java - Android Spinner 上的 IndexOutOfBoundException

Question

我正在制作一个将单位转换为不同单位的应用程序。我正在尝试使该应用程序在以下步骤中运行。

1. 选择带有旋转器的类别(温度、长度等)
2. 根据选择的类别，其他两个旋转器将显示属于每个类别的单位。

这是到目前为止的代码。

public class UnitConverterFragment extends Fragment implements AdapterView.OnItemSelectedListener {
    private EditText etValue;
    private Spinner spCategory, spFrom, spTo;
    private UnitConverter currentConverter, lastConverter;
    private ArrayAdapter<String> categoryArrayAdapter;
    private ArrayAdapter<CharSequence> unitArrayAdapter;
    private String unitFrom, unitTo;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_unitconverter, container, false);
        spCategory = (Spinner) view.findViewById(R.id.spCategory);
        spFrom = (Spinner) view.findViewById(R.id.spFrom);
        spTo = (Spinner) view.findViewById(R.id.spTo);
        etValue = (EditText) view.findViewById(R.id.etValue);

        spCategory.setOnItemSelectedListener(this);
        spFrom.setOnItemSelectedListener(this);
        spTo.setOnItemSelectedListener(this);

        categoryArrayAdapter = new ArrayAdapter<>(view.getContext(), android.R.layout.simple_spinner_dropdown_item, getResources().getStringArray(R.array.category));
        categoryArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spCategory.setAdapter(categoryArrayAdapter);
        categoryArrayAdapter.setNotifyOnChange(true);

        unitArrayAdapter = new ArrayAdapter<>(view.getContext(), android.R.layout.simple_spinner_item);
        unitArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spFrom.setAdapter(unitArrayAdapter);
        spTo.setAdapter(unitArrayAdapter);

        unitArrayAdapter.setNotifyOnChange(true);

        currentConverter = new TemperatureConverter();
        lastConverter = currentConverter;

        return view;
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

        if(view.getParent() == spCategory) {
            switch(position) {
                case 0:
                    setConverter(new TemperatureConverter());
                    break;
                case 1:
                    setConverter(new LengthConverter());
                    break;
                case 2:
                    setConverter(new MassConverter());
                    break;
                case 3:
                    setConverter(new SpeedConverter());
                    break;
                case 4:
                    setConverter(new VolumeConverter());
                    break;
                case 5:
                    setConverter(new AreaConverter());
                    break;
                case 6:
                    setConverter(new FuelConsumptionConverter());
                    break;
                case 7:
                    setConverter(new TimeConverter());
                    break;
                case 8:
                    setConverter(new DigitalStorageConverter());
                    break;
            }

            fillFromToSpinner(position);

            spFrom.setSelection(0);
            spTo.setSelection(0);

            **unitFrom = spFrom.getItemAtPosition(0).toString();
            unitTo = spTo.getItemAtPosition(0).toString();**

        } else if(view.getParent() == spFrom) {
            unitFrom = spFrom.getSelectedItem().toString();
        } else if(view.getParent() == spTo) {
            unitTo = spTo.getSelectedItem().toString();
        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }

    private void setConverter(UnitConverter converter) {
        lastConverter = currentConverter;
        currentConverter = converter;

        lastConverter = null;
    }

    private void fillFromToSpinner(int position) {
        switch(position) {
            case 0:
                fillSpinnerWithTemperatureUnits();
                break;
            case 1:
                fillSpinnerWithLengthUnits();
                break;
            case 2:
                fillSpinnerWithMassUnits();
                break;
            case 3:
                fillSpinnerWithSpeedUnits();
                break;
            case 4:
                fillSpinnerWithVolumeUnits();
                break;
            case 5:
                fillSpinnerWithAreaUnits();
                break;
            case 6:
                fillSpinnerWithFuelConsumptionUnits();
                break;
            case 7:
                fillSpinnerWithTimeUnits();
                break;
            case 8:
                fillSpinnerWithDigitalStorageUnits();
                break;
        }
    }

    private void fillSpinnerWithTemperatureUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.temperature, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithLengthUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.length, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithMassUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.mass, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();

    }

    private void fillSpinnerWithSpeedUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.speed, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithVolumeUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.volume, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithAreaUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.area, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithFuelConsumptionUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.fuel_consumption, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithTimeUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.time, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }

    private void fillSpinnerWithDigitalStorageUnits() {
        unitArrayAdapter.clear();
        unitArrayAdapter.createFromResource(getView().getContext(), R.array.digital_storage, android.R.layout.simple_spinner_item);
        unitArrayAdapter.notifyDataSetChanged();
    }
}

运行应用程序时，它突然死机，并在突出显示的部分显示 IndexOutOfBoundException。

仅供引用，这是日志。

java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
            at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
            at java.util.ArrayList.get(ArrayList.java:308)
            at android.widget.ArrayAdapter.getItem(ArrayAdapter.java:337)
            at android.widget.AdapterView.getItemAtPosition(AdapterView.java:831)
            at com.marshall.calculator.ui.UnitConverterFragment.onItemSelected(UnitConverterFragment.java:102)
            at android.widget.AdapterView.fireOnSelected(AdapterView.java:964)
            at android.widget.AdapterView.access$200(AdapterView.java:49)
            at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:928)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5602)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

任何解决此问题的建议都将非常感激。

Answer 1

已更新在你的unitArrayAdapter中你没有传递任何数组字符串它是 null ，将其更改为此

private static final String[] items={"lorem", "ipsum", "dolor","sit", "amet","consectetuer", };

unitArrayAdapter = new ArrayAdapter<>(view.getContext(), android.R.layout.simple_spinner_item, items);