[英]Insert, Delete, Retrieve data from and into existing sqlite database in assests folder
我创建了一个sqlite数据库并将其放在我的android项目的资产文件夹中。 现在，我要在此数据库上执行Insert,Delete,Retrieve操作。
我创建了一个新活动，在该活动中，我将输入一个人的详细信息，然后按保存按钮(checkout_btn) ，将该信息保存在现有数据库中。
我不知道这段代码有什么问题。 我没有任何错误，甚至没有数据插入到现有数据库中。
我还想根据此应用程序中用户功能提供的搜索框值，从数据库中添加检索数据(on button click) 。
这是我的代码：
This class talk about my database which is already present in my assets folder in my project. In this database only i have to insert my data from a form.
**DBConstant.Java**
public abstract class DBConstant
{ //database file directory
public static String DATABASE_PATH = "/data/data/activity.test/databases";
//database file name
public static String DATABASE_FILE = "test.db";
//database version
public static int DATABASE_VERSION = 1;
}
**This is my DBOpenHelper.Java file**
**DBOpenHelper.Java**
public class DBOpenHelper extends SQLiteOpenHelper {
public DBOpenHelper(Context context, String path, int version){
super(context, path, null, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
**Below is my DBOperator.Java file**
/**
* Class to manipulate tables & data
* Uses singleton pattern to create single instance
*/
public class DBOperator
{
private static DBOperator instance = null;
private SQLiteDatabase db;
private DBOperator()
{
//path of database file
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
db = SQLiteDatabase.openDatabase(path, null,
SQLiteDatabase.OPEN_READWRITE);
}
/*
* Singleton Pattern
* Why should we avoid multiple instances here?
*/
public static DBOperator getInstance()
{
if (instance==null) instance = new DBOperator();
return instance;
}
/**
* Copy database file
* From assets folder (in the project) to android folder (on device)
*/
public static void copyDB(Context context) throws
IOException,FileNotFoundException{
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
File file = new File(path);
if (!file.exists()){
DBOpenHelper dbhelper = new DBOpenHelper(context, path ,1);
dbhelper.getWritableDatabase();
InputStream is = context.getAssets().open(DBConstant.DATABASE_FILE);
OutputStream os = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer))>0){
os.write(buffer, 0, length);
}
is.close();
os.flush();
os.close();
}
}
/**
* execute sql without returning data, such as alter
* @param sql
*/
public void execSQL(String sql) throws SQLException
{
db.execSQL(sql);
}
/**
* execute sql such as update/delete/insert
* @param sql
* @param args
* @throws SQLException
*/
public void execSQL(String sql, Object[] args) throws SQLException
{
db.execSQL(sql, args);
}
/**
* execute sql query
* @param sql
* @param selectionArgs
* @return cursor
* @throws SQLException
*/
public Cursor execQuery(String sql,String[] selectionArgs) throws
SQLException
{
return db.rawQuery(sql, selectionArgs);
}
/**
* execute query without arguments
* @param sql
* @return
* @throws SQLException
*/
public Cursor execQuery(String sql) throws SQLException
{
return this.execQuery(sql, null);
}
/**
* close database
*/
public void closeDB()
{
if (db!=null) db.close();
}
}
Here is my DBOperator.Java
/**
* Class to manipulate tables & data
* Uses singleton pattern to create single instance
*/
public class DBOperator
{
private static DBOperator instance = null;
private SQLiteDatabase db;
private DBOperator()
{
//path of database file
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
db = SQLiteDatabase.openDatabase(path, null,
SQLiteDatabase.OPEN_READWRITE);
}
/*
* Singleton Pattern
* Why should we avoid multiple instances here?
*/
public static DBOperator getInstance()
{
if (instance==null) instance = new DBOperator();
return instance;
}
/**
* Copy database file
* From assets folder (in the project) to android folder (on device)
*/
public static void copyDB(Context context) throws
IOException,FileNotFoundException{
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
File file = new File(path);
if (!file.exists()){
DBOpenHelper dbhelper = new DBOpenHelper(context, path ,1);
dbhelper.getWritableDatabase();
InputStream is = context.getAssets().open(DBConstant.DATABASE_FILE);
OutputStream os = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer))>0){
os.write(buffer, 0, length);
}
is.close();
os.flush();
os.close();
}
}
/**
* execute sql without returning data, such as alter
* @param sql
*/
public void execSQL(String sql) throws SQLException
{
db.execSQL(sql);
}
/**
* execute sql such as update/delete/insert
* @param sql
* @param args
* @throws SQLException
*/
public void execSQL(String sql, Object[] args) throws SQLException
{
db.execSQL(sql, args);
}
/**
* execute sql query
* @param sql
* @param selectionArgs
* @return cursor
* @throws SQLException
*/
public Cursor execQuery(String sql,String[] selectionArgs) throws
SQLException
{
return db.rawQuery(sql, selectionArgs);
}
/**
* execute query without arguments
* @param sql
* @return
* @throws SQLException
*/
public Cursor execQuery(String sql) throws SQLException
{
return this.execQuery(sql, null);
}
/**
* close database
*/
public void closeDB()
{
if (db!=null) db.close();
}
}
NewActivity.java
public class NewpActivity extends AppCompatActivity
{
String PaFirstName,PaLastName,PaDOB,PaGender,PaContact,PaStreetAPT,PaCity,PaState,country,PaPincode,PaInsurance;
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_newp);
Button signUpBtn = (Button) findViewById(R.id.checkout_btn);
signUpBtn.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
//Running method for updating string variables from input boxes
getValues();
DBOperator.getInstance().execSQL(SQLCommand.NEW_USER, getArgs());
Toast.makeText(getBaseContext(), "Checkout successfully", Toast.LENGTH_SHORT).show();
}
});
}
SQLCommand.java
public abstract class SQLCommand {
public static String NEW_USER = "insert into Patient(PaFirstName,PaLastName,PaDOB,PaGender,PaContact,PaStreetAPT,PaCity,PaState,PaPincode,PaInsurance) values(?,?,?,?,?,?,?,?,?,?)";
}
在copy db方法中，需要在刷新输出流后关闭输入流。
现有代码：
public static void copyDB(Context context) throws
IOException,FileNotFoundException{
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
File file = new File(path);
if (!file.exists()){
DBOpenHelper dbhelper = new DBOpenHelper(context, path ,1);
dbhelper.getWritableDatabase();
InputStream is = context.getAssets().open(DBConstant.DATABASE_FILE);
OutputStream os = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer))>0){
os.write(buffer, 0, length);
}
**is.close();
os.flush();
os.close();**
}
}
更新的代码：
public static void copyDB(Context context) throws
IOException,FileNotFoundException{
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
File file = new File(path);
if (!file.exists()){
DBOpenHelper dbhelper = new DBOpenHelper(context, path ,1);
dbhelper.getWritableDatabase();
InputStream is = context.getAssets().open(DBConstant.DATABASE_FILE);
OutputStream os = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer))>0){
os.write(buffer, 0, length);
}
**os.flush();os.close();
is.close();**
}
}
您需要调用copyDB方法，以便从资产文件夹复制数据库。 否则，将创建一个空数据库。
这应该在尝试获取DBOperator实例之前完成。 设置Activity的ContentView之后，可以立即进行此调用，例如
public class NewpActivity extends AppCompatActivity {
String PaFirstName, PaLastName, PaDOB, PaGender, PaContact, PaStreetAPT, PaCity, PaState, country, PaPincode, PaInsurance;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_newp);
Button signUpBtn = (Button) findViewById(R.id.checkout_btn);
try {
DBOperator.copyDB(this);
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("DB Copy Failed. Issuing runtime exception");
}
signUpBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//Running method for updating string variables from input boxes
//getValues();
//DBOperator.getInstance().execSQL(SQLCommand.NEW_USER, getArgs());
Toast.makeText(getBaseContext(), "Checkout successfully", Toast.LENGTH_SHORT).show();
}
});
}
}
请注意，在运行更正的代码之前，您应该删除应用程序的数据或卸载应用程序，以便删除数据库（否则，copyDB方法将不会复制数据库，因为它已经存在。）
为了方便起见，将行注释掉。
最好不要硬编码数据库路径，而最好通过the_context.getDatabasePath(database_name).getPath方法检索它。
因此建议您更改：-
String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;
改为：-
String path = context.getDatabasePath(DBConstant.DATABASE_FILE).getPath();
如 ”-
public class NewpActivity extends AppCompatActivity {
String PaFirstName, PaLastName, PaDOB, PaGender, PaContact, PaStreetAPT, PaCity, PaState, country, PaPincode, PaInsurance;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_newp);
Button signUpBtn = (Button) findViewById(R.id.checkout_btn);
try {
DBOperator.copyDB(this);
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("DB Copy Failed. Issuing runtime exception");
}
signUpBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//Running method for updating string variables from input boxes
//getValues();
//DBOperator.getInstance().execSQL(SQLCommand.NEW_USER, getArgs());
Toast.makeText(getBaseContext(), "Checkout successfully", Toast.LENGTH_SHORT).show();
}
});
//<<<<<<<<<< ADDED TO CONFIRM DATABASE IS AS EXPECTED
DBOperator checkit = DBOperator.getInstance();
Cursor csr = checkit.execQuery("SELECT * FROM sqlite_master");
while (csr.moveToNext()) {
Log.d(
"DBINFO",
"Item with a name of " + csr.getString(csr.getColumnIndex("name")) +
" and a type of " + csr.getString(csr.getColumnIndex("type")) +
" found in the Database."
);
}
}
}
请注意 ，以上示例是如何从表中获取数据并对其进行处理的示例，并且该示例使用了execQuery方法（有效）。
：-
11-12 10:17:01.494 2025-2025/? W/System.err: java.io.FileNotFoundException: fail.db
11-12 10:17:01.494 2025-2025/? W/System.err: at android.content.res.AssetManager.openAsset(Native Method)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.content.res.AssetManager.open(AssetManager.java:315)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.content.res.AssetManager.open(AssetManager.java:289)
11-12 10:17:01.494 2025-2025/? W/System.err: at test.activity.test.DBOperator.copyDB(DBOperator.java:54)
11-12 10:17:01.494 2025-2025/? W/System.err: at test.activity.test.NewpActivity.onCreate(NewpActivity.java:21)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.Activity.performCreate(Activity.java:5008)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.ActivityThread.access$600(ActivityThread.java:130)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.os.Handler.dispatchMessage(Handler.java:99)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.os.Looper.loop(Looper.java:137)
11-12 10:17:01.494 2025-2025/? W/System.err: at android.app.ActivityThread.main(ActivityThread.java:4745)
11-12 10:17:01.494 2025-2025/? W/System.err: at java.lang.reflect.Method.invokeNative(Native Method)
11-12 10:17:01.494 2025-2025/? W/System.err: at java.lang.reflect.Method.invoke(Method.java:511)
11-12 10:17:01.494 2025-2025/? W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-12 10:17:01.494 2025-2025/? W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-12 10:17:01.494 2025-2025/? W/System.err: at dalvik.system.NativeStart.main(Native Method)
11-12 10:17:01.494 2025-2025/? D/AndroidRuntime: Shutting down VM
11-12 10:17:01.494 2025-2025/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xa62a3288)
11-12 10:17:01.494 2025-2025/? E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{test.activity.test/test.activity.test.NewpActivity}: java.lang.RuntimeException: DB Copy Failed. Issuing runtime exception
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: java.lang.RuntimeException: DB Copy Failed. Issuing runtime exception
at test.activity.test.NewpActivity.onCreate(NewpActivity.java:24)
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)
请注意，原始捕获的异常（）和发出的运行时异常有两个异常（您必须具有try / catch，因为copyDB方法会引发异常，因此也可能会引发运行时异常）
：-
11-12 09:59:08.910 1917-1917/test.activity.test D/DBINFO: Item with a name of patient and a type of table found in the Database.
11-12 09:59:08.910 1917-1917/test.activity.test D/DBINFO: Item with a name of android_metadata and a type of table found in the Database.
我还想根据此应用程序中用户功能提供的搜索框值，从数据库中添加检索数据（单击按钮时）。
现在，您应该尝试执行此操作，如果遇到问题，则应该提出一个新问题。 您需要决定如何做。 您要搜索各种列吗？ 您是否希望结果随输入而更改，或者您想单击以启动搜索。 也许某些字段可以使用下拉选择器（微调器），例如，当存在一组特定的值时，例如用于性别。
Android Studio-从SQLite数据库检索数据并插入Spinner
[英]Android Studio - Retrieve Data From SQLite Database and insert into Spinner
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.