我的应用程序崩溃了，我试图读取一个预建的db并从那里加载列中的内容，但是目前，它在启动时崩溃了，并认为它与我的DHhandler以及它如何设置GetJobList有关，但是我对Android和一般编程，所以我不确定
DBhandler在下面
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 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{
private static String DB_PATH ="C:\\Users\\joelg\\AndroidStudioProjects\\CLAPP\\app\\build\\intermediates\\assets";
private static String DB_NAME = "JobList";
private static String DB_COLUMN = " JobNM";
private static String DB_TABLE = "Job";
private static String DB_JOB_IS_DONE = "JobComplete";
private SQLiteDatabase JobListDatabase;
private final Context jobContext;
/**
* constructor t
*/
public IntDataBaseHelper (Context context) {
super (context, DB_NAME,null, 1);
this.jobContext = context;
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing database already exists
}else{
// calling this method will create an empty database
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e){
throw new Error("Error copying database");
}
}
}
// check if database exists to avoid recopying it
private boolean checkDataBase (){
SQLiteDatabase checkDB = null;
try{
String JobListPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(JobListPath, null,
SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
// database doesnt exist yet
}
if(checkDB !=null){
checkDB.close();
}
return checkDB !=null ? true : false;
}
// copies db from local assets file, were it can be accessed and handled
private void copyDataBase() throws IOException {
// open local database as the input stream
InputStream JobInput = jobContext.getAssets().open(DB_NAME);
// path to the just created empty database
String OutFileName = DB_PATH + DB_NAME;
// open the empty db as the output stra,
OutputStream myOutPut = new FileOutputStream(OutFileName);
// transfer bytes from the input file to the output file
byte[] buffer = new byte[1024];
int length;
while ((length = JobInput.read(buffer))>0){
myOutPut.write(buffer,0,length);
}
myOutPut.flush();
myOutPut.close();
JobInput.close();
}
public void openDataBase() throws SQLiteException {
// open the database
String JobListPath = DB_PATH+DB_NAME;
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;
}
@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) {
}
}
这是logcat的输出
10-24 03:07:05.081 11072-11072/com.example.joelg.clapp E/SQLiteLog: (1) no such table: job
10-24 03:07:05.084 11072-11072/com.example.joelg.clapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.joelg.clapp, PID: 11072
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.joelg.clapp/com.example.joelg.clapp.MainActivity}: android.database.sqlite.SQLiteException: no such table: job (code 1): , while compiling: SELECT jobNM FROM job
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: android.database.sqlite.SQLiteException: no such table: job (code 1): , while compiling: SELECT jobNM FROM job
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1318)
at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1165)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1036)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1204)
at
com.example.joelg.clapp.IntDataBaseHelper.getJobList(IntDataBaseHelper.java:128)
at
com.example.joelg.clapp.MainActivity.onCreate(MainActivity.java:46)
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)
这是作业数据库文件的位置
这是最新的错误日志
[ 10-24 05:22:39.920
1508:
2079 D/ ]
SurfaceInterface::setAsyncMode: set async mode 1
10-24 05:22:39.925 1611-1631/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:39.925 1611-1631/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:39.925 1611-1631/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:39.938 1611-1631/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:40.523 1611-1628/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:40.523 1611-1628/? E/ResourcesManager: failed to add asset path
/data/app/com.example.joelg.clapp-0JSJFIAy0bMCNOuIEgUs3g==/base.apk
10-24 05:22:42.973 1508-1598/? E/TaskPersister: File error accessing recents
directory (directory doesn't exist?).
10-24 05:22:53.636 1508-1598/? E/TaskPersister: File error accessing recents
directory (directory doesn't exist?).
10-24 05:22:54.924 1508-1521/? E/memtrack: Couldn't load memtrack module
10-24 05:23:26.999 1508-1521/? E/memtrack: Couldn't load memtrack module
10-24 05:23:27.010 1508-1521/? E/memtrack: Couldn't load memtrack module
10-24 05:23:39.285 1508-1525/? E/BatteryStatsService: modem info is invalid:
`ModemActivityInfo{ mTimestamp=0 mSleepTimeMs=0 mIdleTimeMs=0 mTxTimeMs[]=
[0, 0, 0, 0, 0] mRxTimeMs=0 mEnergyUsed=0}`
10-24 05:23:43.109 1508-1521/? E/memtrack: Couldn't load memtrack module
10-24 05:24:00.005 1508-1521/? E/memtrack: Couldn't load memtrack module
最新的logcat输出
10-24 12:01:30.319 2669-2669/? E/SQLiteLog: (14) cannot open file at line 35648 of [036ebf729e]
10-24 12:01:30.319 2669-2669/? E/SQLiteLog: (14) os_unix.c:35648: (2) open(/data/user/0/com.example.joelg.clapp/databases/JobList) -
10-24 12:01:30.320 2669-2669/? E/SQLiteDatabase: Failed to open database '/data/user/0/com.example.joelg.clapp/databases/JobList'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:808)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:793)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:696)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:671)
at com.example.joelg.clapp.CopyDBFromAssets.checkDataBase(CopyDBFromAssets.java:94)
at com.example.joelg.clapp.CopyDBFromAssets.createDataBase(CopyDBFromAssets.java:25)
at com.example.joelg.clapp.MainActivity.onCreate(MainActivity.java:25)
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)
10-24 12:01:30.322 2669-2669/? E/CHECKASSET: Asset JobListcould not be found. Assets that exists are:- CleanIngListTemplate.db.sqbpro JobList.db JobList.db.sqbpro JobList.sqbpro images webkit
10-24 12:01:30.322 2669-2669/? E/CREATEDB: Error getting asset JobList
10-24 12:01:30.325 2669-2669/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.joelg.clapp, PID: 2669
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.joelg.clapp/com.example.joelg.clapp.MainActivity}: java.lang.RuntimeException: No Usable Database exists or was copied from the assets.
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.RuntimeException: No Usable Database exists or was copied from the assets.
at com.example.joelg.clapp.MainActivity.onCreate(MainActivity.java:34)
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)
最佳答案
根据评论对问题进行回应。
1）至关重要的是，复制到资产文件夹中的文件必须具有与数据库完全相同的名称。因此，如果要将数据库称为JobList，则该数据库必须是资产文件夹中的文件名。
2）在开始编写代码之前，请先对混淆进行一些解释。如果事情不完全正确，那将是双重打击。不管创建数据库的情况如何。首先，如果数据库不存在，则this.getReadableDatabase();的createDatabase方法中的单行IntDataBaseHelper将运行。但是，即使在您创建IntDataBaseHelper类的实例时，即使该命令没有运行（例如，注释掉），所有尝试打开数据库的尝试也会尝试创建它。在onCreate方法中缺少代码的情况下，结果将是一个空的数据库，实际上没有任何表*（存在表sqlite_master和android_metadata，但它们是系统类型表）**
因此，我决定将数据库的创建/复制从DBHelper中分离出来，并希望使代码发出更具描述性的消息。
因此，我建议您使用该代码。
首先，有一个新类，我称为CopyDBFromAssets。基本上，这是来自IntDatabaseHelper的代码，但是写的时间更长。有一个新的方法checkAssetExists，用它的名字应该是不言而喻的重新使用它。
调用MainActivity有所不同。而不是获取IntDatabaseHelper的实例。该代码最初在新的createDatabase类中调用CopyDBFromAssets方法，该方法返回一个布尔值。
如果一切正常，则返回true（有关文件刷新和关闭的警告，如果其中有异常，它也应该返回false）。
如果情况不正确，则返回false，在这种情况下，将发出运行时异常。
如果为true，则创建IntDatabaseHelper的实例，并且应该都很好。
CopyDBFromAssets
1）创建一个新的类CopyDBFromAssets.java，然后复制以下代码：-
public class CopyDBFromAssets {
boolean copied = false;
public static boolean createDataBase(Context context, String databasename) {
boolean copied = false;
boolean dbExist = checkDataBase(context, databasename);
if(!dbExist) {
// calling this method will create an empty database
// which will hopefully be overidden, if not then
// empty database will exist ?????????
//this.getReadableDatabase(); <<<<< NOTE Commented out as empty db with no tables is useless
if (!checkAssetExists(context, databasename, "")) {
Log.e("CREATEDB", "Error getting asset " + databasename);
} else {
return copyDataBase(context, databasename);
}
return false;
}
return true;
}
private static boolean checkAssetExists(Context context, String assetfile, String path) {
boolean rv = false; // assume asset file doesn't exist
String[] assetsfound = new String[]{};
// Get the list of assets at the given path
try {
assetsfound = context.getAssets().list(path);
} catch (IOException e) {
Log.e("CHECKASSET","IO Exception when checking for the asset file." + e.getMessage());
return false;
}
// Check to see if the desired asset (passed assetfile) exists
for (String s: assetsfound) {
if (s.equals(assetfile)) {
rv = true;
break;
}
}
if (rv) {
Log.d("CHECKASSET", "Asset " + assetfile + "was found.");
} else {
String assetlist = "";
for (String s: assetsfound) {
assetlist = assetlist + " " + s;
}
Log.e("CHECKASSET", "Asset " + assetfile +
"could not be found. Assets that exists are:- " +
assetlist
);
}
// Asset not found lets try ignoring case
if (!rv) {
for (String s: assetsfound) {
if ((s.toLowerCase()).equals(assetfile.toLowerCase())) {
Log.e("CHECKASSET","Found asset as " + assetfile +
" but looking for " + s +
", although they are similar the case is different."
);
}
}
}
return rv;
}
// check if database exists to avoid recopying it
private static boolean checkDataBase (Context context, String database){
SQLiteDatabase checkDB = null;
String dbpath = context.getDatabasePath(database).getPath();
try{
checkDB = SQLiteDatabase.openDatabase(dbpath, null,
SQLiteDatabase.OPEN_READONLY);
} catch(SQLiteException e){
// database doesnt exist yet
}
if(checkDB !=null){
checkDB.close();
}
return checkDB !=null ? true : false;
}
// copies db from local assets file, were it can be accessed and handled
private static boolean copyDataBase(Context context, String databasename) {
InputStream asset;
OutputStream db;
int bytescopied = 0;
int length_read;
int buffersize = 16384;
int blockcount = 0;
boolean rv = false;
try {
asset = context.getAssets().open(databasename);
} catch (IOException e) {
Log.e("COPYDB",
"IO Error opening the asset " +
databasename +
". Error Message was " +
e.getMessage()
);
return false;
}
try {
db = new FileOutputStream(context.getDatabasePath(databasename).getPath());
} catch (IOException e) {
Log.e("COPYDB",
"IO Error opening the output file for the database with path " +
databasename +
". error Message was " +
e.getMessage()
);
try {
asset.close();
} catch (IOException e2) {
Log.e("COPYDB",
"IO Error closing the asset. Message was " + e2.getMessage()
);
}
return false;
}
byte[] buffer = new byte[buffersize];
try {
while ((length_read = asset.read(buffer)) > 0) {
db.write(buffer);
bytescopied = bytescopied + length_read;
blockcount++;
rv = true;
}
} catch (IOException e) {
Log.e("COPYDB",
"IO Error Copying Database. Bytes Copied = "
+ bytescopied +
" in " +
blockcount +
" blocks of " +
buffersize
);
}
Log.d("COPYDB","Succesfully copied Database " + databasename + " from the assets." +
" Number of bytes copied = " + bytescopied +
" in " + blockcount + " blocks of length " + buffersize
);
try {
db.flush();
db.close();
asset.close();
} catch (IOException e) {
Log.e("COPYDB",
"IO Error flushing or closing Database or closing asset."
);
}
return rv;
}
}
IntDataBaseHelper
这是精简版，需要注意的一件事是DB_NAME，DB_COLUMN和DB_TABLE已更改为
public static final（因为它们已在其他地方使用）。这是代码：-
public class IntDataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH ="C:\\Users\\joelg\\AndroidStudioProjects\\CLAPP\\app\\build\\intermediates\\assets";
public static final String DB_NAME = "JobList";
public static final String DB_COLUMN = "JobNM";
public static final String DB_TABLE = "Job";
private static String DB_JOB_IS_DONE = "JobComplete";
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;
}
@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) {
}
}
主活动
这只是使用上述代码的示例代码，请注意，如果如果数据库不存在则无法创建数据库，那么将发出运行时异常（以下示例）：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the database (only if it doesn't exists)
// does so by copying from the assets
if (CopyDBFromAssets.createDataBase(this,IntDataBaseHelper.DB_NAME)) {
IntDataBaseHelper myhelper = new IntDataBaseHelper(this);
// Get the data from the database
ArrayList<String> jobs = myhelper.getJobList();
for (String s: jobs) {
Log.d("TESTDB","Found Job " + s);
}
} else {
throw new RuntimeException("No Usable Database exists or was copied from the assets.");
}
}
}
运行示例1（未找到资产文件）
因此，首先假定资产文件夹中的文件名为Job而不是JobList（或JobList以外的其他名称），并假设该应用程序已安装。然后运行上面的代码会导致以下问题：-
按照Windows资源管理器中的资产文件夹：-
10-24 20:31:04.994 2346-2346/? E/SQLiteLog: (14) cannot open file at line 30046 of [9491ba7d73]
10-24 20:31:04.994 2346-2346/? E/SQLiteLog: (14) os_unix.c:30046: (2) open(/data/data/mjt.joblist/databases/JobList) -
10-24 20:31:04.994 2346-2346/? E/SQLiteDatabase: Failed to open database '/data/data/mjt.joblist/databases/JobList'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:806)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:791)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
at mjt.joblist.CopyDBFromAssets.checkDataBase(CopyDBFromAssets.java:93)
at mjt.joblist.CopyDBFromAssets.createDataBase(CopyDBFromAssets.java:25)
at mjt.joblist.MainActivity.onCreate(MainActivity.java:18)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
10-24 20:31:05.004 2346-2346/? E/CHECKASSET: Asset JobListcould not be found. Assets that exists are:- Job images sounds webkit
10-24 20:31:05.004 2346-2346/? E/CREATEDB: Error getting asset JobList
10-24 20:31:05.004 2346-2346/? D/AndroidRuntime: Shutting down VM
--------- beginning of crash
10-24 20:31:05.004 2346-2346/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: mjt.joblist, PID: 2346
java.lang.RuntimeException: Unable to start activity ComponentInfo{mjt.joblist/mjt.joblist.MainActivity}: java.lang.RuntimeException: No Usable Database exists or was copied from the assets.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.RuntimeException: No Usable Database exists or was copied from the assets.
at mjt.joblist.MainActivity.onCreate(MainActivity.java:27)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
10-24 20:31:05.008 738-1262/? W/ActivityManager: Force finishing activity 1 mjt.joblist/.MainActivity
以下各行详细介绍了该问题：
10-24 20:31:05.004 2346-2346/? E/CHECKASSET: Asset JobListcould not be found. Assets that exists are:- Job images sounds webkit
10-24 20:31:05.004 2346-2346/? E/CREATEDB: Error getting asset JobList
那就是找不到JobList，找到的资产是Job（错误命名）的图像，声音和Webkit（最后三个与此无关）。
和运行时异常（第二个）一样：
java.lang.RuntimeException: Unable to start activity ComponentInfo{mjt.joblist/mjt.joblist.MainActivity}: java.lang.RuntimeException: No Usable Database exists or was copied from the assets.
RunExample 2-资产文件正确命名为：-
日志显示：-
10-24 20:43:01.160 8696-8696/? E/SQLiteLog: (14) cannot open file at line 30046 of [9491ba7d73]
10-24 20:43:01.160 8696-8696/? E/SQLiteLog: (14) os_unix.c:30046: (2) open(/data/data/mjt.joblist/databases/JobList) -
10-24 20:43:01.162 8696-8696/? E/SQLiteDatabase: Failed to open database '/data/data/mjt.joblist/databases/JobList'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:806)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:791)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
at mjt.joblist.CopyDBFromAssets.checkDataBase(CopyDBFromAssets.java:93)
at mjt.joblist.CopyDBFromAssets.createDataBase(CopyDBFromAssets.java:25)
at mjt.joblist.MainActivity.onCreate(MainActivity.java:18)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
10-24 20:43:01.169 8696-8696/? D/CHECKASSET: Asset JobListwas found.
10-24 20:43:01.175 8696-8696/? D/COPYDB: Succesfully copied Database JobList from the assets. Number of bytes copied = 98304 in 6 blocks of length 16384
10-24 20:43:01.204 8696-8696/? D/TESTDB: Found Job Job001
10-24 20:43:01.204 8696-8696/? D/TESTDB: Found Job Job002
10-24 20:43:01.204 8696-8696/? D/TESTDB: Found Job Job003
10-24 20:43:01.204 8696-8696/? D/TESTDB: Found Job Job004
引发了一个异常（未找到数据库，就像检查它是否存在一样），但是它没有崩溃，我们看到找到了JobList，并且在6个16k的块中复制了98304个字节。
然后，我们在数据库中看到通过DBHelper方法获得的数据。
运行3-后续运行：-
只是：-
10-24 20:52:34.944 13879-13879/? D/TESTDB: Found Job Job001
10-24 20:52:34.944 13879-13879/? D/TESTDB: Found Job Job002
10-24 20:52:34.944 13879-13879/? D/TESTDB: Found Job Job003
10-24 20:52:34.944 13879-13879/? D/TESTDB: Found Job Job004
关于java - 应用程序崩溃的SQLite DB处理程序，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/46881241/