The value of QR Code Scanner cannot show on new activity

Issue

I am trying to make a simple QR Code scanner and run well if the result shows in the MainActivity. But when I'm trying to generate new Activity as a result, it can't show. Would you like to help me with this problem? Thank you.

Here is the result of the scanner code in the scanner.java:

@Override
    public void handleResult(Result rawResult) {
        startActivity(new Intent(getApplicationContext(),ResultActivity.class));
        ResultActivity.scanText2.setText(rawResult.getText());
        onBackPressed(); 

    }

And here is the code of my new Activity for showing the result:

public class ResultActivity extends AppCompatActivity {
    public static TextView scanText2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_patient);

        scanText2 = (TextView) findViewById(R.id.scanText2);
    }
}

Solution

There are a lot of issues with this:

1. You are launching PatientActivity, not ResultActivity in handleResult()
2. You are trying to set the value of a TextView in another Activity with this code: ResultActivity.scanText2.setText(rawResult.getText());

This is an absolute no-no. Pass the data to ResultActivity as an Intent extra when you launch it. You cannot access the views of another Activity like that.

3. You expect that ResultActivity.scanText2 will contain a reference to a TextView, but at this point it will only contain null. The reason is that it takes some time for ResultActivity to actually start and call its onCreate(). You have not accounted for this timing in your code. To solve this problem, just see (2) above.

Also, you should have gotten a bunch of crashes with useful messages in your logcat. In the future please look there to solve problems and/or post the messages with stacktrace in your Stackoverflow questions.

Answered By - David Wasser