我是编程的新手，所以请多多包涵（我正在学习在线课程）。
在本课的某个时刻，我们应该在Java类中创建一个数据库，然后将在主要活动（称为CatalogActivity）的onCreate方法中创建一个名为“ pets”的表。
这时，我已经按照应有的格式下载了应用程序（以确保我之前没有在代码中犯错），但是当我在模拟器上运行该应用程序时，没有表已创建。
这个想法是，当我运行该应用程序时，应该创建一个名为housing.db的数据库，并在其中创建一个名为“ pets”的表。该表在PetDbHelper.java类中定义。
在Android Studio终端中进行搜索时，在housing.db中看不到任何表。因此，我将housing.db下载到我的PC上，并使用SQL浏览器打开它-仍然没有“ pets”表。看起来由于某种原因，无法创建表：（
我不知道为什么要遵循所有指示。 请问有人建议如何解决此问题吗？
以下是代码的链接：https://github.com/soralka/PetsApp_error
谢谢！
Soralka
当我使用CommonSQLiteUtilities类时，这里是日志：
07-18 19:37:44.344 15867-15867/? I/le.android.pet: Not late-enabling -Xcheck:jni (already on)
07-18 19:37:44.416 15867-15867/? W/le.android.pet: Unexpected CPU variant for X86 using defaults: x86
07-18 19:37:44.662 15867-15867/com.example.android.pets I/le.android.pet: The ClassLoaderContext is a special shared library.
07-18 19:37:45.027 15867-15867/com.example.android.pets W/le.android.pet: JIT profile information will not be recorded: profile file does not exits.
07-18 19:37:45.051 15867-15867/com.example.android.pets I/chatty: uid=10083(com.example.android.pets) identical 10 lines
07-18 19:37:45.051 15867-15867/com.example.android.pets W/le.android.pet: JIT profile information will not be recorded: profile file does not exits.
07-18 19:37:45.137 15867-15867/com.example.android.pets I/InstantRun: starting instant run server: is main process
07-18 19:37:45.840 15867-15867/com.example.android.pets W/le.android.pet: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (light greylist, reflection)
07-18 19:37:45.850 15867-15867/com.example.android.pets W/le.android.pet: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (light greylist, reflection)
07-18 19:37:46.066 15867-15867/com.example.android.pets D/SQLITE_CSU: DatabaseList Row 1 Name=main File=/data/user/0/com.example.android.pets/databases/shelter.db
07-18 19:37:46.068 15867-15867/com.example.android.pets D/SQLITE_CSU: Database Version = 1
07-18 19:37:46.071 15867-15867/com.example.android.pets D/SQLITE_CSU: Table Name = android_metadata Created Using = CREATE TABLE android_metadata (locale TEXT)
07-18 19:37:46.073 15867-15867/com.example.android.pets D/SQLITE_CSU: Table = android_metadata ColumnName = locale ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
07-18 19:37:46.074 15867-15867/com.example.android.pets D/SQLITE_CSU: Table Name = pets Created Using = CREATE TABLE pets (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, breed TEXT, gender INTEGER NOT NULL, weight INTEGER NOT NULL DEFAULT 0)
07-18 19:37:46.077 15867-15867/com.example.android.pets D/SQLITE_CSU: Table = pets ColumnName = _id ColumnType = INTEGER Default Value = null PRIMARY KEY SEQUENCE = 1
07-18 19:37:46.078 15867-15867/com.example.android.pets D/SQLITE_CSU: Table = pets ColumnName = name ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
07-18 19:37:46.079 15867-15867/com.example.android.pets D/SQLITE_CSU: Table = pets ColumnName = breed ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
Table = pets ColumnName = gender ColumnType = INTEGER Default Value = null PRIMARY KEY SEQUENCE = 0
Table = pets ColumnName = weight ColumnType = INTEGER Default Value = 0 PRIMARY KEY SEQUENCE = 0
07-18 19:37:46.080 15867-15867/com.example.android.pets D/SQLITE_CSU: Table Name = sqlite_sequence Created Using = CREATE TABLE sqlite_sequence(name,seq)
07-18 19:37:46.082 15867-15867/com.example.android.pets D/SQLITE_CSU: Table = sqlite_sequence ColumnName = name ColumnType = Default Value = null PRIMARY KEY SEQUENCE = 0
Table = sqlite_sequence ColumnName = seq ColumnType = Default Value = null PRIMARY KEY SEQUENCE = 0
07-18 19:37:46.134 15867-15867/com.example.android.pets D/OpenGLRenderer: Skia GL Pipeline
07-18 19:37:46.260 15867-15886/com.example.android.pets I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasWideColorDisplay retrieved: 0
07-18 19:37:46.262 15867-15886/com.example.android.pets I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasHDRDisplay retrieved: 0
07-18 19:37:46.262 15867-15886/com.example.android.pets I/OpenGLRenderer: Initialized EGL, version 1.4
07-18 19:37:46.262 15867-15886/com.example.android.pets D/OpenGLRenderer: Swap behavior 1
07-18 19:37:46.262 15867-15886/com.example.android.pets W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
07-18 19:37:46.263 15867-15886/com.example.android.pets D/OpenGLRenderer: Swap behavior 0
07-18 19:37:46.284 15867-15886/com.example.android.pets D/EGL_emulation: eglCreateContext: 0xe4fbebc0: maj 3 min 0 rcv 3
07-18 19:37:46.347 15867-15886/com.example.android.pets D/EGL_emulation: eglMakeCurrent: 0xe4fbebc0: ver 3 0 (tinfo 0xe79c7930)
07-18 19:37:46.534 15867-15886/com.example.android.pets D/EGL_emulation: eglMakeCurrent: 0xe4fbebc0: ver 3 0 (tinfo 0xe79c7930)
答案 0 :(得分：0)
根据您的代码，我看不到任何问题。
onCreate方法将无法运行，因此可能未应用任何更正更改（如果有）。 通过添加以下行来修改CatalogActivity：-
displayDatabaseInfo();
结果将按预期更新EditText（在pets数据库中显示0行）。
如果基础表不存在，那么如果您添加了上面的行，您将在：-
的行中遇到异常07-17 01:28:51.001 1321-1321/pets.pets E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{pets.pets/pets.pets.CatalogActivity}: android.database.sqlite.SQLiteException: no such table: notatable (code 1): , while compiling: SELECT * FROM notatable
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.database.sqlite.SQLiteException: no such table: notatable (code 1): , while compiling: SELECT * FROM notatable
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
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:1314)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
at pets.pets.CatalogActivity.displayDatabaseInfo(CatalogActivity.java:40)
at pets.pets.CatalogActivity.onCreate(CatalogActivity.java:22)
at android.app.Activity.performCreate(Activity.java:5008)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
通过将表名更改为 notatable 即
来强制注释Cursor cursor = db.rawQuery("SELECT * FROM " + "notatable", null);
从Are there any methods that assist with resolving common SQLite issues?
添加 CommonSQLiteUtilities 类，然后添加以下行：-
CommonSQLiteUtilities.logDatabaseInfo(mDbHelper.getWritableDatabase());
结果包含：-
07-17 01:36:51.191 1399-1399/? D/SQLITE_CSU: DatabaseList Row 1 Name=main File=/data/data/pets.pets/databases/shelter.db
Database Version = 1
Table Name = android_metadata Created Using = CREATE TABLE android_metadata (locale TEXT)
Table = android_metadata ColumnName = locale ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
Table Name = pets Created Using = CREATE TABLE pets (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, breed TEXT, gender INTEGER NOT NULL, weight INTEGER NOT NULL DEFAULT 0)
Table = pets ColumnName = _id ColumnType = INTEGER Default Value = null PRIMARY KEY SEQUENCE = 1
Table = pets ColumnName = name ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
Table = pets ColumnName = breed ColumnType = TEXT Default Value = null PRIMARY KEY SEQUENCE = 0
Table = pets ColumnName = gender ColumnType = INTEGER Default Value = null PRIMARY KEY SEQUENCE = 0
Table = pets ColumnName = weight ColumnType = INTEGER Default Value = 0 PRIMARY KEY SEQUENCE = 0
Table Name = sqlite_sequence Created Using = CREATE TABLE sqlite_sequence(name,seq)
Table = sqlite_sequence ColumnName = name ColumnType = Default Value = null PRIMARY KEY SEQUENCE = 0
Table = sqlite_sequence ColumnName = seq ColumnType = Default Value = null PRIMARY KEY SEQUENCE = 0
进一步确认该表已创建。
上面的测试是使用以下代码完成的：-
public class CatalogActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_catalog);
//displayDatabaseInfo();
PetDbHelper mDbHelper = new PetDbHelper(this);
SQLiteDatabase db = mDbHelper.getReadableDatabase();
displayDatabaseInfo();
CommonSQLiteUtilities.logDatabaseInfo(mDbHelper.getWritableDatabase());
}
/**
* Temporary helper method to display information in the onscreen TextView about the state of
* the pets database.
*/
private void displayDatabaseInfo() {
// To access our database, we instantiate our subclass of SQLiteOpenHelper
// and pass the context, which is the current activity.
PetDbHelper mDbHelper = new PetDbHelper(this);
// Create and/or open a database to read from it
SQLiteDatabase db = mDbHelper.getReadableDatabase();
// Perform this raw SQL query "SELECT * FROM pets"
// to get a Cursor that contains all rows from the pets table.
Cursor cursor = db.rawQuery("SELECT * FROM " + PetContract.PetEntry.TABLE_NAME, null);
try {
// Display the number of rows in the Cursor (which reflects the number of rows in the
// pets table in the database).
TextView displayView = (TextView) findViewById(R.id.text_view_pet);
displayView.setText("Number of rows in pets database table: " + cursor.getCount());
} finally {
// Always close the cursor when you're done reading from it. This releases all its
// resources and makes it invalid.
cursor.close();
}
}
}
public class PetDbHelper extends SQLiteOpenHelper {
public static final String LOG_TAG = PetDbHelper.class.getSimpleName();
/**
* Name of the database file
*/
private static final String DATABASE_NAME = "shelter.db";
/**
* Database version. If you change the database schema, you must increment the database version.
*/
private static final int DATABASE_VERSION = 1;
/**
* Constructs a new instance of {@link PetDbHelper}.
*
* @param context of the app
*/
public PetDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
/**
* This is called when the database is created for the first time.
*/
@Override
public void onCreate(SQLiteDatabase db) {
// Create a String that contains the SQL statement to create the pets table
String SQL_CREATE_PETS_TABLE = "CREATE TABLE " + PetContract.PetEntry.TABLE_NAME + " ("
+ PetContract.PetEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ PetContract.PetEntry.COLUMN_PET_NAME + " TEXT NOT NULL, "
+ PetContract.PetEntry.COLUMN_PET_BREED + " TEXT, "
+ PetContract.PetEntry.COLUMN_PET_GENDER + " INTEGER NOT NULL, "
+ PetContract.PetEntry.COLUMN_PET_WEIGHT + " INTEGER NOT NULL DEFAULT 0);";
// Execute the SQL statement
db.execSQL(SQL_CREATE_PETS_TABLE);
}
/**
* This is called when the database needs to be upgraded.
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// The database is still at version 1, so there's nothing to do be done here.
}
}
public final class PetContract {
private PetContract() {}
public static final class PetEntry implements BaseColumns {
public static final String TABLE_NAME = "pets";
public static final String _ID = BaseColumns._ID;
public static final String COLUMN_PET_NAME = "name";
public static final String COLUMN_PET_BREED = "breed";
public static final String COLUMN_PET_GENDER = "gender";
public static final String COLUMN_PET_WEIGHT = "weight";
/* Possible values for gender. */
public static final int GENDER_UNKNOWN = 0;
public static final int GENDER_MALE = 1;
public static final int GENDER_FEMALE = 2;
}
}
public class CommonSQLiteUtilities {
public static final boolean ERROR_CHECKING_ON = true;
public static final boolean ERROR_CHECKING_OFF = false;
// SQLite MASTER TABLE definitions
static final String SQLITE_MASTER = "sqlite_master";
static final String SM_TABLE_TYPE_COLUMN = "type";
static final String SM_NAME_COLUMN = "name";
static final String SM_TABLENAME_COLUMN = "tbl_name";
static final String SM_ROOTPAGE_COLUMN = "rootpage";
static final String SM_SQL_COLUMN = "sql";
static final String SM_TYPE_TABLE = "table";
static final String SM_TYPE_INDEX = "index";
static final String PRAGMA_STATEMENT = "PRAGMA ";
static final String PRAGMA_DATABASELIST = "database_list";
static final String PRAGMA_USERVERSION = "user_version";
static final String PRAGMA_ENCODING = "encoding";
static final String PRAGMA_FOREIGNKEYLIST = "foreign_key_list";
static final String PRAGMA_INDEXINFO = "index_info";
static final String PRAGMA_INDEXLIST = "index_list";
static final String PRAGMA_TABLEINFO = "table_info";
static final String PRAGMA_DBLIST_SEQ_COL = "seq";
static final String PRAGMA_DBLIST_NAME_COL = "name";
static final String PRAGMA_DBLIST_FILE_COL = "file";
static final String PRAGMA_TABLEINFO_CID_COL = "cid";
static final String PRAGMA_TABLEINFO_NAME_COl = "name";
static final String PRAGMA_TABLEINFO_TYPE_COL = "type";
static final String PRAGMA_TABLEINFO_NOTNULL_COL = "notnull";
static final String PRAGMA_TABLEINFO_DEFAULTVALUE_COL = "dflt_value";
static final String PRAGMA_TABLEINFO_PRIMARYKEY_COL = "pk";
static final String CSU_TAG = "SQLITE_CSU";
private CommonSQLiteUtilities() {}
/**
* Write Database information to the log;
* Information wrttien is:
* the database path, (will/should show connected databases)
* the version number (note! user version i.e. version coded in DBHelper),
* the tables in the database (includes android_metadata but not sqlite_master),
* the columns of the tables
* @param db The SQLite database to be interrogated
*/
public static void logDatabaseInfo(SQLiteDatabase db) {
// Issue PRAGMA database_list commnand
Cursor dblcsr = db.rawQuery(PRAGMA_STATEMENT + PRAGMA_DATABASELIST,null);
// Write databases to the log
while (dblcsr.moveToNext()) {
Log.d(CSU_TAG,"DatabaseList Row " + Integer.toString(dblcsr.getPosition() + 1) +
" Name=" + dblcsr.getString(dblcsr.getColumnIndex(PRAGMA_DBLIST_NAME_COL)) +
" File=" + dblcsr.getString(dblcsr.getColumnIndex(PRAGMA_DBLIST_FILE_COL))
);
}
dblcsr.close();
// Issue PRAGMA user_version to get the version and write to the log
//Note! to set user_version use execSQL not rawQuery
Cursor uvcsr = db.rawQuery(PRAGMA_STATEMENT + PRAGMA_USERVERSION,null);
while (uvcsr.moveToNext()) {
Log.d(CSU_TAG,"Database Version = " +
Integer.toString(uvcsr.getInt(uvcsr.getColumnIndex(PRAGMA_USERVERSION))));
}
uvcsr.close();
// Select all table entry rows from sqlite_master
Cursor tlcsr = db.rawQuery("SELECT * FROM " +
SQLITE_MASTER + " WHERE " +
SM_TABLE_TYPE_COLUMN + "='" + SM_TYPE_TABLE + "'"
,null);
// For each table write table information to the log
// (inner loop gets column info per table)
while (tlcsr.moveToNext()) {
String current_table = tlcsr.getString(tlcsr.getColumnIndex(SM_TABLENAME_COLUMN));
Log.d(CSU_TAG,
"Table Name = " + current_table +
" Created Using = " + tlcsr.getString(tlcsr.getColumnIndex(SM_SQL_COLUMN)),
null
);
// Issue PRAGMA tabel_info for the current table
Cursor ticsr = db.rawQuery(PRAGMA_STATEMENT + PRAGMA_TABLEINFO +
"(" + current_table + ")",
null
);
// Write column info (see headings below) to the log
while (ticsr.moveToNext()) {
Log.d(CSU_TAG,"Table = " +
current_table +
" ColumnName = " +
ticsr.getString(ticsr.getColumnIndex(PRAGMA_TABLEINFO_NAME_COl)) +
" ColumnType = " +
ticsr.getString(ticsr.getColumnIndex(PRAGMA_TABLEINFO_TYPE_COL)) +
" Default Value = " +
ticsr.getString(ticsr.getColumnIndex(PRAGMA_TABLEINFO_DEFAULTVALUE_COL)) +
" PRIMARY KEY SEQUENCE = " + Integer.toString(
ticsr.getInt(ticsr.getColumnIndex(PRAGMA_TABLEINFO_PRIMARYKEY_COL))
)
);
}
ticsr.close();
}
tlcsr.close();
}
/**
* Generic get all rows from an SQlite table,
* allowing the existence of the table to be checked and also
* allowing the ROWID to be added AS a supplied string
*
* @param db The SQLiteDatabase
* @param tablename The name of the table from which the
* returned cursor will be created from;
* Note!
* @param use_error_checking Whether ot not to try to detect errors
* currently just table doesn't exist,
* true to turn on, false to turn off
* ERROR_CHECKING_ON = true
* ERROR_CHECKING_OFF = false
* @param forceRowidAs If length of string passed is 1 or greater
* then a column, as an alias of ROWID, will be
* added to the cursor
* @return the extracted cursor, or in the case of the
* underlying table not existing an empty cursor
* with no columns
*/
public static Cursor getAllRowsFromTable(SQLiteDatabase db,
String tablename,
boolean use_error_checking,
String forceRowidAs) {
String[] columns = null;
// Tablename must be at least 1 character in length
if (tablename.length() < 1) {
Log.d(CSU_TAG,new Object(){}.getClass().getEnclosingMethod().getName() +
" is finishing as the provided tablename is less than 1 character in length"
);
return new MatrixCursor(new String[]{});
}
// If use_error_checking is true then check that the table exists
// in the sqlite_master table
if (use_error_checking) {
Cursor chkcsr = db.query(SQLITE_MASTER,null,
SM_TABLE_TYPE_COLUMN + "=? AND "
+ SM_TABLENAME_COLUMN + "=?",
new String[]{SM_TYPE_TABLE,tablename},
null,null,null
);
// Ooops table is not in the Database so return an empty
// column-less cursor
if (chkcsr.getCount() < 1) {
Log.d(CSU_TAG,"Table " + tablename +
" was not located in the SQLite Database Master Table."
);
// return empty cursor with no columns
return new MatrixCursor(new String[]{});
}
chkcsr.close();
}
// If forcing an alias of ROWID then user ROWID AS ???, *
if(forceRowidAs != null && forceRowidAs.length() > 0) {
columns = new String[]{"rowid AS " +forceRowidAs,"*"};
}
// Finally return the Cursor but trap any exceptions
try {
return db.query(tablename, columns, null, null, null, null, null);
} catch (Exception e) {
Log.d(CSU_TAG,"Exception encountered but trapped when querying table " + tablename +
" Message was: \n" + e.getMessage());
Log.d(CSU_TAG,"Stacktrace was:");
e.printStackTrace();
return new MatrixCursor(new String[]{});
}
}
/**
* Create and return a Cursor devoid of any rows and columns
* Not used, prehaps of very little use.
* @param db The Sqlite database in which the cursor is to be created
* @return The empty Cursor
*/
private static Cursor getEmptyColumnLessCursor(SQLiteDatabase db) {
return new MatrixCursor(new String[]{});
}
/**
* Write column names in the passed Cursor to the log
* @param csr The Cursor to be inspected.
*/
public static void logCursorColumns(Cursor csr) {
Log.d(CSU_TAG,
new Object(){}.getClass().getEnclosingMethod().getName() +
" invoked. Cursor has the following " +
Integer.toString(csr.getColumnCount())+
" columns.");
int position = 0;
for (String column: csr.getColumnNames()) {
position++;
Log.d(CSU_TAG,"Column Name " +
Integer.toString(position) +
" is "
+ column
);
}
}
/**
* Write the contents of the Cursor to the log
* @param csr The Cursor that is to be displayed in the log
*/
public static void logCursorData(Cursor csr) {
int columncount = csr.getColumnCount();
int rowcount = csr.getCount();
int csrpos = csr.getPosition(); //<<< added 20171016
Log.d(CSU_TAG,
new Object(){}.getClass().getEnclosingMethod().getName() +
" Cursor has " +
Integer.toString(rowcount) +
" rows with " +
Integer.toString(columncount) + " columns."
);
csr.moveToPosition(-1); //Ensure that all rows are retrieved <<< added 20171016
while (csr.moveToNext()) {
String unobtainable = "unobtainable!";
String logstr = "Information for row " + Integer.toString(csr.getPosition() + 1) + " offset=" + Integer.toString(csr.getPosition());
for (int i=0; i < columncount;i++) {
logstr = logstr + "\n\tFor Column " + csr.getColumnName(i);
switch (csr.getType(i)) {
case Cursor.FIELD_TYPE_NULL:
logstr = logstr + " Type is NULL";
break;
case Cursor.FIELD_TYPE_FLOAT:
logstr = logstr + "Type is FLOAT";
break;
case Cursor.FIELD_TYPE_INTEGER:
logstr = logstr + " Type is INTEGER";
break;
case Cursor.FIELD_TYPE_STRING:
logstr = logstr + " Type is STRING";
break;
case Cursor.FIELD_TYPE_BLOB:
logstr = logstr + " Type is BLOB";
break;
}
String strval_log = " value as String is ";
String lngval_log = " value as long is ";
String dblval_log = " value as double is ";
String blbval_log = "";
try {
strval_log = strval_log + csr.getString(i);
lngval_log = lngval_log + csr.getLong(i);
dblval_log = dblval_log + csr.getDouble(i);
} catch (Exception e) {
strval_log = strval_log + unobtainable;
lngval_log = lngval_log + unobtainable;
dblval_log = dblval_log + unobtainable;
try {
blbval_log = " value as blob is " +
getBytedata(csr.getBlob(i),24);
} catch (Exception e2) {
e2.printStackTrace();
}
}
logstr = logstr + strval_log + lngval_log + dblval_log + blbval_log;
}
Log.d(CSU_TAG,logstr);
}
csr.moveToPosition(csrpos); // restore cursor position <<< added 20171016
}
/**
* Return a hex string of the given byte array
* @param bytes The byte array to be converted to a hexadecimal string
* @param limit the maximum number of bytes;
* note returned string will be up to twice as long
* @return The byte array represented as a hexadecimal string
*/
private static String getBytedata(byte[] bytes, int limit) {
if (bytes.length < limit) {
return convertBytesToHex(bytes);
} else {
byte[] subset = new byte[limit];
System.arraycopy(bytes,0,subset,0,limit);
return convertBytesToHex(subset);
}
}
// HEX characters as a char array for use by convertBytesToHex
private final static char[] hexarray = "0123456789ABCDEF".toCharArray();
/**
* Return a hexadecimal string representation of the passed byte array
* @param bytes The byte array to be represented.
* @return The string representing the byte array as hexadecimal
*/
private static String convertBytesToHex(byte[] bytes) {
char[] hexstr = new char[bytes.length * 2];
for (int i=0; i < bytes.length; i++) {
int h = bytes[i] & 0xFF;
hexstr[i * 2] = hexarray[h >>> 4];
hexstr[i * 2 + 1] = hexarray[h & 0xF];
}
return new String(hexstr);
}
}
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".CatalogActivity">
<TextView
android:id="@+id/text_view_pet"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
答案 1 :(得分：0)
我发现主要问题是什么：我正在使用具有API 28的仿真器。显然，尝试访问数据库时，高于API 23的问题都是一个问题。
所以我做了一个新的模拟器API 23，现在我在权限等方面没有任何问题。
@MikeT-这似乎就是为什么我一直在努力获取权限的原因。