如何存储JSON SQLite中 [英] How to store JSON in SQLite
本文介绍了如何存储JSON SQLite中的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有存储JSON数据sqlite的问题。这是code，我想实现现在。 JSON数据不是特别大，只有40它行。
I am having issues with storing JSON data to sqlite. This is the code which I am trying to implement right now. The JSON data is not particularly big with only 40 lines in it.
主要活动是：
public class DatabaseActivity extends Activity {
/** Called when the activity is first created. */
public DBAdapter
DBAdapter =new DBAdapter(this);
TextView txt;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create a crude view - this should really be set via the layout resources
// but since its an example saves declaring them in the XML.
LinearLayout rootLayout = new LinearLayout(getApplicationContext());
txt = new TextView(getApplicationContext());
rootLayout.addView(txt);
setContentView(rootLayout);
// Set the text and call the connect function.
txt.setText("Connecting...");
//call the method to run the data retreival
txt.setText(getServerData(KEY_13));
}
public static final String KEY_13 = "http://xxx.xxx.xxx/api/train.php";
private String getServerData(String returnString) {
InputStream is = null;
String result = "";
//the train line to send
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("code","A"));
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_13);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
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();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
//parse json data
try{
JSONArray jArray = new JSONArray(result);
for(int i=0;i<jArray.length();i++){
JSONObject json_data = jArray.getJSONObject(i);
DBAdapter.insertTrain(json_data.getString("id"),
json_data.getString("code"),
json_data.getString("station"),
json_data.getString("platform"),
json_data.getString("timetillstation"),
json_data.getString("traindestination"),
//Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return returnString;
}
}
该适配器：
public class DBAdapter{
public static final String KEY_ID = "id";
public static final String KEY_Code = "code";
public static final String KEY_Station = "station";
public static final String KEY_Platform = "platform";
public static final String KEY_TimeTillStation = "timetillstation";
public static final String KEY_TrainDestination = "traindestination";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "trains";
private static final String DATABASE_TABLE = "Mekerel";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table titles (id integer primary key, "
+ "code text not null,"
+ "station text not null,"
+ "platform text not null,"
+ "timetillstation text not null,"
+ "traindestination text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
this.db=DBHelper.getWritableDatabase();
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE); }
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS titles");
onCreate(db);
}
}
//---opens the database---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a train into the database---
public long insertTrain(String id, String code, String station, String platform, String timetillstation, String traindestination)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_ID, id);
initialValues.put(KEY_Code, code);
initialValues.put(KEY_Station, station);
initialValues.put(KEY_Platform, platform);
initialValues.put(KEY_TimeTillStation, timetillstation);
initialValues.put(KEY_TrainDestination, traindestination);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---retrieves all the ttrain---
public Cursor getAllTrains()
{
return db.query(DATABASE_TABLE, new String[] {
KEY_ID,
KEY_Code,
KEY_Station,
KEY_Platform,
KEY_TimeTillStation,
KEY_TrainDestination},
null,
null,
null,
null,
null,
null);
}
//---retrieves a particular train---
public Cursor getTrain(long id) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {
KEY_ID,
KEY_Code,
KEY_Station,
KEY_Platform,
KEY_TimeTillStation,
KEY_TrainDestination},
KEY_ID + "=" + id,
null,
null,
null,
null,
null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---updates a train---
public boolean updateTrain(long id, String code, String station, String platform, String timetillstation, String traindestination)
{
ContentValues args = new ContentValues();
args.put(KEY_Code, code);
args.put(KEY_Station, station);
args.put(KEY_Platform, platform);
args.put(KEY_TimeTillStation, timetillstation);
args.put(KEY_TrainDestination, traindestination);
return db.update(DATABASE_TABLE, args,
KEY_ID + "=" + id, null) > 0;
}
}
我不知道从哪里何去何从如仍有问题。日志猫显示以下内容：
I am not sure where to go from here as there are still issues. The log cat displays the following:
12-04 12:43:09.691: E/AndroidRuntime(21334): FATAL EXCEPTION: main
12-04 12:43:09.691: E/AndroidRuntime(21334): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{ta.dabase/ta.dabase.DatabaseActivity}: java.lang.NullPointerException
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1680)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.access$1500(ActivityThread.java:123)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.os.Handler.dispatchMessage(Handler.java:99)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.os.Looper.loop(Looper.java:130)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.main(ActivityThread.java:3835)
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.reflect.Method.invokeNative(Native Method)
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.reflect.Method.invoke(Method.java:507)
12-04 12:43:09.691: E/AndroidRuntime(21334): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
12-04 12:43:09.691: E/AndroidRuntime(21334): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
12-04 12:43:09.691: E/AndroidRuntime(21334): at dalvik.system.NativeStart.main(Native Method)
12-04 12:43:09.691: E/AndroidRuntime(21334): Caused by: java.lang.NullPointerException
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:118)
12-04 12:43:09.691: E/AndroidRuntime(21334): at ta.dabase.DBAdapter.<init>(DBAdapter.java:43)
12-04 12:43:09.691: E/AndroidRuntime(21334): at ta.dabase.DatabaseActivity.<init>(DatabaseActivity.java:32)
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.Class.newInstanceImpl(Native Method)
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.Class.newInstance(Class.java:1409)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1672)
12-04 12:43:09.691: E/AndroidRuntime(21334): ... 11 more
最后，我想知道是否有人可以帮助我调试从某种意义上讲什么，在哪里放置相应的日志记录code所以检测，其中code会错到底是什么？ 谢谢
Finally, I was wondering if anyone could help me with debugging in a sense what and where to place appropriate logging code so to detect where code is going wrong exactly? Thanks
推荐答案
要解决这个问题，必须遵循这个步骤
To solve this problem you must follow this steps
1）创建其中包含的属性按你的JSON数据的类。
1) Create the class which contains properties as per your json data.
2）反序列化JSON数据到您的类。 （ JSON与类映射）
2) Deserialize your json data into your class. ( Mapping of json with class)
3）存储在类的所有属性的值放入数据库中（ sqllite 的）（类与数据库映射）
3) Store the values of all properties in that class into database(sqllite) (Mapping of class with database )
4） ****保存您的工作***！
4) ****Save your work*** !
完成！享受Jsoning !!
Done ! Enjoy Jsoning !!
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