这个问题在这里已有答案:
我已经使用sqlite插入数据并获取结果,但我所做的是首先显示包含所获取值的列表,如果没有值,则列表显示空视图,指示用户将新项添加到sqlite数据库 . 但是当我尝试这个时它会向我显示一个错误,数据库中没有这样的表 . 我想知道如何检查表是否已创建,还是它有值 . 如何不向用户抛出异常以向表中插入新项 .
数据库:
public class BuisnessDatabaseHandler extends SQLiteOpenHelper {
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "receiptExample";
// Labels table name
private static final String TABLE_LABELS = "buisnesslabels";
private static final String KEY_ID = "id";
private static final String KEY_IMAGE = "image";
private static final String KEY_STATUS="status";
private static final String KEY_UPLOADSTATUS = "uplaodstatus";
private static final String KEY_USERID="userid";
SQLiteDatabase db;
public BuisnessDatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// Category table create query
String CREATE_CATEGORIES_TABLE = "CREATE TABLE " + TABLE_LABELS + "("
+ KEY_ID + " INTEGER PRIMARY KEY,"
+ KEY_IMAGE + " BLOB,"
+ KEY_STATUS + " TEXT,"
+ KEY_UPLOADSTATUS + " TEXT,"
+ KEY_USERID + " TEXT" + ");";
db.execSQL(CREATE_CATEGORIES_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LABELS);
// Create tables again
onCreate(db);
}
public void insertLabel(byte[] imag,String status,String uploadstatus,String userid){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
//values.put(KEY_ID,id);
values.put(KEY_IMAGE,imag);
values.put(KEY_STATUS,status);
values.put(KEY_UPLOADSTATUS,uploadstatus);
values.put(KEY_USERID,userid);
// Inserting Row
db.insert(TABLE_LABELS, null, values);
db.close(); // Closing database connection
}
public ArrayList<BuisnesslistItems> getAllLabels(){
// List<String> labels = new ArrayList<String>();
ArrayList<BuisnesslistItems>labels=new ArrayList<BuisnesslistItems>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_LABELS;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
BuisnesslistItems buisnesslistItems=new BuisnesslistItems();
buisnesslistItems.setImage(cursor.getBlob(1));
buisnesslistItems.setStatus("Status:"+cursor.getString(2));
labels.add(buisnesslistItems);
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning lables
return labels;
}
public String composeJSONfromSQLite(){
ArrayList<HashMap<String, String>> label;
label = new ArrayList<HashMap<String, String>>();
String selectQuery = "SELECT * FROM labels where " + KEY_STATUS + " = '"+"no"+"'";
SQLiteDatabase database = this.getWritableDatabase();
Cursor cursor = database.rawQuery(selectQuery, null);
if (cursor.moveToFirst()) {
String encodedImage = Base64.encodeToString(cursor.getBlob(1), Base64.DEFAULT);
do {
HashMap<String, String> map = new HashMap<String, String>();
map.put(KEY_ID, cursor.getString(0));
map.put(KEY_IMAGE, encodedImage);
map.put(KEY_USERID,cursor.getString(4));
map.put(KEY_STATUS,"yes");
label.add(map);
} while (cursor.moveToNext());
}
database.close();
Gson gson = new GsonBuilder().create();
//Use GSON to serialize Array List to JSON
return gson.toJson(label);
}
/**
* Get Sync status of SQLite
* @return
*/
public String getSyncStatus(){
String msg = null;
if(this.dbSyncCount() == 0){
msg = "Wallet is Sync with cloud!";
}else{
msg = "Wallet needs to be Sync\n";
}
return msg;
}
/**
* Get SQLite records that are yet to be Synced
* @return
*/
public int dbSyncCount(){
int count = 0;
String selectQuery = "SELECT * FROM labels where " +KEY_STATUS+" = '"+"no"+"'";
SQLiteDatabase database = this.getWritableDatabase();
Cursor cursor = database.rawQuery(selectQuery, null);
count = cursor.getCount();
database.close();
return count;
}
/**
* Update Sync status against each User ID
* @param id
* @param status
*/
public void updateSyncStatus(String id, String status){
SQLiteDatabase database = this.getWritableDatabase();
String updateQuery = "Update labels set " + KEY_STATUS + " = '"+ status +"'," + KEY_UPLOADSTATUS + " = 'Uploaded' where " + KEY_ID + "="+"'"+ id +"'";
Log.d("query", updateQuery);
database.execSQL(updateQuery);
database.close();
}
public void deleteUploaded(String status){
SQLiteDatabase database=this.getWritableDatabase();
String deleteQuery="Delete From labels where " + KEY_STATUS+ " = 'yes' ";
Log.d("dquery",deleteQuery);
database.execSQL(deleteQuery);
database.close();
}
末页:
BuisnessDatabaseHandler db = new BuisnessDatabaseHandler(getApplicationContext());
// Spinner Drop down elements
// List<String> lables = db.getAllLabels();
ArrayList<BuisnesslistItems>list=new ArrayList<BuisnesslistItems>();
list=db.getAllLabels();
buisnessListAdapter = new BuisnessListAdapter(
BuisnessList.this, list);
if (loginSession.isLoggedIn()) {
loginSession.checkLogin();
listView.setAdapter(buisnessListAdapter);
listView.setEmptyView(findViewById(R.id.empty));
Toast.makeText(getApplicationContext(), db.getSyncStatus(), Toast.LENGTH_LONG).show();
}else{
Intent i=new Intent(BuisnessList.this,LoginPAge.class);
startActivity(i);
BuisnessList.this.finish();
}
错误:
Caused by: android.database.sqlite.SQLiteException: no such table: buisnesslabels (code 1): , while compiling: SELECT * FROM buisnesslabels
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:898)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:509)
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:1346)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1285)
at nidhinkumar.reccs.buisnesscarddetails.BuisnessDatabaseHandler.getAllLabels(BuisnessDatabaseHandler.java:81)
at nidhinkumar.reccs.buisnesscarddetails.BuisnessList.syncSQLiteMySQLDB(BuisnessList.java:364)
at nidhinkumar.reccs.buisnesscarddetails.BuisnessList.init(BuisnessList.java:216)
at nidhinkumar.reccs.buisnesscarddetails.BuisnessList.onCreate(BuisnessList.java:143)
I would like to add a condition in the list page to check whether the table exist or not and whether it has values or not
3 回答
您可以使用以下语句来检查表是否存在:
SQLite维护一个名为sqlite_master的表,其中包含数据库中所有表的信息 . 因此,如果结果游标返回计数1,则表示该表存在 . 检查完毕后,使用所需的查询再次查询数据库:
并再次使用
cursor.getCount();
来确定您是否有数据 . 如果cursor.getCount();
返回大于0,那么您将获得所需的数据 .SQLiteStatement:
呼叫
并阅读光标或
if(count> 0) - >表存在
检查它是否存在后,您可以查询行上的计数等 . 也许您必须检查表中是否存在特定列
Manual way of doing it
请访问以下链接并下载DBrowser:Sqlite DBBrowser
现在,转到Android设备监视器
扩展数据
再次展开其中的数据
然后使用您的应用包名称搜索文件夹
然后在其中打开数据库文件夹
将该数据库文件展开并拉入本地,同时拉出
.sqlite
扩展名保存打开DBBrowser并打开本地数据库 .
您现在可以检查表已创建或其中有行 .
EDIT
将
DATABASE_VERSION = 1
更改为DATABASE_VERSION = 2
因此,每当您更改onCreate()
和onUpgrade()
内的任何内容时,都会增加数据库版本 .要检查您的表是否有行,