Question

我是Android和Java的新手，但在我的第一个应用程序中，我有点在做Play Store，这是您在Play Store上看到的第一件事，然后转到第二个活动，并在那里查看整个列表。我已经建立了水平ArrayList，并且也成功建立了第二个活动的Cardview，我的ArrayList是静态的，这意味着它没有使用任何服务器。

我的问题是如何通过位于其中的适配器将MainActivity的数据发送到MainActivity2。

这是我的主要活动，我的数据位于其中：

public class MainActivity extends AppCompatActivity {

private ArrayList<SectionDataModel> allSampleData;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    allSampleData = new ArrayList<>();


    RecyclerView recyclerView = findViewById(R.id.my_recycler_view1);
    recyclerView.setHasFixedSize(true);
    RecyclerViewDataAdapter adapter = new RecyclerViewDataAdapter(allSampleData, this);
    recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
    recyclerView.setAdapter(adapter);


    EssentialData();



}

public void EssentialData() {
    SectionDataModel Unit1 = new SectionDataModel();
    Unit1.setHeaderTitle("Unit 1");


    ArrayList<SingleItemModel> singleItemModels = new ArrayList<>();

    singleItemModels.add(new SingleItemModel("Word ", "Pronunciation", "Example", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.soft));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));
    singleItemModels.add(new SingleItemModel("The Apple", "Apple Store Is Open", "Description book", R.drawable.alferet));


    Unit1.setAllItemInSection(singleItemModels);
    allSampleData.add(Unit1);


}
  }

我的SectionDataAdapter只能从其中发送数据到Second MainActivity，因为如果我从MainActivity本身进行操作，它会返回Null：

public class SectionDataAdapter extends RecyclerView.Adapter<SectionDataAdapter.SingleItemRowHolder>{

private final Context mContext;

private ArrayList<SingleItemModel> itemModels;


//the constructor
public SectionDataAdapter(ArrayList<SingleItemModel> itemModels, Context mContext) {
    this.itemModels = itemModels;
    this.mContext = mContext;
}


@NonNull
@Override
public SingleItemRowHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_single_card, null);
    SingleItemRowHolder singleItemRowHolder = new SingleItemRowHolder(view);
    return singleItemRowHolder;
}




@Override
public void onBindViewHolder(@NonNull SingleItemRowHolder holder, int position) {
    SingleItemModel itemModel = itemModels.get(position);
    holder.tvTitle.setText(itemModel.getWord());
    holder.mitemImage.setImageResource(itemModel.getImage());
}


@Override
public int getItemCount() {return (null != itemModels ? itemModels.size() : 0);}

public class SingleItemRowHolder extends RecyclerView.ViewHolder {
    protected TextView tvTitle;
    protected ImageView mitemImage;



    public SingleItemRowHolder(final View itemView) {

        super(itemView);
        //Intent to start next activity
        final Intent intent = new Intent(mContext, ActivityDialogTheme.class);
        final Intent intent1 = new Intent(mContext, MainActivity2.class);

        final Activity activity = (Activity) mContext;

        this.mitemImage = itemView.findViewById(R.id.itemImage);
        this.tvTitle = itemView.findViewById(R.id.tvTitle);


        itemView.setOnClickListener(new View.OnClickListener(){


            @Override
            public void onClick(View v){
                Toast.makeText(v.getContext(), tvTitle.getText(), LENGTH_SHORT).show();
                //passing data to Tab1Fragment

                mContext.startActivity(intent1);
            }
        });
        itemView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                Toast.makeText(mContext,tvTitle.getText(), Toast.LENGTH_SHORT).show();
                mContext.startActivity(intent);

                //appearing animation
                activity.overridePendingTransition(R.anim.bottom_in, R.anim.fade_in_right);
                return true;
            }
        });
        }
    }
}

MainActivity2正在托管3个选项卡，在其中一个中我也需要接收它，因为我声明了所有选项卡Fragment，并且每个选项卡的Fragment的功能都类似于MainActivity的适配器（SectionDataAdapter），它将显示ArrayLists的项目。这意味着我还必须在所有片段中都接收MainActivity的ArrayList。

这是我的Tab1Fragment：

public class Tab1Fragment extends Fragment {
public Tab1Fragment() {
    // Required empty public constructor
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.tab1_fragment, container, false);
    return view;
}
  }

当然还有我的RecyclerViewAdapter，它显示了ArrayLaists的物品

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder0> {
private Context mContext ;
private ArrayList<SingleItemModel> mData ;


//the constructor
public RecyclerViewAdapter(Context mContext, ArrayList<SingleItemModel> mData) {
    this.mContext = mContext;
    this.mData = mData;
}



@NonNull
@Override
public MyViewHolder0 onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view;
    LayoutInflater mInflater = LayoutInflater.from(mContext);
    view = mInflater.inflate(R.layout.cardview_item_book, parent, false);
    return new MyViewHolder0(view);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder0 holder, final int position) {
    holder.tv_book_title.setText(mData.get(position).getWord());
    holder.img_book_thumbnail.setImageResource(mData.get(position).getImage());

        holder.cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(mContext,Book_Activity.class);
                // passing data to the book activity

                //intent.putExtra("key_Word",value);
                intent.putExtra("Word",mData.get(position).getWord());
                intent.putExtra("Pronunciation",mData.get(position).getPronunciation());
                intent.putExtra("Examples&Explanation",mData.get(position).getExamples());
                //intent.putExtra("Definition",mData.get(position).getDefinition());
                intent.putExtra("WordImage",mData.get(position).getImage());
                // start the activity
                mContext.startActivity(intent);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mData.size();
    }

    public static class MyViewHolder0 extends RecyclerView.ViewHolder {
        TextView tv_book_title;
        ImageView img_book_thumbnail;
        CardView cardView ;

        public MyViewHolder0(View itemView) {
            super(itemView);
            tv_book_title =  itemView.findViewById(R.id.book_title_id) ;
            img_book_thumbnail = itemView.findViewById(R.id.book_img_id);
            cardView =  itemView.findViewById(R.id.cardview_id);
        }
    }



}

有人帮助我..！

Answer 1

您需要使用 Intent 才能将数据发送到另一个活动

@Override
  public void onClick(View v) {

    Book book = new Book(mBkTitle.getText().toString(),
            mBkAuthor.getText().toString());

    Intent intent = new Intent(MainActivity.this, BookActivity.class);
    intent.putExtra("Book", book);
    startActivity(intent);
  }

数据需要从Parcelable扩展

public class Book implements Parcelable {
  // book basics
  private String title;
  private String author;
}

使用http://www.jsonschema2pojo.org/帮助您使类可包裹。

查看本教程

https://code.tutsplus.com/tutorials/how-to-pass-data-between-activities-with-android-parcelable--cms-29559

将MainActivity的数据传递给Tab Fragment

1 个答案: