Android领域和片段中的空对象引用

Question

我正在寻找我的问题的答案。这是我第一次接触 Realm 数据库，我在保存数据期间遇到片段中的空对象引用问题。有谁知道我做错了什么？

辅助方法：

public void saveTask(final String text, final String date, final String time ) {
    realm.executeTransactionAsync(new Realm.Transaction() {
        @Override
        public void execute(Realm bgRealm) {
            Task task = bgRealm.createObject(Task.class);
            task.setText(text);
            task.setDate(date);
            task.setTime(time);
        }
    }, new Realm.Transaction.OnSuccess() {
        @Override
        public void onSuccess() {
            // Transaction was a success.
            Log.d(TAG, "ON_SUCCESS: Data Written Successfully");
        }
    }, new Realm.Transaction.OnError() {
        @Override
        public void onError(Throwable error) {
            // Transaction failed and was automatically canceled.
            Log.d(TAG, "ON_ERROR: Error");
        }
    });

}

片段中的 OnClick 方法：

@OnClick(R.id.save_button)
public void onClickSave() {

    realmHelper.saveTask(title_text.getText().toString().trim(), date_text.getText().toString().trim(), time_text.getText().toString().trim());
}

onCreateView 内的代码：

    ButterKnife.bind(this, view);

    ((MainActivity) getActivity()).hideFloatingActionButton();

    Realm.init(getActivity());
    RealmConfiguration configuration = new RealmConfiguration
            .Builder()
            .deleteRealmIfMigrationNeeded()
            .build();
    realm = Realm.getInstance(configuration);

我尝试了在 onClick 方法中使用 textview 字段的解决方案，但仍然相同。

Answer 1

从您在片段中的OnClick 方法中，我观察到您有一个领域助手类，您创建了一个名为realmHelper 的实例。由于您正在异步使用领域，我建议您将实例化领域对象传递给辅助方法或在帮助方法或类中重新实例化领域。

将领域实例传递给辅助方法

public void saveTask(Realm realm, final String text, final String date, final String time ) {
    realm.executeTransactionAsync(new Realm.Transaction() {
        @Override
        public void execute(Realm bgRealm) {
            Task task = bgRealm.createObject(Task.class);
            task.setText(text);
            task.setDate(date);
            task.setTime(time);
        }
    }, new Realm.Transaction.OnSuccess() {
        @Override
        public void onSuccess() {
            // Transaction was a success.
            Log.d(TAG, "ON_SUCCESS: Data Written Successfully");
        }
    }, new Realm.Transaction.OnError() {
        @Override
        public void onError(Throwable error) {
            // Transaction failed and was automatically canceled.
            Log.d(TAG, "ON_ERROR: Error");
        }
    });

}

在辅助方法中实例化领域

public void saveTask(Context context, final String text, final String date, final String time ) {
    Realm.init(context);
    RealmConfiguration configuration = new RealmConfiguration
        .Builder()
        .deleteRealmIfMigrationNeeded()
        .build();
    Realm realm = Realm.getInstance(configuration);
    realm.executeTransactionAsync(new Realm.Transaction() {
        @Override
        public void execute(Realm bgRealm) {
            Task task = bgRealm.createObject(Task.class);
            task.setText(text);
            task.setDate(date);
            task.setTime(time);
        }
    }, new Realm.Transaction.OnSuccess() {
        @Override
        public void onSuccess() {
            // Transaction was a success.
            Log.d(TAG, "ON_SUCCESS: Data Written Successfully");
        }
    }, new Realm.Transaction.OnError() {
        @Override
        public void onError(Throwable error) {
            // Transaction failed and was automatically canceled.
            Log.d(TAG, "ON_ERROR: Error");
        }
    });

}