能够使用不同的适配器和数据库名称读取/写入另一个 Activity 。尝试复制粘贴并进行相应编辑。但是，出现了一些错误，例如数据库锁定。
遭遇.java
package com.example.medilearner;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.medilearner.database.JSONParser;
import com.medilearner.database.encounterDbAdapter;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
public class EncounterActivity extends Activity {
ListView list;
TextView eid;
TextView eclerkship;
TextView ename;
TextView etype;
TextView erequiredattempts;
// DATABASE ADAPTOR
encounterDbAdapter patientDB;
Context myContext;
Button Btngetdata;
ArrayList<HashMap<String, String>> encouterlist = new ArrayList<HashMap<String, String>>();
//URL to get JSON Array
private static String url = URL;
//JSON Node Names
private static final String TAG_ENCOUNTERS = "encounters";
private static final String TAG_E_ID = "e_id";
private static final String TAG_E_CLERKSHIP = "clerkship";
private static final String TAG_E_NAME = "encounter_name";
private static final String TAG_E_TYPE = "type";
private static final String TAG_E_REQUIRED_ATTEMPTS = "required_attempts";
JSONArray android = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_encounter);
encouterlist = new ArrayList<HashMap<String, String>>();
new JSONParse().execute();
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
eid = (TextView)findViewById(R.id.eid);
eclerkship = (TextView)findViewById(R.id.eclerkship);
ename = (TextView)findViewById(R.id.ename);
etype = (TextView)findViewById(R.id.etype);
erequiredattempts = (TextView)findViewById(R.id.erequiredattempts);
pDialog = new ProgressDialog(EncounterActivity.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
// Getting JSON Array from URL
android = json.getJSONArray(TAG_ENCOUNTERS);
for(int i = 0; i < android.length(); i++){
JSONObject c = android.getJSONObject(i);
// Storing JSON item in a Variable
String eid = c.getString(TAG_E_ID);
String eclerkship = c.getString(TAG_E_CLERKSHIP);
String ename = c.getString(TAG_E_NAME);
String etype = c.getString(TAG_E_TYPE);
String erequiredattempts = c.getString(TAG_E_REQUIRED_ATTEMPTS);
// Opening of database
patientDB = new encounterDbAdapter(myContext);
patientDB.open();
// Adding value HashMap key => value
patientDB.close();
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_E_ID, eid);
map.put(TAG_E_CLERKSHIP, eclerkship);
map.put(TAG_E_NAME, ename);
map.put(TAG_E_TYPE, etype);
map.put(TAG_E_REQUIRED_ATTEMPTS, erequiredattempts);
encouterlist.add(map);
list=(ListView)findViewById(R.id.list);
ListAdapter adapter = new SimpleAdapter(EncounterActivity.this, encouterlist,
R.layout.list_v,
new String[] { TAG_E_ID, TAG_E_CLERKSHIP, TAG_E_NAME, TAG_E_TYPE, TAG_E_REQUIRED_ATTEMPTS }, new int[] {
R.id.eid, R.id.eclerkship, R.id.ename, R.id.etype, R.id.erequiredattempts});
list.setAdapter(adapter);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(EncounterActivity.this, "You Clicked at "+encouterlist.get(+position).get("type"), Toast.LENGTH_SHORT).show();
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
EncounterDbAdapter.java
package com.medilearner.database;
import java.util.ArrayList;
import java.util.Locale;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class encounterDbAdapter {
private static final String DATABASE_NAME = "encounter.db";
private static final String DATABASE_TABLE = "encounterDb";
private static final int DATABASE_VERSION = 2;
private SQLiteDatabase _db;
private final Context encounterContext;
public static final String KEY_ID = "_id";
public static final int COLUMN_KEY_ID = 0;
public static final String ENCOUNTER_ID = "entry_initial";
public static final int COLUMN_INITIAL_ID = 1;
public static final String CLERKSHIP = "entry_date";
public static final int COLUMN_DATE_ID = 2;
public static final String ENCOUNTER_NAME = "entry_sitelocation";
public static final int COLUMN_SITE_ID = 3;
public static final String TYPE = "entry_clinic";
public static final int COLUMN_WARD_ID = 4;
public static final String REQUIRED_ATTEMPTS = "entry_history";
public static final int COLUMN_HISTORY_ID = 5;
protected static final String DATABASE_CREATE = "create table "
+ DATABASE_TABLE + " (" + KEY_ID
+ " integer primary key autoincrement, " + ENCOUNTER_ID + " Text, "
+ CLERKSHIP + " text not null, " + ENCOUNTER_NAME + " Text, "
+ TYPE + " Text, " + REQUIRED_ATTEMPTS + " Text);";
private String encounterDBADAPTER_LOG_CAT = "MY_LOG";
private myencounterDBOpenHelper EncounterdbHelper;
public encounterDbAdapter(Context _context) {
this.encounterContext = _context;
EncounterdbHelper = new myencounterDBOpenHelper(encounterContext, DATABASE_NAME, null,
DATABASE_VERSION);
_db=EncounterdbHelper.getWritableDatabase();
}
public void close() {
this._db.close();
Log.w(encounterDBADAPTER_LOG_CAT, "DB closed");
}
public void open() throws SQLiteException {
try{
_db=EncounterdbHelper.getWritableDatabase();
Log.w(encounterDBADAPTER_LOG_CAT, "DB opened as writable database");
}catch(SQLiteException ex){
_db=EncounterdbHelper.getReadableDatabase();
Log.w(encounterDBADAPTER_LOG_CAT, "DB opened as readable database");
}
}
//insertion
public long insertEncounterEntry(String eID, String clerkship, String encounterName, String type, String requiredAttempts) {
//insert new task
ContentValues newEntryValues=new ContentValues();
newEntryValues.put(ENCOUNTER_ID,eID);
newEntryValues.put(CLERKSHIP,clerkship);
newEntryValues.put(ENCOUNTER_NAME,encounterName);
newEntryValues.put(TYPE,type);
newEntryValues.put(REQUIRED_ATTEMPTS,requiredAttempts);
//Insert the row
Log.w(encounterDBADAPTER_LOG_CAT, "Inserted EntryInitial="+eID+" EntryDateOfDiagnosis="+clerkship + "Inserted EntrySiteLocation="+encounterName + "Inserted EntryWardClinic="+type + "Inserted entryPerformedHistory="+requiredAttempts +"into table"+DATABASE_TABLE);
long Integer = _db.insert(DATABASE_TABLE, null, newEntryValues);
Log.w(encounterDBADAPTER_LOG_CAT, "ID:" + Integer);
return Integer;
}
//removal
public boolean removeEntry(long _rowIndex) {
if(_db.delete(DATABASE_TABLE, KEY_ID+"="+_rowIndex, null)<=0)
{
Log.w(encounterDBADAPTER_LOG_CAT,"Removing Entrying where id="+_rowIndex+"Failed");
return false;
}
Log.w(encounterDBADAPTER_LOG_CAT,"Removing Entrying where id="+_rowIndex+"Success");
return true;
}
//updating
public boolean updateEntry(long _rowIndex,String entryInitial, String entryDateOfDiagnosis, String entrySiteLocation, String entryWardClinic, String entryPerformedHistory, String entryPerformedPhysical ) {
return false;
}
//retrival
public Cursor retrieveAllPatientEntriesCursor()
{
Cursor localCursor=null;
try
{
//
localCursor = this._db.query("mediLearnerDb", null, null, null, null, null, null);
// localCursor = this._db.query("mediLearnerDb", new String[] { "entry_initial"}, null, null, null, null, null).getString(1);
// test = this._db.query("mediLearnerDb", new String[] { "entry_initial"}, null, null, null, null, null).getString(1);
}
catch (SQLException localSQLException)
{
Log.w(this.encounterDBADAPTER_LOG_CAT, "Retrieve fail! ");
}
// return null;
return localCursor;
}
public class myencounterDBOpenHelper extends SQLiteOpenHelper {
public myencounterDBOpenHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(DATABASE_CREATE);
Log.w(encounterDBADAPTER_LOG_CAT, "Helper : DB " + DATABASE_TABLE
+ " Created!!");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
} // End of myDBOpenHelper
private void filter(String paramString)
{
paramString.toLowerCase(Locale.getDefault());
}
}// End of myDBAdapter
日志猫
12-06 17:30:58.036: D/dalvikvm(14495): GC_FOR_ALLOC freed 16K, 11% free 12207K/13703K, paused 14ms, total 16ms
12-06 17:30:58.116: W/ResourceType(14495): Failure getting entry for 0x010802c1 (t=7 e=705) in package 0 (error -75)
12-06 17:30:58.161: W/ResourceType(14495): Failure getting entry for 0x010802c1 (t=7 e=705) in package 0 (error -75)
12-06 17:30:58.161: W/ResourceType(14495): Failure getting entry for 0x010802c1 (t=7 e=705) in package 0 (error -75)
12-06 17:30:58.166: D/dalvikvm(14495): GC_CONCURRENT freed 236K, 12% free 12860K/14471K, paused 12ms+18ms, total 45ms
12-06 17:30:58.196: E/SpannableStringBuilder(14495): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
12-06 17:30:58.196: E/SpannableStringBuilder(14495): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
12-06 17:30:59.041: D/AbsListView(14495): Get MotionRecognitionManager
12-06 17:30:59.061: W/ResourceType(14495): Failure getting entry for 0x010802c1 (t=7 e=705) in package 0 (error -75)
12-06 17:31:02.786: D/AndroidRuntime(14495): Shutting down VM
12-06 17:31:02.786: W/dalvikvm(14495): threadid=1: thread exiting with uncaught exception (group=0x41bc42a0)
12-06 17:31:02.786: E/AndroidRuntime(14495): FATAL EXCEPTION: main
12-06 17:31:02.786: E/AndroidRuntime(14495): java.lang.NullPointerException
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
12-06 17:31:02.786: E/AndroidRuntime(14495): at com.medilearner.database.encounterDbAdapter.<init>(encounterDbAdapter.java:57)
12-06 17:31:02.786: E/AndroidRuntime(14495): at com.example.medilearner.EncounterActivity$JSONParse.onPostExecute(EncounterActivity.java:123)
12-06 17:31:02.786: E/AndroidRuntime(14495): at com.example.medilearner.EncounterActivity$JSONParse.onPostExecute(EncounterActivity.java:1)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.os.AsyncTask.finish(AsyncTask.java:631)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.os.AsyncTask.access$600(AsyncTask.java:177)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.os.Handler.dispatchMessage(Handler.java:99)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.os.Looper.loop(Looper.java:137)
12-06 17:31:02.786: E/AndroidRuntime(14495): at android.app.ActivityThread.main(ActivityThread.java:4921)
12-06 17:31:02.786: E/AndroidRuntime(14495): at java.lang.reflect.Method.invokeNative(Native Method)
12-06 17:31:02.786: E/AndroidRuntime(14495): at java.lang.reflect.Method.invoke(Method.java:511)
12-06 17:31:02.786: E/AndroidRuntime(14495): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
12-06 17:31:02.786: E/AndroidRuntime(14495): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
12-06 17:31:02.786: E/AndroidRuntime(14495): at dalvik.system.NativeStart.main(Native Method)
最佳答案
我猜你的上下文是空的。
这里:patentDB = new meetDbAdapter(myContext);
解决方案:patentDB = new meetDbAdapter(EncounterActivity.this);
希望这有帮助。
关于java - 空异常。数据库已锁定，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20420414/