androidmultithreadingsqlitehandler
How to insert a row into SQLite on a different thread and return the result using handler?
I have this SQLite DatabaseHelper operation that inserts a row into the local database. I want to do this on a different thread and use handler to take the result back to the UI Thread. How can I do this? Here is the operation:
public void insertEmployee(String employeeType, String employeeName, Double employeeConvRate, String employeeDesc) {
new Thread(() -> {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(EXPENSE_C_TYPE, employeeType);
values.put(EXPENSE_C_NAME, employeeName);
values.put(EXPENSE_C_CR, employeeConvRate);
values.put(EXPENSE_C_DESC, employeeDesc);
long id = db.insert(EXPENSE_TABLE_NAME, null, values);
db.close();
}).start();
}
Usually this function is a public long that returns the id variable.
EDIT - HOW I DID IT:
I created this interface with generic parameter:
public interface OnDatabaseResult<T> {
void onResult(T result);
}
Then I aded the handler inside the database operation:
public void insertEmployee(String employeeType, String employeeName, Double employeeConvRate, String employeeDesc) {
new Thread(() -> {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(EXPENSE_C_TYPE, employeeType);
values.put(EXPENSE_C_NAME, employeeName);
values.put(EXPENSE_C_CR, employeeConvRate);
values.put(EXPENSE_C_DESC, employeeDesc);
long id = db.insert(EXPENSE_TABLE_NAME, null, values);
db.close();
handler.post(()) -> onDatabaseResult.onResult(id)
}).start();
}
Then in main activity I added the function that creates the row:
public void createEmploye(String employeeType, String employeeName, Double employeeConvRate, String employeeDesc){
DatabaseHelper databaseHelper = new DatabaseHelper(this);
databaseHelper.insertEmployee(type, name, rate, desc, new OnDatabaseResult<Long>(){
@Override
public void onResult(Long result){
Employee employee = databaseHelper.getEmployee(result);
if(employee!=null){
employeeList.add(o, employee);
employeeAdapter.notifyDataSetChanged();
}
}
});
}
And now it works flawlessly.
Solution
You can use an Interface.
The following is an example based upon your code, that inserts an Expense row (albeit the same row but with a different id) on another thread and displays the inserted id.
The interface MyInterface.java is simply :-
public interface MyInterface {
void changeID(long newid);
}
The Database Helper DatabaseHelper.java is :-
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DBNAME = "mydb";
public static final int DBVERSION = 1;
public static final String EXPENSE_TABLE_NAME = "expense";
public static final String EXPENSE_C_ID = BaseColumns._ID;
public static final String EXPENSE_C_TYPE = "type";
public static final String EXPENSE_C_NAME = "name";
public static final String EXPENSE_C_CR = "cr";
public static final String EXPENSE_C_DESC = "description";
public DatabaseHelper(Context context) {
super(context, DBNAME, null, DBVERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS " + EXPENSE_TABLE_NAME + "(" +
EXPENSE_C_ID + " INTEGER PRIMARY KEY, " +
EXPENSE_C_TYPE + " TEXT, " +
EXPENSE_C_NAME + " TEXT," +
EXPENSE_C_CR + " REAL, " +
EXPENSE_C_DESC + " TEXT" +
")");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public long insertEmployee(String employeeType, String employeeName, Double employeeConvRate, String employeeDesc) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(EXPENSE_C_TYPE, employeeType);
values.put(EXPENSE_C_NAME, employeeName);
values.put(EXPENSE_C_CR, employeeConvRate);
values.put(EXPENSE_C_DESC, employeeDesc);
long id = db.insert(EXPENSE_TABLE_NAME, null, values);
db.close();
return id;
}
}
- Note that the insertEmployee method is not specifically run in another thread (it is thus more flexible).
The layout for the activity, activity_main.xml is very simple a TextView for displaying the id (initially set to Hello World) and has a button that when clicked inserts the new row:-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="@+id/result"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!" />
<Button
android:id="@+id/doit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="DO IT"/>
</LinearLayout>
Finally MainActivity.java :-
public class MainActivity extends AppCompatActivity implements MyInterface {
TextView mShowResult; // TextView to display the latest id (initially Hello World)
Button mDoIt; // The Button, when clicked inserts a new row
DatabaseHelper mDBHlpr; // The Database Helper
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mShowResult = this.findViewById(R.id.result); // Get the TextView for the dispaly
mDoIt = this.findViewById(R.id.doit); // Get the Button
mDBHlpr = new DatabaseHelper(this); // Instantiate the Database Helper
// Set the Buttons onClick Listener
mDoIt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doItInAnotherThread("Full time", "Fred",32.897,"Worker"); //<<<<<<<<<<<
}
});
}
/**
* As MainActivity implements MyInterface which has the changeID template
* the changeID method must be implemented. This will be called when the doItInAnotherThread calls
* changeID(?).
*
* As this is updating a view then it must be run on the UI thread
*/
public void changeID(final long newid) {
runOnUiThread(new Runnable() {
@Override
public void run() {
mShowResult.setText(String.valueOf(newid));
}
});
}
/**
* Do the work in another thread returning changed id via the interface MyInterface
*/
private void doItInAnotherThread(final String employeeType, final String employeeName, final Double employeeConvRate, final String employeeDesc) {
new Thread(new Runnable() {
@Override
public void run() {
long id = mDBHlpr.insertEmployee(employeeType, employeeName, employeeConvRate, employeeDesc);
changeID(id);
}
}).start();
}
}
Results
1. When first run :-
2. When the DO IT button is clicked (instead of Hello World the display shows 1)
