我想在我的应用程序中添加一项功能，以确保如果用户连接到互联网甚至一次，那么从Firebase解析的信息（在这种情况下，每个对象有3个字符串变量的ArrayList对象）可以以某种方式保存（使用sharedPreferences或文件或任何其他方法），以便下次用户在没有互联网连接的情况下打开应用程序，然后应显示此已经解析的数据，如果有互联网连接，则它应该正常工作。
为此，我开始了解磁盘持久性，但它无法正常工作。这是我的代码
package in.protechlabz.www.yavatmalindicatorserver;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.client.ValueEventListener;
import com.google.android.gms.ads.AdView;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.storage.StorageReference;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Nikesh on 23/12/2016.
*/
public class ContactListActivity extends AppCompatActivity {
private List<ContactData> generalList = new ArrayList<ContactData>();
Intent intent;
private int listItemSelector=0; // This variable will be used to store information obtained from
// intent regarding which listview to be loaded
private AdView mAdView2;
Firebase myFirebaseRef;
private ArrayAdapter<ContactData> listItemAdapter;
private StorageReference mStorageRef;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.directory_list);
/* Admob related important code*/
mAdView2 = (AdView) findViewById(R.id.adView2);
com.google.android.gms.ads.AdRequest adRequest = new com.google.android.gms.ads.AdRequest.Builder().build();
mAdView2.loadAd(adRequest);
Firebase.setAndroidContext(this);
// Extract information from intent for listItemSelector
Bundle extras = getIntent().getExtras();
if(extras != null) {
listItemSelector = extras.getInt("ListPosition");
}
//if(isNetworkAvailable()) {
final ProgressDialog dialog = new ProgressDialog(ContactListActivity.this);
dialog.setMessage("Loading Data...");
dialog.setCanceledOnTouchOutside(false);
dialog.show();
//Adding information to individual lists
/*Firebase related code*/
myFirebaseRef = new Firebase("https://yavatmalindicatorserver.firebaseio.com");
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
myFirebaseRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
generalList.clear();
switch (listItemSelector) {
case 1:
for (DataSnapshot eachContact : snapshot.child("Hotels and Lodges").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 2:
for (DataSnapshot eachContact : snapshot.child("Banks").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 3:
for (DataSnapshot eachContact : snapshot.child("Tours and Travels").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 4:
for (DataSnapshot eachContact : snapshot.child("Function Halls").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 5:
for (DataSnapshot eachContact : snapshot.child("Hospitals").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 6:
for (DataSnapshot eachContact : snapshot.child("Educational Institutes").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 7:
for (DataSnapshot eachContact : snapshot.child("Medicals").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 8:
for (DataSnapshot eachContact : snapshot.child("Government Offices").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 9:
for (DataSnapshot eachContact : snapshot.child("Press").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 10:
for (DataSnapshot eachContact : snapshot.child("Railways (Dhamangaon)").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
// From here emergency list
case 11:
for (DataSnapshot eachContact : snapshot.child("Police Station").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 12:
for (DataSnapshot eachContact : snapshot.child("Fire Brigade").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 13:
for (DataSnapshot eachContact : snapshot.child("Ambulance").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 14:
for (DataSnapshot eachContact : snapshot.child("Blood Banks").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
case 15:
for (DataSnapshot eachContact : snapshot.child("Snake Friends").getChildren()) {
ContactData tempData = eachContact.getValue(ContactData.class);
generalList.add(tempData);
}
break;
}
listItemAdapter.notifyDataSetChanged();
dialog.hide();
}
@Override
public void onCancelled(FirebaseError error) {
}
});
//}else {
// Toast.makeText(this, "Sorry No Internet Connection",
// Toast.LENGTH_SHORT).show();
//finish();
//}
listItemAdapter = new ContactDataAdapter(this,R.layout.eachcontact_row,generalList);
ListView myContactList = (ListView) findViewById(R.id.directoryList);
//For card view
myContactList.addHeaderView(new View(this));
myContactList.addFooterView(new View(this));
myContactList.setAdapter(listItemAdapter);
myContactList.setOnItemClickListener(
new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
ContactData singleItem = (ContactData) parent.getItemAtPosition(position);
String number = singleItem.getTelephone();
// Parse only one number if multiple numbers present
int indexOfComma = number.indexOf(",");
if(indexOfComma != -1) {
number = number.substring(0,indexOfComma);
}
intent = new Intent(Intent.ACTION_DIAL);
intent.setData(Uri.parse("tel:" + number));
startActivity(intent);
}
}
);
}
/*public boolean isNetworkAvailable(final Context context) {
final ConnectivityManager connectivityManager = ((ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE));
return connectivityManager.getActiveNetworkInfo() != null && connectivityManager.getActiveNetworkInfo().isConnected();
}*/
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager
= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}
}
请帮忙。
答案 0 :(得分：1)
为此目的，有一个简单但非常方便的库。它被称为TinyDB。将其添加到项目后，您只需在TinyDB实例上调用putListObject()即可保存数据。
祝你好运