我一直在开发一个应用程序，该应用程序使用Sugar ORM将数据存储在本地sqlite数据库中，并将其也发布到listview中，因此我的任务是从Internet连接为json时直接来自json的直接数据发布listview可用，但是如果连接不可用，那么我必须在数据库中检索已经保存的数据并在列表视图中填充，我已经能够下载并保存数据，但是当网络不可用时，我必须在内部检索它getdatafromlocal方法没有发生
MainActivity.java文件
public class MainActivity extends AppCompatActivity {
private List<Movie> movieList;
private RecyclerView.Adapter adapter;
JSONObject jsonObject;
List<Note> note;
CursorAdapter c;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RecyclerView mList = findViewById(R.id.main_list);
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);
// getData();
if (isNetworkAvailable()) {
getData();
}
else
{
getDataFromLocal();
Toast.makeText(getApplicationContext(),"no internet",Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(),"populating from local data",Toast.LENGTH_SHORT).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 < 20; i++) {
try {
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");
note = new ArrayList<>();
note.add(new Note(Title,Image,Album,Thumbnail));
SugarRecord.saveInTx(note);
note.size();
copydatabase();
Toast.makeText(getApplicationContext(), "Rows Inserted
into local storage too", Toast.LENGTH_SHORT).show();
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);
} catch (JSONException e) {
e.printStackTrace();
progressDialog.dismiss();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
copydatabase();
} catch (IOException e) {
e.printStackTrace();
}
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 void getDataFromLocal() {
//what to do next
}
public void copydatabase() throws IOException {
//File actualFile = null;
File actualFile= new File(new
SugarDb(MainActivity.this).getDB().getPath()); //actual file
File curentfile = new File(actualFile.toString()); //new file generated
Log.e("actualPath", actualFile.toString());
File newFile = createTempFile("SugarImagesList",".db",
Environment.getExternalStorageDirectory());
newFile.mkdirs();
if(!newFile.mkdirs()){
Toast.makeText(MainActivity.this, "file exists",
Toast.LENGTH_SHORT).show();
}
Log.e("newPath", newFile.toString());
boolean yes= FileUtils.copyFile(curentfile,newFile);
if(yes) {
Log.e("result", "" + true);
Toast.makeText(getApplicationContext(), "Database Copied to SD card",
Toast.LENGTH_SHORT).show();
}
}
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager
= (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = null;
if (connectivityManager != null) {
activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
}
return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}
}
Movie.java文件
public class Movie {
public String title;
public String albumid;
public String thumbnailurl;
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 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, String albumid, String
thumbnailurl ) {
this.title = title;
this.image = image;
this.id = id;
this.albumid = albumid;
this.thumbnailurl = thumbnailurl;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
Note.java文件
public class Note extends SugarRecord {
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;
String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
private String image;
public Note(String title ,String image,String albumid, String thumbnailurl)
{
this.title = title;
this.image = image;
this.albumid = albumid;
this.thumbnailurl = thumbnailurl;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
MovieAdapter.java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();
}
}
}
}
答案 0 :(得分：0)
After few trials and errors , i have been able to retrieve the data which was stored in the local database through Sugar ORM, I changed my MainActivity a bit to get the desired results
public class MainActivity extends AppCompatActivity {
EditText firstname;
EditText lastname;
Button button;
Note note;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
firstname=findViewById(R.id.edit1);
lastname=findViewById(R.id.edit2);
button=findViewById(R.id.button);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
return id == R.id.action_settings || super.onOptionsItemSelected(item);
}
public void click(View view) {
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 <1 ; i++) {
try {
JSONObject jsonObject;
jsonObject = response.getJSONObject(i);
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.i("title",Title);
Log.i("album",Album);
Toast.makeText(getApplicationContext(), Title, Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(), Album, Toast.LENGTH_SHORT).show();
note = new Note(Title, Album);
note.save();
// copydatabase();
// Toast.makeText(getApplicationContext(), "Rows Inserted into local storage too", Toast.LENGTH_SHORT).show();
progressDialog.dismiss();
} catch (JSONException e) {
e.printStackTrace();
progressDialog.dismiss();
}
}
/* try {
copydatabase();
} catch (IOException e) {
e.printStackTrace();
}*/
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e("Volley", error.toString());
progressDialog.dismiss();
}
});
RequestQueue requestQueue = Volley.newRequestQueue(this);
requestQueue.add(jsonArrayRequest);
}
public void show(View view) {
String myTitle = note.getTitle();
String myAlbumid=note.getAlbumId();
Log.e("title",myTitle);
Log.e("album",myAlbumid);
}
public void deletedatabase(View view) {
boolean check= MainActivity.this.deleteDatabase("notes.db");
if(check){
Toast.makeText(getApplicationContext(),"database deleted",Toast.LENGTH_SHORT).show();
}
}
public void copydatabase(View view) throws IOException {
File actualFile = null;
actualFile= new File(new SugarDb(MainActivity.this).getDB().getPath()); //actual file
File curentfile = new File(actualFile.toString()); //new file generated
Log.e("actualPath", actualFile.toString());
File newFile = createTempFile("NewSugarAppFiles",".db",Environment.getExternalStorageDirectory());
Log.e("newPath", newFile.toString());
boolean yes=FileUtils.copyFile(curentfile,newFile);
if(yes) {
Log.e("result", "" + true);
Toast.makeText(getApplicationContext(), "Database Copied to SD card", Toast.LENGTH_SHORT).show();
}
}
}
Here click method would call an API and store the data in the local database and show method would retrieve the stored data.Other classes remain same, I have dropped Recyclerview to simplify things but the data can be stored and retrieved from the Recyclerview also in the same manner as written above.