I'm getting a problem when I launch my App. I get this issue, Attempt to invoke a virtual method on a null object reference. I think its Because I didn't create the instance of LoadJobList Correctly but I'm not entirely sure.
Main Activity [EDITED]
public class MainActivity extends AppCompatActivity {
IntDataBaseHelper intDataBaseHelper;
ArrayAdapter<String> mAdapter;
ListView lstJob;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.header);
/// create instance of db helper and jobs
IntDataBaseHelper myhelper = new IntDataBaseHelper(this);
lstJob = (ListView)findViewById(R.id.lstJob);
LoadJobList();
// Create the database (only if it doesn't exists)
// does so by copying from the assets
if (CopyDBFromAssets.createDataBase(this,IntDataBaseHelper.DB_NAME)) {
// Get the data from the database
ArrayList<String> jobs = intDataBaseHelper.getJobList();
for (String s : jobs) {
Log.d("JobList", "Found Job " + s);
}
} else {
throw new RuntimeException("No Usable Database exists or was copied from the assets.");
}
}
// loads job to screen
private void LoadJobList() {
ArrayList<String> Joblist = intDataBaseHelper.getJobList();
if (mAdapter == null) {
mAdapter = new ArrayAdapter<String>(this,R.layout.header,R.id.header);
mAdapter = new ArrayAdapter<>(this,R.layout.row,R.id.BtnComplete);
mAdapter = new ArrayAdapter<>(this, R.layout.row, R.id.Job_name,Joblist);
lstJob.setAdapter(mAdapter);
} else {
mAdapter.clear();
mAdapter.addAll(Joblist);
mAdapter.notifyDataSetChanged();
}
}
public void JobComplete(View view){
View parent = (View)view.getParent();
TextView taskTextView=(TextView)parent.findViewById(R.id.BtnComplete);
Log.e("String",(String) taskTextView.getText());
}
}
LogCat
[ 10-30 07:24:10.779 1506: 1551 D/]
HostConnection::get() New Host Connection established 0x949247c0, tid 1551
10-30 07:24:11.120 2774-2774/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.joelg.clapp, PID: 2774
java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.example.joelg.clapp/com.example.joelg.clapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.ArrayList com.example.joelg.clapp.IntDataBaseHelper.getJobList()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.ArrayList com.example.joelg.clapp.IntDataBaseHelper.getJobList()' on a null object reference
at com.example.joelg.clapp.MainActivity.LoadJobList(MainActivity.java:52)
at com.example.joelg.clapp.MainActivity.onCreate(MainActivity.java:31)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
getJobList method
public ArrayList<String> getJobList() {
ArrayList<String> JobList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(DB_TABLE,new String[]
{DB_COLUMN},null,null,null,null,null);
while(cursor.moveToNext()){
int index = cursor.getColumnIndex(DB_COLUMN);
JobList.add(cursor.getString(index));
}
cursor.close();
db.close();
return JobList;
}
DB helper class
package com.example.joelg.clapp;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
/**
* Created by joelg on 22/10/2017.
*/
public class IntDataBaseHelper extends SQLiteOpenHelper{
public static String DB_PATH ="//data/data/com.example.joelg.clapp/databases";
public static final String DB_NAME = "JobList";
private static final String DB_COLUMN = "jobNM";
private static final String DB_TABLE = "job";
public static final String DB_JOB_DETAILS = "jobDetails";
private static final String DB_ISDONE = "jobIsDone";
private SQLiteDatabase JobListDatabase;
private final Context jobContext;
/**
* constructor t
*/
public IntDataBaseHelper (Context context) {
super (context, DB_NAME,null, 1);
this.jobContext = context;
DB_PATH = jobContext.getDatabasePath(DB_NAME).getPath();
}
public void openDataBase() {
// open the database
String JobListPath = DB_PATH;
JobListDatabase = SQLiteDatabase.openDatabase(
JobListPath,null,SQLiteDatabase.OPEN_READONLY);
}
// Getting Job Count
public ArrayList<String> getJobList() {
ArrayList<String> JobList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(DB_TABLE,new String[]
{DB_COLUMN},null,null,null,null,null);
while(cursor.moveToNext()){
int index = cursor.getColumnIndex(DB_COLUMN);
JobList.add(cursor.getString(index));
}
cursor.close();
db.close();
return JobList;
}
// Gets the job state if it has been competed or not
public ArrayList<String> getIsDone() {
ArrayList<String> IsDone = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(DB_TABLE,new String[]{DB_ISDONE},null,null,null,null,null);
while(cursor.moveToFirst()){
int index = cursor.getColumnIndex(DB_ISDONE);
IsDone.add(cursor.getString(index));
}
cursor.close();
db.close();
return IsDone;
}
@Override
public synchronized void close(){
if(JobListDatabase !=null){
JobListDatabase.close();
super.close();
}
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
