Question

我通过覆盖活动中的ArrayList来保存onSaveInstanceState个对象。在该活动的onCreate方法中，我恢复了我保存的对象列表。

以下是活动的代码 -

public class MovieListActivity extends AppCompatActivity {

private EndlessRecyclerViewScrollListener scrollListener;
private ArrayList<Movie> movies;
private MovieListAdapter movieListAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_movie_list);
    RecyclerView moviesRecyclerView = (RecyclerView) findViewById(R.id.movie_list_rv);

    if (savedInstanceState == null || !savedInstanceState.containsKey("movieList")) {
        movies = createMovies(30);
    } else {
        // Restoring only the list of movies not the scroll position
        movies = savedInstanceState.getParcelableArrayList("movieList");
    }

    movieListAdapter = new MovieListAdapter(this, movies);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);

    moviesRecyclerView.setAdapter(movieListAdapter);
    moviesRecyclerView.setLayoutManager(layoutManager);

    scrollListener = new EndlessRecyclerViewScrollListener(layoutManager) {
        @Override
        public void onLoadMore(int page, final int totalItemsCount, RecyclerView view) {
            Handler handler = new Handler();
            final Runnable r = new Runnable() {
                public void run() {
                    movies.addAll(createMovies(20));
                    movieListAdapter.notifyItemRangeInserted(totalItemsCount, movies.size() - 1);
                }
            };
            handler.post(r);
        }
    };
    moviesRecyclerView.addOnScrollListener(scrollListener);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    // Saving only the list of movies
    outState.putParcelableArrayList("movieList", movies);
    super.onSaveInstanceState(outState);
}

private ArrayList<Movie> createMovies(int numberOfMovies) {
    ArrayList<Movie> movieList = new ArrayList<>();
    for(int i=0; i<numberOfMovies; i++) {
        movieList.add(new Movie("Hello", new DateTime("2017-03-16T01:20"), "This is a very good movie"));
    }
    Log.i("Create", "create called");
    return movieList;
}

}

当我旋转屏幕时，不仅会恢复对象，还会恢复滚动位置。

即使我没有保存，滚动位置如何保存和恢复？
调用super.onCreate(savedInstanceState)时是否自动保存滚动位置？

旋转之前和之后模拟器的屏幕截图 - 旋转之前

＆安培;旋转后

感谢您的帮助！

Answer 1

当您的活动开始停止时，系统会调用onSaveInstanceState（）方法，以便您的活动可以使用一组键值对保存状态信息。此方法的默认实现保存有关活动视图层次结构状态的瞬态信息，例如EditText小部件中的文本或ListView小部件的滚动位置

有关详细信息，请参阅https://developer.android.com/guide/components/activities/activity-lifecycle.html

中的保存和恢复活动状态

旋转屏幕时如何保存滚动位置？

1 个答案: