Java 致命异常：main，尝试对空对象引用调用虚拟方法
我启动应用程序时遇到问题。我得到这个问题，尝试调用一个空对象引用上的虚拟方法。我想这是因为我没有正确创建LoadJobList的实例，但我不能完全确定Java 致命异常：main，尝试对空对象引用调用虚拟方法,java,android,sqlite,nullpointerexception,Java,Android,Sqlite,Nullpointerexception,我启动应用程序时遇到问题。我得到这个问题，尝试调用一个空对象引用上的虚拟方法。我想这是因为我没有正确创建LoadJobList的实例，但我不能完全确定 [ 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 EXC
[ 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)
[ 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)
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());
}
}
[ 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)
[ 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)
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;
}
public ArrayList getJobList（）{
ArrayList作业列表=新建ArrayList（）；
SQLiteDatabase db=this.getReadableDatabase（）；
Cursor Cursor=db.query（db_表，新字符串[]）
{DB_COLUMN}，null，null，null，null，null，null）；
while（cursor.moveToNext（））{
int index=cursor.getColumnIndex（DB_列）；
JobList.add（cursor.getString（index））；
}
cursor.close（）；
db.close（）；
返回工作清单；
}
[ 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)
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) {
}
}
package com.example.joelg.clapp；
导入android.content.Context；
导入android.database.Cursor；
导入android.database.sqlite.SQLiteDatabase；
导入android.database.sqlite.SQLiteException；
导入android.database.sqlite.SQLiteOpenHelper；
导入android.util.Log；
导入java.io.FileOutputStream；
导入java.io.IOException；
导入java.io.InputStream；
导入java.io.OutputStream；
导入java.util.ArrayList；
/**
*由joelg于2017年10月22日创建。
*/
公共类IntDataBaseHelper扩展了SQLiteOpenHelper{
公共静态字符串DB_PATH=“//data/data/com.example.joelg.clapp/databases”；
公共静态最终字符串DB_NAME=“作业列表”；
私有静态最终字符串DB_COLUMN=“jobNM”；
私有静态最终字符串DB_TABLE=“job”；
公共静态最终字符串DB\u JOB\u DETAILS=“jobDetails”；
私有静态最终字符串DB_ISDONE=“jobistone”；
私有SQLiteDatabase-JobListDatabase；
私人最终语境；
/**
*构造函数t
*/
公共IntDataBaseHelper（上下文）{
super（上下文，DB_名称，null，1）；
this.jobContext=context；
DB_PATH=jobContext.getDatabasePath（DB_NAME.getPath（）；
}
公共void openDataBase（）{
//打开数据库
字符串JobListPath=DB\u路径；
JobListDatabase=SQLiteDatabase.openDatabase(
JobListPath，null，SQLiteDatabase.OPEN\u READONLY）；
}
//获得工作计数
公共阵列列表getJobList（）{
ArrayList作业列表=新建ArrayList（）；
SQLiteDatabase db=this.getReadableDatabase（）；
Cursor Cursor=db.query（db_表，新字符串[]）
{DB_COLUMN}，null，null，null，null，null，null）；
while（cursor.moveToNext（））{
int index=cursor.getColumnIndex（DB_列）；
JobList.add（cursor.getString（index））；
}
cursor.close（）；
db.close（）；
返回工作清单；
}
//获取作业状态（如果已竞争或未竞争）
公共阵列列表getIsDone（）{
ArrayList IsDone=新的ArrayList（）；
SQLiteDatabase db=this.getReadableDatabase（）；
Cursor Cursor=db.query（db_TABLE，新字符串[]{db_ISDONE}，null，null，null，null）；
while（cursor.moveToFirst（））{
int index=cursor.getColumnIndex（DB_ISDONE）；
add（cursor.getString（index））；
}
cursor.close（）；
db.close（）；
返回IsDone；
}
@凌驾
公共同步作废关闭（）{
if（JobListDatabase！=null）{
JobListDatabase.close（）；
super.close（）；
}
}
@凌驾
public void onCreate（SQLiteDatabase db）{
}
@凌驾
public void onUpgrade（SQLiteDatabase db，int-oldVersion，int-newVersion）{
}
}
公共类MainActivity扩展了AppCompatActivity{
[ 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)
IntDataBaseHelper IntDataBaseHelper；
ArrayAdapter mAdapter；
ListView作业；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.header）；
[ 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)
intDataBaseHelper = 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 = myhelper.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());
intDataBaseHelper=新的intDataBaseHelper（此）；
lstJob=（ListView）findViewById（R.id.lstJob）；
LoadJobList（）；
//创建数据库（仅当数据库不存在时）
//通过从资产中复制来实现
if（CopyDBFromAssets.createDataBase（这个，IntDataBaseHelper.DB_名称））{
//从数据库中获取数据
ArrayList jobs=myhelper.getJobList（）；
用于（字符串s:作业）{
日志d（“作业列表”、“找到的作业”+s）；
}
}否则{
抛出新的RuntimeException（“不存在可用的数据库或从资产中复制了可用的数据库”）；
}
}
//将作业加载到屏幕
私有void LoadJobList（）{
ArrayList作业列表=intDataBaseHelper.getJobList（）；
if（mAdapter==null）{
mAdapter=newarrayadapter（这个，R.layout.header，R.id.header）；
mAdapter=newarrayadapter（this，R.layout.row，R.id.BtnComplete）；
mAdapter=newarrayadapter（这个，R.layout.row，R.id.Job\u名称，Joblist）；
lstJob.setAdapter（mAdapter）；
}否则{
mAdapter.clear（）；
mAdapter.addAll（工作列表）；
mAdapter.notifyDataSetChanged（）；
}
}
public void作业完成（视图）{
View parent=（View）View.getParent（）；
TextView taskTextView=（TextView）parent.findViewById（R.id.BtnComplete）；
e（“String”，（String）taskTextView.getText（）；
[ 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)
名为intDataBaseHelper的对象从未初始化，因此它为空。初始化
intDataBaseHelper[ 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)
[ 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)
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 = 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());
}
}
public类MainActivity扩展了AppCompatActivity{
IntDat