SQlite dataabase operation and AsyncTask

Question

I am learning AsyncTask class and with following example to practice. I have a UI that have a EditText (for data entry), a radiogroup with 5 radiobuttons, and a button (submit). The idea is that when user select the radiobutton and enter a value to EDITTEXT. Following button click, the information will go to the database table. The database table is created and the whole code works. But I would like to run the database operation function in the background with AsyncTask. something goes wrong after applying AsyncTask class. Please help me.

here is the code works without AsyncTask:

    package jhapps.com.myspending;

    import android.os.Bundle;
    import android.support.design.widget.FloatingActionButton;
    import android.support.design.widget.Snackbar;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.RadioButton;
    import android.widget.RadioGroup;
    import android.widget.Toast;

    public class Child extends AppCompatActivity {

private static Button btnsubmit;
private static RadioGroup rgChild;
private static RadioButton rbChild;
private static EditText dollarAmount;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_child);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    DataSubmitChild();
}

private void DataSubmitChild(){
    btnsubmit=(Button)findViewById(R.id.btnSubmitChild);
    btnsubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            rgChild = (RadioGroup) findViewById(R.id.rgChildren);
            int selectedRbChild = rgChild.getCheckedRadioButtonId();
            rbChild = (RadioButton) findViewById(selectedRbChild);
            String rbChildF = rbChild.getText().toString();



            dollarAmount = (EditText) findViewById(R.id.amountEnterChild);
            String dollarAmountF = dollarAmount.getText().toString();
            float dollarAmountFloat = Float.parseFloat(dollarAmountF);





        DataBaseHelper dataBaseHelper = new DataBaseHelper(Child.this);

        if (dollarAmountFloat != 0 & rbChildF != "") {
            int itemID;

            switch (rbChildF) {
                case "Daycare":itemID=53;
                    dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                    break;
                case "Lessons and Activities": itemID=54;
                    dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                    break;
                case "Allowance":itemID=55;
                    dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                    break;
                case "School Supplies and Fees" :itemID=56;
                    dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                    break;
                case "Babysitting":itemID=57;
                    dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                    break;

            }
            Toast.makeText(Child.this,"Your spending is recorded!",Toast.LENGTH_LONG).show();

            dollarAmount.setText("");
            rgChild.clearCheck();
        }else
            Toast.makeText(Child.this,"Please choose an Item",Toast.LENGTH_LONG).show();
        }

    });


    }

}

here is the code with AsyncTask that did not work:

    package jhapps.com.myspending;

    import android.content.Context;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.support.design.widget.FloatingActionButton;
    import android.support.design.widget.Snackbar;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.RadioButton;
    import android.widget.RadioGroup;
    import android.widget.Toast;

    public class Child extends AppCompatActivity {
private static Button btnsubmit;
private static RadioGroup rgChild;
private static RadioButton rbChild;
private  EditText dollarAmount;

Context ctx;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_child);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    //DataSubmitChild();
    rgChild = (RadioGroup) findViewById(R.id.rgChildren);
    int selectedRbChild = rgChild.getCheckedRadioButtonId();
    rbChild = (RadioButton) findViewById(selectedRbChild);

    dollarAmount = (EditText) findViewById(R.id.amountEnterChild);



    btnsubmit=(Button)findViewById(R.id.btnSubmitChild);
    btnsubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            BackgroundTask backgroundTask=new BackgroundTask();
            backgroundTask.execute();
        }
    });
    dollarAmount.setText("");
    rgChild.clearCheck();
}
    private class BackgroundTask extends AsyncTask<Void,Void,Void>{
String rbChildF = rbChild.getText().toString();
String dollarAmountF = dollarAmount.getText().toString();
float dollarAmountFloat = Float.parseFloat(dollarAmountF);

@Override
protected Void doInBackground(Void... params) {


    DataBaseHelper dataBaseHelper = new DataBaseHelper(getBaseContext());

            if (dollarAmountFloat != 0 & rbChildF != "") {
                int itemID;

                switch (rbChildF) {
                    case "Daycare":itemID=53;
                        dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                        break;
                    case "Lessons and Activities": itemID=54;
                        dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                        break;
                    case "Allowance":itemID=55;
                        dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                        break;
                    case "School Supplies and Fees" :itemID=56;
                        dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                        break;
                    case "Babysitting":itemID=57;
                        dataBaseHelper.insertDataSpending(itemID, dollarAmountFloat);
                        break;

                }
                Toast.makeText(Child.this,"Your spending is recorded!",Toast.LENGTH_LONG).show();


            }else
                Toast.makeText(Child.this,"Please choose an Item",Toast.LENGTH_LONG).show();

    return null;
}

} }

here is the error message:

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: jhapps.com.myspending, PID: 27613
              java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.RadioButton.getText()' on a null object reference
                  at jhapps.com.myspending.Child$BackgroundTask.<init>(Child.java:62)
                  at jhapps.com.myspending.Child$BackgroundTask.<init>(Child.java:0)
                  at jhapps.com.myspending.Child$2.onClick(Child.java:54)
                  at android.view.View.performClick(View.java:5198)
                  at android.view.View$PerformClick.run(View.java:21147)
                  at android.os.Handler.handleCallback(Handler.java:739)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

score 1 · Accepted Answer · answered Nov 11 '16 at 20:27

These views are all null...

private class BackgroundTask extends AsyncTask<Void,Void,Void>{

    // Don't put these here...
    String rbChildF = rbChild.getText().toString();
    String dollarAmountF = dollarAmount.getText().toString();
    float dollarAmountFloat = Float.parseFloat(dollarAmountF);

If you really need those values, then make a constructor

private class BackgroundTask extends AsyncTask<Void,Void,Void>{

    String rbChildF, dollarAmountF;
    float dollarAmount;

    public BackgroundTask(String radio, String dollarAmtF, float dollars) {
        this.rbChildF = radio;
        this.dollarAmountF = dollarAmtF;
        this.dollarAmount = dollars;
    }

And pass those values in

    String rbChildF = rbChild.getText().toString();
    String dollarAmountF = dollarAmount.getText().toString();
    float dollarAmountFloat = Float.parseFloat(dollarAmountF);

    new BackgroundTask(rbChildF, dollarAmountF, dollarAmountFloat).execute();

many many thanks!! This is a great help! It helps me understand the concept a lot. — J Huang, Nov 11 '16 at 20:57

Najib Maddah · Answer 2 · 2016-11-11T21:11:50.667

0

Man the asyctask is an independent script block it isn't aware of your views values. To make the asynctask aware of your views edittext or radio values u should pass the parent view to the asyctask constructor. Than in the constructor body use findviewbyid to retrieve the values that will be used in the doinbackground method.

Remember. The constructor and the onpostexecute are executed on the main thread. The asyctask consist in what happen in doinbackground.

edited Nov 11 '16 at 21:11

answered Nov 11 '16 at 20:48

Najib Maddah

56
3

Thank you for the concept. It help me to understand the class and android in general. – J Huang Nov 11 '16 at 21:07

SQlite dataabase operation and AsyncTask

2 Answers2