在assests文件夹中的现有sqlite数据库中插入数据，将其删除，检索数据

Question

I have created a sqlite database and placed it in assets folder of my android project. Now i want to perform Insert,Delete,Retrieve operations on this database.

I have created a new activity where i will be entering detail of a person and then i will press save button (checkout_btn) to save that information in existing database.

I do not know what is wrong in this code. I am not getting any error nor even data is getting inserted in existing database.

I also want to add Retrieve data (on button click) from database on basis of a search box value provided by user functionality in this application.

Here is my code:

 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(?,?,?,?,?,?,?,?,?,?)";
}

Answer 1

In the copy db method,you need to close the inputstream after flushing the outpustream.

existing code:

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();**
    }
}

updated code:

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();**
    }
}

Answer 2

Issue 1 - Not calling the DBOperator copyDB method.

You need to call the copyDB method for the Database to be copied from the assets folder. Otherwise an empty database will be created.

This should be done before an attempt is made to get a DBOperator Instance. A convenient place for this call would be immediately after the Activity's ContentView is set eg

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();
            }
        });
    }
}

• Note before running the corrected code you should delete the App's data or uninstall the App so that the database is deleted (otherwise the copyDB method will not copy the database as it exists.)

• Lines commented out for convenience.

Issue 2 - (not an error)

It is much better to not hard code the database path but to retrieve it via the_context.getDatabasePath(database_name).getPath method.

As such it is suggested that you change :-

String path = DBConstant.DATABASE_PATH + "/" + DBConstant.DATABASE_FILE;

to instead be :-

String path = context.getDatabasePath(DBConstant.DATABASE_FILE).getPath();

Additional Stuff

1. At first it might be an idea to confirm that the database contains the expected table(s), adding code (in the Activit's onCreate method after everything else)

such as "-

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."
            );
        }
    }
}

• Note the above is an example of how you can get data from a table and process it and it uses your execQuery method (which works).

  2. Should the database not have been copied to the assets folder and the code above was used then you would get an error along the lines of

:-

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) 

• The failure was forced by changing the database name to fail.db

• Note that there are two exceptions the original caught exception () and then the runtime exception that was issued (you have to have a try/catch as the copyDB method throws an exception so might as well throw a runtime exception)

  3. A good run (that copies the database or doesn't if it already exists) would log the following output (perhaps more if you have more tables or other items wuch an indexes, triggers, views)

:-

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.

I also want to add Retrieve data (on button click) from database on basis of a search box value provided by user functionality in this application.

That you should now try doing, if you have issues then you should ask a new question. You'd need to decide how you would want to do it. Would you want to search on various columns? would you want the results to change as you typed or would you want to a click to initiate the search. Perhaps a drop-down selector (Spinner) could be used for some columns eg say for Gender when there will be a specific set of values.