSimpleName();
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "image_api";
// Login table name
private static final String TABLE_LIST = "images";
// Login Table Columns names
public static final String KEY_ID = "id";
public static final String KEY_TITLE = "title";
public static final String KEY_ALBUMID = "albumid";
public static final String KEY_THUMBNAILURL = "thumbnailurl";
public static final String KEY_IMAGE = "image";
SQLiteHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_LIST + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_TITLE + " TEXT,"
+ KEY_ALBUMID + " TEXT UNIQUE," + KEY_THUMBNAILURL + " TEXT,"
+ KEY_IMAGE + " TEXT" + ")";
db.execSQL(CREATE_LOGIN_TABLE);
Log.d(TAG, "Database tables created");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LIST);
// Create tables again
onCreate(db);
}
/**
* Storing user details in database
* */
void addUser(String Id, String title, String albumid, String thumbnailurl, String image) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_ID, Id); // Name
values.put(KEY_TITLE, title); // Email
values.put(KEY_ALBUMID, albumid); // Email
values.put(KEY_THUMBNAILURL, thumbnailurl);
values.put(KEY_IMAGE, image);// Created At
// Inserting Row
long id = db.insert(TABLE_LIST, null, values);
db.close(); // Closing database connection
Log.d(TAG, "New user inserted into sqlite: " + id);
}
/**
* Getting user data from database
* */
public HashMap<String, String> getUserDetails() {
HashMap<String, String> user = new HashMap<String, String>();
String selectQuery = "SELECT * FROM " + TABLE_LIST;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// Move to first row
cursor.moveToFirst();
if (cursor.getCount() > 0) {
user.put("Id", cursor.getString(1));
user.put("title", cursor.getString(2));
user.put("albumid", cursor.getString(3));
user.put("thumbnailurl", cursor.getString(4));
user.put("image", cursor.getString(5));
}
cursor.close();
db.close();
// return user
Log.d(TAG, "Fetching user from Sqlite: " + user.toString());
return user;
}
long getProfilesCount() {
SQLiteDatabase db = this.getReadableDatabase();
long count = DatabaseUtils.queryNumEntries(db, TABLE_LIST);
db.close();
return count;
}
public Cursor getAllPersons() {
SQLiteDatabase db = this.getReadableDatabase();
return db.rawQuery( "SELECT * FROM " + TABLE_LIST, null );
}
}
这是我的mainActivity
public class MainActivity extends AppCompatActivity {
private List<Movie> movieList;
private RecyclerView.Adapter adapter;
private SQLiteHandler db;
long profile_counts;
//private ArrayList noList;
@Override
protected void onDestroy() {
super.onDestroy();
if (db != null)
db.close();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RecyclerView mList = findViewById(R.id.main_list);
db = new SQLiteHandler(getApplicationContext());
profile_counts = db.getProfilesCount();
movieList = new ArrayList<>();
adapter = new MovieAdapter(getApplicationContext(), movieList);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(mList.getContext(), linearLayoutManager.getOrientation());
mList.setHasFixedSize(true);
mList.setLayoutManager(linearLayoutManager);
mList.addItemDecoration(dividerItemDecoration);
mList.setAdapter(adapter);
if (isNetworkAvailable()) {
getData();
}
else
{
Toast.makeText(MainActivity.this,"No Internet",Toast.LENGTH_LONG).show();
}
}
private void getData() {
final ProgressDialog progressDialog = new ProgressDialog(this);
progressDialog.setMax(100);
progressDialog.setMessage("Its loading....");
progressDialog.setTitle("Imageview Example");
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.show();
String url = "http://jsonplaceholder.typicode.com/photos";
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(url, new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
for (int i = 0; i < response.length(); i++) {
try {
JSONObject jsonObject = response.getJSONObject(i);
Movie movie = new Movie();
movie.setTitle(jsonObject.getString("title"));
movie.setId(jsonObject.getInt("id"));
movie.setImage(jsonObject.getString("url"));
movie.setAlbumid(jsonObject.getString("albumId"));
movie.setThumbnailurl(jsonObject.getString("thumbnailUrl"));
movieList.add(movie);
String Title = jsonObject.getString("title");
String Id = jsonObject.getString("id");
String Image = jsonObject.getString("url");
String Album = jsonObject.getString("albumId");
String Thumbnail = jsonObject.getString("thumbnailUrl");
Log.e("List Loaded", "imagesList");
Log.i("Title", Title);
Log.i("Id", Id);
Log.i("Image", Image);
Log.i("Album", Album);
Log.i("Thumbnail", Thumbnail);
db.addUser(Id, Title, Album, Thumbnail, Image);
Log.d("number of elements", String.valueOf(profile_counts));
} catch (JSONException e) {
e.printStackTrace();
progressDialog.dismiss();
}
}
adapter.notifyDataSetChanged();
progressDialog.dismiss();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e("Volley", error.toString());
progressDialog.dismiss();
}
});
RequestQueue requestQueue = Volley.newRequestQueue(this);
requestQueue.add(jsonArrayRequest);
}
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager
= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = null;
if (connectivityManager != null) {
activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
}
return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}
}
现在我只想知道如何从SQLite数据库填充recyclerview，到目前为止我已经能够从远程服务器获取数据并在SqliteHandler类的帮助下将其保存在SQLite数据库中。这是我的适配器类
public class MovieAdapter extends RecyclerView.Adapter<MovieAdapter.ViewHolder> {
private Context context;
private List<Movie> list;
private String link;
private imageDownload image;
MovieAdapter(Context context, List<Movie> list) {
this.context = context;
this.list = list;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(context).inflate(R.layout.list, parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull final MovieAdapter.ViewHolder holder, int position) {
Movie movie = list.get(position);
holder.textTitle.setText(movie.getTitle());
holder.textId.setText(String.valueOf(movie.getId()));
holder.textThumb.setText(movie.getThumbnailurl());
holder.textAlbum.setText(String.valueOf(movie.getAlbumid()));
Picasso.with(context).load(movie.getImage())
.into(holder.photo);
holder.photo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
link = list.get(holder.getAdapterPosition()+1).getImage();
image = new imageDownload(context, holder.photo);
image.execute(link);
Log.e("image link", link);
Toast.makeText(context, "image clicked: " + holder.getAdapterPosition(), Toast.LENGTH_LONG).show();
}
});
}
@Override
public int getItemCount() {
return list.size();
}
class ViewHolder extends RecyclerView.ViewHolder {
TextView textTitle, textId, textThumb, textAlbum;
ImageView photo;
ViewHolder(View itemView) {
super(itemView);
textTitle = itemView.findViewById(R.id.title_1);
textId = itemView.findViewById(R.id.id_1);
textThumb = itemView.findViewById(R.id.thumbnailurl_1);
textAlbum = itemView.findViewById(R.id.albumid_1);
photo = itemView.findViewById(R.id.imageview);
}
}
class imageDownload extends AsyncTask<String, Integer, Bitmap> {
Context context;
ImageView imageView;
Bitmap bitmap;
InputStream in = null;
//constructor.
imageDownload(Context context, ImageView imageView) {
this.context = context;
this.imageView = imageView;
}
@Override
protected void onPreExecute() {
}
@Override
protected Bitmap doInBackground(String... params) {
HttpURLConnection httpURLConnection = null;
try {
URL url = new URL(params[0]);
httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.connect();
in = httpURLConnection.getInputStream();
BufferedInputStream bufferedInputStream = new
BufferedInputStream(in);
bitmap = BitmapFactory.decodeStream(in);
in.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (httpURLConnection != null) {
httpURLConnection.disconnect();
}
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap data) {
imageView.setImageBitmap(data);
try {
try {
saveImage(data);
} catch (MalformedURLException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
// System.out.print(Log.e("Image Data",data.toString()));
}
private void saveImage(Bitmap data) throws FileNotFoundException, MalformedURLException {
File createFolder = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "test");
File saveImage = new File(createFolder, "downloadedImage.jpg");
try {
OutputStream outputStream = new FileOutputStream(saveImage);
data.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);
outputStream.flush();
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Movie.class
public class Movie {
public String title;
public String getAlbumid() {
return albumid;
}
public void setAlbumid(String albumid) {
this.albumid = albumid;
}
public String getThumbnailurl() {
return thumbnailurl;
}
public void setThumbnailurl(String thumbnailurl) {
this.thumbnailurl = thumbnailurl;
}
public String albumid;
public String thumbnailurl;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
private int id;
private String image;
public Movie() {
}
public Movie(String title, String image, int id) {
this.title = title;
this.image = image;
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
答案 0 :(得分：2)
以下代码是从Sqlite DB获取数据并在Recycler视图中显示数据的简单示例
private List<Movie> movieList;
private RecyclerView mRecyclerView;
private MovieAdapter adapter;
private SQLiteHandler db;
Cursor cursor = db.getUserDetails();
if (cursor.moveToFirst()) {
do {
movieList.add(new Movie(
cursor.getInt(0),
cursor.getString(1),
cursor.getString(2),
cursor.getString(3),
cursor.getDouble(4)
));
} while (cursor.moveToNext());
MovieAdapter adapter = new MovieAdapter(this, movieList);
mRecyclerView.setAdapter(adapter);
}