我已经在 listview
中解析了 JSON 数据,现在我想让它离线可用。
有没有办法把JSON数据保存在手机里,这样手机离线的时候也能看到数据?
有人知道例子吗?
现在可以编辑了:
public class MainActivity extends ListActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new TheTask().execute();
}
class TheTask extends AsyncTask<Void, Void, JSONArray> {
InputStream is = null;
String result = "";
JSONArray jArray = null;
ProgressDialog pd;
@Override
protected void onPostExecute(JSONArray result) {
super.onPostExecute(result);
pd.dismiss();
ArrayList<String> list= new ArrayList<String>();
try {
for(int i=0;i<result.length();i++) {
JSONObject jb = result.getJSONObject(i) ;
String name = jb.getString("name")+" "+jb.getString("Art");
list.add(name);
}
} catch(Exception e) {
e.printStackTrace();
}
setListAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, list));
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = ProgressDialog.show(MainActivity.this, "State",
"Loading...", true);
}
@Override
protected JSONArray doInBackground(Void... arg0) {
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("***");
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
// Convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
writeToFile(result);
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
try {
jArray = new JSONArray(result);
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
try {
jArray = new JSONArray(readFromFile());
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
return jArray;
}
}
private void writeToFile(String data) {
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("config.txt", Context.MODE_PRIVATE));
outputStreamWriter.write(data);
outputStreamWriter.close();
}
catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
private String readFromFile() {
String ret = "";
try {
InputStream inputStream = openFileInput("config.txt");
if ( inputStream != null ) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String receiveString = "";
StringBuilder stringBuilder = new StringBuilder();
while ( (receiveString = bufferedReader.readLine()) != null ) {
stringBuilder.append(receiveString);
}
inputStream.close();
ret = stringBuilder.toString();
}
} catch (FileNotFoundException e) {
Log.e("login activity", "File not found: " + e.toString());
} catch (IOException e) {
Log.e("login activity", "Can not read file: " + e.toString());
}
return ret;
}
}
最佳答案
你有两种方法。您要么创建一个数据库并将所有数据保存在那里,然后在需要时将其取回。或者你手上的数据不多,不想和数据库打交道,那你就把json串写到内存卡里的一个文本文件里,等你离线的时候再读。
对于第二种情况,每次上网时,您都可以从您的网络服务中检索相同的 json,并将其覆盖到旧的。通过这种方式,您可以确保将最新的 json 保存到设备。
关于java - 如何缓存 Json 数据以供离线使用?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21460461/