CODEWITHSUNDEEP
javaandroid
Jackson Vandy
Jackson Vandy

Reputation: 15

Java Android Spinner onItemSelected

The problem Im having is with the onItemSelected method. Whenever I try to change a Views value, Example: TextView, EditView it throws an error.

What Im trying to do is get the when I click on something on the spinner it will display something on the text (anything currently). I hope you can help! Thanks.

Here is my code so you can look at it:

public class MainActivity extends Activity implements OnItemSelectedListener {

    Spinner spinner;
    String[] paths = {"Rectangle", "Circle", "Triangle"};
    String selected;
    Button equals;
    TextView parm1, parm2;
    EditText value1, value2;
    CheckBox checkArea, checkPerm;
    Boolean checkedArea = true, checkedPerm = false;

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

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item, paths);
        spinner = (Spinner) findViewById(R.id.spinner);
        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(this);
    }

    @Override
    public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
            long arg3) {
        int index = arg0.getSelectedItemPosition();

        if(paths[index] == "Rectangle"){
            //Does work
            Toast.makeText(getBaseContext(), "You selected Rectangle", Toast.LENGTH_LONG).show();

            //Doesn't work
            parm1.setText("Hello");
        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {
        // TODO Auto-generated method stub

    }
}

Here is the error that pops up when I run the program. The virtual device will run the program all the way up to when i open it, then it will say Unfortunately *"Programs_name"* has stopped working. Here is the error log:

 02-12 17:26:41.395: D/dalvikvm(1478): GC_FOR_ALLOC freed 45K, 4% free 3331K/3444K, paused 47ms, total 51ms
02-12 17:26:41.985: D/AndroidRuntime(1478): Shutting down VM
02-12 17:26:41.985: W/dalvikvm(1478): threadid=1: thread exiting with uncaught exception (group=0xb1aadba8)
02-12 17:26:41.995: E/AndroidRuntime(1478): FATAL EXCEPTION: main
02-12 17:26:41.995: E/AndroidRuntime(1478): Process: com.example.gcfcalculator, PID: 1478
02-12 17:26:41.995: E/AndroidRuntime(1478): java.lang.NullPointerException
02-12 17:26:41.995: E/AndroidRuntime(1478):     at com.example.gcfcalculator.MainActivity.onItemSelected(MainActivity.java:53)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.widget.AdapterView.fireOnSelected(AdapterView.java:893)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.widget.AdapterView.access$200(AdapterView.java:48)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:861)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.os.Handler.handleCallback(Handler.java:733)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.os.Handler.dispatchMessage(Handler.java:95)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.os.Looper.loop(Looper.java:136)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at android.app.ActivityThread.main(ActivityThread.java:5017)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at java.lang.reflect.Method.invokeNative(Native Method)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at java.lang.reflect.Method.invoke(Method.java:515)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-12 17:26:41.995: E/AndroidRuntime(1478):     at dalvik.system.NativeStart.main(Native Method)
02-12 17:26:47.055: I/Process(1478): Sending signal. PID: 1478 SIG: 9

Upvotes: 0

Views: 1030

Answers (1)

Martin Cazares
Martin Cazares

Reputation: 13705

You have no reference to the TextView parm1, to get a reference you must first call findViewById as follows:

parm1 = (TextView) findViewById(R.id.yourId);

Until you do that, you will be able to use that textView, also, when comparing Strings do not use == instead go for Object.equal(), and just as a small useful tip, if you have a literal string instead of doing

paths[index].equals("Rectangle")

do

"Rectangle".equals(paths[index])

This way you have an extra validation for null pointer exception, because your literal could never be null, however theres a chance that "paths[index]" might be null

Hope it Helps!

Regards!

Upvotes: 1

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