Question

我正在实现一个onListItemClick方法，我得到IndexOutofBoundsException：

java.lang.IndexOutOfBoundsException: Index: 4, Size: 0
                                                                       at java.util.ArrayList.get(ArrayList.java:411)
                                                                       at com.lalosoft.roomdemo.MainActivity.onListItemClick(MainActivity.java:91)
                                                                       at com.lalosoft.roomdemo.ProductAdapter$ProductViewHolder.onClick(ProductAdapter.java:114)
                                                                       at android.view.View.performClick(View.java:5647)
                                                                       at android.view.View$PerformClick.run(View.java:22465)
                                                                       at android.os.Handler.handleCallback(Handler.java:761)
                                                                       at android.os.Handler.dispatchMessage(Handler.java:98)
                                                                       at android.os.Looper.loop(Looper.java:156)
                                                                       at android.app.ActivityThread.main(ActivityThread.java:6577)
                                                                       at java.lang.reflect.Method.invoke(Native Method)
                                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:941)
                                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:831)

我的MainActivity代码是：

 public class MainActivity extends AppCompatActivity implements
        ProductAdapter.ListItemClickListener {

    private RecyclerView recyclerView;
    private Toast mToast;
    List<Pelates> pelates;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    recyclerView = (RecyclerView) findViewById(R.id.recycler_view);

    // run the sentence in a new thread
    new Thread(new Runnable() {
        @Override
        public void run() {
            pelates = App.get().getDB().productDao().getAll();
            boolean force = App.get().isForceUpdate();
            if (force || pelates.isEmpty()) {
                retrieveProducts();
            } else {
                populateProducts(pelates);
            }
        }
    }).start();

}


@Override
public void onListItemClick(int clickedItemIndex) {

    String toastMessage = "Item #" + clickedItemIndex + " name= "+ pelates.get(clickedItemIndex).getName();
    mToast = Toast.makeText(this, toastMessage, Toast.LENGTH_SHORT);
    mToast.show();
}

private void retrieveProducts() {
    List<Pelates> list = new ArrayList<>();

    String names[] = {"Νεκτάριος", "Giannis", "Kostas", "Panagiotis", "Athina", "Maria", "Αντωνία"};
    String surnames[] = {"Κοντολαιμάκης", "Papadak", "Androulak", "Iliopoulos", "Kouts", "Ioannidou", "Ιωακειμίδου"};
    int arxikoPoso[] = {500, 3000, 5000, 4500, 10000, 1000, 100};

    for (int i = 0; i < 7; i++) {
        Pelates pelates = new Pelates();
        pelates.setName(names[i]);
        pelates.setSurname(surnames[i]);
        pelates.setArxiko_poso(arxikoPoso[i]);
        pelates.setImageUrl("http://lorempixel.com/500/500/technics/" + i);
        list.add(pelates);
    }

    // insert product list into database
    App.get().getDB().productDao().insertAll(list);

    // disable flag for force update
    App.get().setForceUpdate(false);

    populateProducts(list);
}

private void populateProducts(final List<Pelates> pelates) {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            recyclerView.setAdapter(new ProductAdapter(pelates, MainActivity.this));
        }
    });
}

}

我在第一次我得到IndexOutOfBoundsException 我在以下代码行运行我的应用程序：

String toastMessage = "Item #" + clickedItemIndex + " name= "+ pelates.get(clickedItemIndex).getName();

第一次之后我没有得到任何错误。我正在使用Room数据库，并且只在我第一次运行应用程序时才使用数据填充数据库。

我试着看到pelates的大小，但它是零。为什么呢？

Answer 1

您应该在List<Pelates> pelates;内填充retrieveProducts()，而不是创建新列表。

List上的Android IndexOutOfBoundsException错误

1 个答案: