将ArrayList<Model>从Activity传递到Fragment的Android操作

Question

你好，我想将数据ArrayList<Division>发送到片段类ListContentFragment。

在MainActivity中，我正在进行网络调用以获取数据（JSON），然后解析它以创建ArrayList<Division>，现在我想用接收到的数据（现在在ArrayList<Division>中）填充列表视图。

MainActivity

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Adding Toolbar to Main screen
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Setting ViewPager for each Tabs
        ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);
        // Set Tabs inside Toolbar
        TabLayout tabs = (TabLayout) findViewById(R.id.tabs);
        tabs.setupWithViewPager(viewPager);
        // Create Navigation drawer and inlfate layout
        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer);
        // Adding menu icon to Toolbar
        ActionBar supportActionBar = getSupportActionBar();
        if (supportActionBar != null) {
            VectorDrawableCompat indicator
                    = VectorDrawableCompat.create(getResources(), R.drawable.ic_menu, getTheme());
            indicator.setTint(ResourcesCompat.getColor(getResources(),R.color.white,getTheme()));
            supportActionBar.setHomeAsUpIndicator(indicator);
            supportActionBar.setDisplayHomeAsUpEnabled(true);
        }
        // Set behavior of Navigation drawer
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    // This method will trigger on item Click of navigation menu
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        // Set item in checked state
                        menuItem.setChecked(true);

                        // TODO: handle navigation
                        Toast.makeText(MainActivity.this, "Clicked: " + menuItem.getTitle(), Toast.LENGTH_SHORT).show();

                        // Closing drawer on item click
                        mDrawerLayout.closeDrawers();
                        return true;
                    }
                });
        // Adding Floating Action Button to bottom right of main view
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Snackbar.make(v, "Hello Snackbar!",
                        Snackbar.LENGTH_LONG).show();
            }
        });

        // Network request test with volley
        NetworkRequests networkRequest = new NetworkRequests(this);
        networkRequest.fetchDummyData();
        divisionList = networkRequest.getDivisions();
    }

    // Add Fragments to Tabs
    private void setupViewPager(ViewPager viewPager) {
        Adapter adapter = new Adapter(getSupportFragmentManager());
        adapter.addFragment(new ListContentFragment(), "List");
        adapter.addFragment(new TileContentFragment(), "Tile");
        adapter.addFragment(new CardContentFragment(), "Card");
        viewPager.setAdapter(adapter);
    }

片段（目前是硬编码的，希望使用ArrayList填充）

public class ListContentFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        RecyclerView recyclerView = (RecyclerView) inflater.inflate(
                R.layout.recycler_view, container, false);
        ContentAdapter adapter = new ContentAdapter(recyclerView.getContext());
        recyclerView.setAdapter(adapter);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        return recyclerView;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public ImageView avator;
        public TextView name;
        public TextView description;
        public ViewHolder(LayoutInflater inflater, ViewGroup parent) {
            super(inflater.inflate(R.layout.item_list, parent, false));
            avator = (ImageView) itemView.findViewById(R.id.list_avatar);
            name = (TextView) itemView.findViewById(R.id.list_title);
            description = (TextView) itemView.findViewById(R.id.list_desc);
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Context context = v.getContext();
                    Intent intent = new Intent(context, DetailActivity.class);
                    intent.putExtra(DetailActivity.EXTRA_POSITION, getAdapterPosition());
                    context.startActivity(intent);
                }
            });
        }
    }

    /**
     * Adapter to display recycler view.
     */
    public static class ContentAdapter extends RecyclerView.Adapter<ViewHolder> {
        // Set numbers of List in RecyclerView.
        private static final int LENGTH = 18;

        private final String[] mPlaces;
        private final String[] mPlaceDesc;
        private final Drawable[] mPlaceAvators;

        public ContentAdapter(Context context) {
            Resources resources = context.getResources();
            mPlaces = resources.getStringArray(R.array.places);
            mPlaceDesc = resources.getStringArray(R.array.place_desc);
            TypedArray a = resources.obtainTypedArray(R.array.place_avator);
            mPlaceAvators = new Drawable[a.length()];
            for (int i = 0; i < mPlaceAvators.length; i++) {
                mPlaceAvators[i] = a.getDrawable(i);
            }
            a.recycle();
        }
        @Override
        public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            return new ViewHolder(LayoutInflater.from(parent.getContext()), parent);
        }

        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            holder.avator.setImageDrawable(mPlaceAvators[position % mPlaceAvators.length]);
            holder.name.setText(mPlaces[position % mPlaces.length]);
            holder.description.setText(mPlaceDesc[position % mPlaceDesc.length]);
        }

        @Override
        public int getItemCount() {
            return LENGTH;
        }
    }

}

- user986508

Answer 1

如果您想将ArrayList传递给您的片段，则需要确保Model类实现了Parcelable。下面是一个示例：

public class ObjectName implements Parcelable {


    public ObjectName(Parcel in) {
        super();
        readFromParcel(in);
    }

    public static final Parcelable.Creator<ObjectName> CREATOR = new Parcelable.Creator<ObjectName>() {
        public ObjectName createFromParcel(Parcel in) {
            return new ObjectName(in);
        }

        public ObjectName[] newArray(int size) {

            return new ObjectName[size];
        }

    };

    public void readFromParcel(Parcel in) {
        Value1 = in.readInt();
        Value2 = in.readInt();
        Value3 = in.readInt();

    }

    public int describeContents() {
        return 0;
    }

    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(Value1);
        dest.writeInt(Value2);
        dest.writeInt(Value3);
    }
}

那么您可以将ArrayList<ObjectName>添加到Bundle对象中。

ArrayList<ObjectName> arraylist = new Arraylist<ObjectName>();  
Bundle bundle = new Bundle();  
bundle.putParcelableArrayList("arraylist", arraylist);
fragment.setArguments(bundle);

之后，您可以使用以下方法获取此数据：

Bundle extras = getIntent().getExtras();  
ArrayList<ObjectName> arraylist  = extras.getParcelableArrayList("arraylist");

最后，您可以在片段中显示这些数据的列表。希望这能帮助您得到您期望的答案。

- Alex Chengalan

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谢谢Alex，我会实现这个。 - user986508

Answer 2

我也曾遇到同样的问题。 你可以尝试这个方法。 不要将arraylist作为bundle发送到fragment中，而是在activity中将arraylist设置为public和static并传递它。

public static Arraylist<Division> arraylist;

在解析并将数据添加到arraylist后，调用fragment。在fragment中，您可以使用arraylist：

ArrayList<Division> list=MainActivity.arraylist;

- Mayank Raj

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有什么缺点？ - Mayank Raj

内存泄漏是使静态变量或对象失效的主要原因。 - Osama Aftab

如果Activity没有被销毁，那么内存泄漏会如何发生？你能解释一下吗？ - Bhaskar Jyoti Dutta