我在显示Json数据方面遇到了麻烦。
我想获取数据并将其保存在数据库中，然后刷新数据，每24小时更新一次。
但是在我的代码中每次访问webservice以显示数据时，我想要的是24小时后要更新的数据库以及要从数据库显示的其余时间值。
代码：
public class Banking_Economics extends ListActivity implements
OnItemClickListener {
ProgressDialog pd;
ListView lv;
SQLiteDB db;
SQLiteDatabase sdb;
private static final String CurrentAffairs = "CurrentAffairs";
// url to make request
private static String url = "http://10.0.2.2:53159/WebSite5/Default2.aspx";
// JSON Node names
private static final String TAG_FILE_NAME = "tests";
private static final String TAG_MESSAGE = "message";
// private static final String TAG_STATUS = "status";
public final ArrayList<HashMap<String, String>> testList = new ArrayList<HashMap<String, String>>();;
public final ArrayList<String> result=new ArrayList<String>();;
// contacts JSONArray
JSONArray tests;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.banking_eco);
lv = (ListView) findViewById(android.R.id.list);
// db=new SQLiteDB(Banking_Economics.this);
sdb = openOrCreateDatabase("me1.db", MODE_PRIVATE, null);
/*
* Log.i("In BankingEconomics","creating table"); String sql=
* "create table CurrentAffairs(id integer primary key autoincrement, message varchar)"
* ; sdb.execSQL(sql); Log.i("In BankingEconomics","table created");
* Toast.makeText(this, "your table is created",
* Toast.LENGTH_LONG).show();
*/
/*
* sql="delete from Questions where aliasname=28"; db.execSQL(sql);
* Log.i("In BankingEconomics","Records deleted...");
*/
// db.close();
new Thread(new Runnable() {
@Override
public void run() {
try {
boolean connected = false;
ConnectivityManager connectivityManager = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo[] info = connectivityManager.getAllNetworkInfo();
if(connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED ||
connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED) {
//we are connected to a network
connected = true;
//Toast.makeText(Banking_Economics.this, "network connected", Toast.LENGTH_LONG).show();
json();
//disp();
}
else{
connected = false;
// Toast.makeText(Banking_Economics.this, "network not connected", Toast.LENGTH_LONG).show();
// disp();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
// stuff that updates ui
/**
* Updating parsed JSON data into ListView
* */
disp();
}
});
} catch (Exception ex) {
ex.printStackTrace();
}
}
}).start();
// new LoadList().execute();
// sdb.close();
}
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
// TODO Auto-generated method stub
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public void disp() {
try {
Cursor c;
// c=db.getAllData();
String sql = "select * from CurrentAffairs LIMIT 10";
c = sdb.rawQuery(sql, null);
if (c != null) {
// if (c.moveToNext()) {
while (c.moveToNext()) {
String message = c.getString(c.getColumnIndex("message"));
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key =>
// value
map.put(TAG_MESSAGE, message);
result.add(message);
}// while(c.moveToNext());
}
} catch (Exception e) {
// TODO: handle exception
Log.i("In Banking economics", "Error-" + e.toString());
e.printStackTrace();
}
//ListAdapter adapter = new SimpleAdapter(Banking_Economics.this, result,R.layout.list_item, new String[] { TAG_MESSAGE },new int[] { R.id.textView1 });
ListAdapter adapter=new ArrayAdapter<String>(this, R.layout.list_item,R.id.textView1, result);
setListAdapter(adapter);
// selecting single ListView item
lv = getListView();
// Launching new screen on Selecting Single ListItem
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String message = ((TextView) view.findViewById(R.id.textView1))
.getText().toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(), News.class);
in.putExtra(TAG_MESSAGE, message);
startActivity(in);
}
});
}
public void json(){
// Your implementation
// Hashmap for ListView
File file = new File ("CurrentAffairs");
Calendar calendar = Calendar.getInstance();
//System.out.println("Current time => " + c.getTime());
calendar.setTime(new Date());
calendar.add(Calendar.HOUR, +24);
long mSec = calendar.get(Calendar.MILLISECOND);
SimpleDateFormat df = new SimpleDateFormat("dd-MMM-yyyy");
//String formattedDate = df.format(calendar.getTime());
//Date z=df.parse(formattedDate);
//long date=file.lastModified();
if(file.exists()){
if(file.lastModified()+mSec>System.currentTimeMillis()){
final ArrayList<HashMap<String, String>> testList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
Jsonparse jParser = new Jsonparse();
Log.i("in Main activity", "Jsonparse object declared");
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
Log.i("in Main activity", "JSON object declared");
try {
// Getting Array of Contacts
tests = json.getJSONArray(TAG_FILE_NAME);
Log.i("in Main activity", "JSON array called");
// looping through All Contacts
for (int i = 0; i < tests.length(); i++) {
JSONObject c = tests.getJSONObject(i);
// Storing each json item in variable
String message = c.getString(TAG_MESSAGE);
Log.i("In run", "" + message);
// adding each record to database
// ContentValues content=new ContentValues();
// content.put(TAG_MESSAGE, message);
// db.insert(message);
Log.i("In run", "" + message);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_MESSAGE, message);
// adding HashList to ArrayList
testList.add(map);
// Log.i("In SingleMenuItem Activity","inserting values in Questions");
ContentValues content = new ContentValues();
content.put(TAG_MESSAGE, message);
Log.i("In SingleMenuItem Activity",
"inserted Ques_no");
sdb.insertOrThrow(CurrentAffairs, null, content);
// Log.i("In SingleMenuItem Activity","inserted values in Questions");
}
} catch (JSONException e) {
Log.i("In Main", "" + e.toString());
e.printStackTrace();
}
}else{}
}else{final ArrayList<HashMap<String, String>> testList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
Jsonparse jParser = new Jsonparse();
Log.i("in Main activity", "Jsonparse object declared");
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
Log.i("in Main activity", "JSON object declared");
try {
// Getting Array of Contacts
tests = json.getJSONArray(TAG_FILE_NAME);
Log.i("in Main activity", "JSON array called");
// looping through All Contacts
for (int i = 0; i < tests.length(); i++) {
JSONObject c = tests.getJSONObject(i);
// Storing each json item in variable
String message = c.getString(TAG_MESSAGE);
Log.i("In run", "" + message);
// adding each record to database
// ContentValues content=new ContentValues();
// content.put(TAG_MESSAGE, message);
// db.insert(message);
Log.i("In run", "" + message);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_MESSAGE, message);
// adding HashList to ArrayList
testList.add(map);
// Log.i("In SingleMenuItem Activity","inserting values in Questions");
ContentValues content = new ContentValues();
content.put(TAG_MESSAGE, message);
Log.i("In SingleMenuItem Activity",
"inserted Ques_no");
sdb.insertOrThrow(CurrentAffairs, null, content);
// Log.i("In SingleMenuItem Activity","inserted values in Questions");
}
} catch (JSONException e) {
Log.i("In Main", "" + e.toString());
e.printStackTrace();
}}
//getjson();
}
}
注意：我已经尝试过类似问题的解决方案，但它无效。
我尝试使用广播接收器和alarmManager但它仍然无法正常工作。我想要改变代码，以便它每天只调用一次json函数。
答案 0 :(得分：0)
最简单的方法是： -
1.从服务器获取数据，解析并存储在数据库中。
2。）24小时后触发查询以删除所有数据库。这可以使用广播接收器和报警管理器来完成。
3.。）每次访问应用程序时，检查天气数据库是否有任何数据。如果是，则显示来自数据库的数据，否则从服务器获取数据。
如果您需要上述各点的详细说明。问我
修改
Cursor cur = db.rawQuery("SELECT COUNT(*) FROM TAB", null);
if (cur != null ) {
cur.moveToFirst();
if (cur.getInt (0)> 0) {
// table has data . Show data from table
// eg. tv.setText(cur.getInt(0))
}
}
}
此外，为了更新数据库，如果数据库不为空，则使用广播接收器和激活更新查询，否则将创建查询。
答案 1 :(得分：0)
对代码所做的更改：
boolean connected = false;
ConnectivityManager connectivityManager = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo[] info = connectivityManager.getAllNetworkInfo();
if(connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED ||
connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED) {
//we are connected to a network
connected = true;
//Toast.makeText(Banking_Economics.this, "network connected", Toast.LENGTH_LONG).show();
//File file = new File ("CurrentAffairs");
Calendar calendar = Calendar.getInstance();
//System.out.println("Current time => " + c.getTime());
calendar.setTime(new Date());
calendar.add(Calendar.DAY_OF_MONTH, +1);
long mSec = calendar.getTimeInMillis();
Intent it=new Intent(Current_Affairs.this,MyReceiver.class);
pendingIntent=PendingIntent.getBroadcast(Current_Affairs.this, 0, it, 0);
AlarmManager alarmManager=(AlarmManager)getSystemService(ALARM_SERVICE);
alarmManager.set(AlarmManager.RTC, mSec, pendingIntent);
/*if(file.exists()){
if(file.lastModified()+mSec>System.currentTimeMillis()){
json();
//disp();
}else{
}
}else{
json();
//disp();
}*/
//disp();
}
else{
connected = false;
// Toast.makeText(Banking_Economics.this, "network not connected", Toast.LENGTH_LONG).show();
// disp();
}
BroadCastReceiver代码：
public class MyReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context arg0, Intent arg1) {
// TODO Auto-generated method stub
Current_Affairs ca=new Current_Affairs();
ca.json();
}
}
希望这有助于其他人。