MVP和RxJava-處理Android上的方向更改

Question

我使用的MVP和RxJava與google-samples回購類似。

我想問一下如何正確處理屏幕方向變化。

Answer 1

還有一種策略可以保存演示者狀態和Observable的狀態： 保留Fragment 。 這樣，您就省去了將數據保存到Bundle標准Android方法（該方法只能保存簡單變量，而不能保存網絡請求的狀態。）

Activity ：

public class MainActivity extends AppCompatActivity implements MainActivityView {
    private static final String TAG_RETAIN_FRAGMENT = "retain_fragment";

    MainActivityPresenter mPresenter;

    private MainActivityRetainFragment mRetainFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        initRetainFragment();
        initPresenter();
    }

    private void initRetainFragment() {
        FragmentManager fm = getSupportFragmentManager();
        mRetainFragment = (MainActivityRetainFragment) fm.findFragmentByTag(TAG_RETAIN_FRAGMENT);
        if (mRetainFragment == null) {
            mRetainFragment = new MainActivityRetainFragment();
            fm.beginTransaction().add(mRetainFragment, TAG_RETAIN_FRAGMENT).commit();
        }
    }

    private void initPresenter() {
        mPresenter = mRetainFragment.getPresenter();
        mRetainFragment.retainPresenter(null);
        if (mPresenter == null) {
            mPresenter = new MainActivityPresenter();
        }
        mPresenter.attachView(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (!isFinishing()) {
            mRetainFragment.retainPresenter(mPresenter);
            return;
        }
        mPresenter.detachView();
        mPresenter = null;
    }
}

保留Fragment ：

public class MainActivityRetainFragment extends Fragment {
    private MainActivityPresenter presenter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    public void retainPresenter(MainActivityPresenter presenter) {
        this.presenter = presenter;
    }

    public MainActivityPresenter getPresenter() {
        return presenter;
    }
}

注意活動生命周期事件的處理方式。 創建Activity ，將保留Fragment添加到后堆棧，並在生命周期事件中將其從后堆棧恢復。 keep Fragment沒有任何視圖，它只是配置更改過程中演示者的持有人。 請注意主要的調用，該調用可以從堆棧中恢復完全相同的片段（及其內容）：

setRetainInstance(true)

如果您擔心內存泄漏：每次還原演示者時，都會還原演示者的視圖：

mPresenter.attachView(this);

因此，以前的“ Activity引用將被新的“ Activity引用替代。

在這里了解有關配置更改的更多信息

Answer 2

我通過將視圖的狀態封裝在presenter中的特定ViewState類中來進行處理，並且很容易測試。

public interface BaseViewState {
    void saveState(@NonNull Bundle outState);

    void restoreState(@Nullable Bundle savedInstanceState);
}

class HomeViewState implements BaseViewState {

    static final long NONE_NUM = -1;

    static final String STATE_COMIC_NUM = "state_comic_num";

    private long comicNum = NONE_NUM;

    @Inject
    HomeViewState() {
    }

    @Override
    public void saveState(@NonNull Bundle outState) {
        outState.putLong(STATE_COMIC_NUM, comicNum);
    }

    @Override
    public void restoreState(@Nullable Bundle savedInstanceState) {
        if (savedInstanceState != null) {
            comicNum = savedInstanceState.getLong(STATE_COMIC_NUM, NONE_NUM);
        }
    }

    long getComicNumber() {
        return comicNum;
    }

    void setComicNum(long comicNum) {
        this.comicNum = comicNum;
    }
}

從演示者的viewState獲取/設置值，這有助於保持其更新以及演示者無狀態。

public class HomePresenter implements HomeContract.Presenter {

    private HomeViewState viewState;

    HomeViewState getViewState() {
        return viewState;
    }

    @Override
    public void loadComic() {
       loadComic(viewState.getComicNumber());
    }
    ...
}

在“活動為視圖”中應啟動保存和還原的調用。

public class MainActivity extends BaseActivity implements HomeContract.View {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            ...
            homePresenter.getViewState().restoreState(savedInstanceState);
        }


        @Override
        public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
            super.onSaveInstanceState(outState, outPersistentState);

            homePresenter.getViewState().saveState(outState);
        }
     ...
}