如何读取片段使用的对象

Question

首先，我希望我的问题是清楚的。如果不是请评论我会努力让它变得更好！

我有一个关于将项目放入数组列表的问题。我正在使用 master/detail 流程（android 工作室中的标准项目选项）作为我的应用程序的基础。我已经对其进行了修改，但下面是原始模板中的代码以简化我的问题。对于我的问题，我认为涉及三个活动。主要 activity、详细信息 activity、mysavedbooks 和片段 activity。

我的问题在详细信息 activity 中有一个 fab 按钮。我想要做的是将当前显示的项目保存在 activity mysavedbooks 中名为 Saveditems 的新数组列表中。

我如何读取项目（当前由扩展片段的详细信息activity 显示）并将其放入 saveditems 数组列表中。

您好，马泰斯

下面是主要内容activity

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


import matthijs.bookshelf.dummy.DummyContent;

import java.util.List;

/**
 * An activity representing a list of books. This activity
 * has different presentations for handset and tablet-size devices. On
 * handsets, the activity presents a list of items, which when touched,
 * lead to a {@link bookDetailActivity} representing
 * item details. On tablets, the activity presents the list of items and
 * item details side-by-side using two vertical panes.
 */
public class bookListActivity extends AppCompatActivity {

/**
 * Whether or not the activity is in two-pane mode, i.e. running on a tablet
 * device.
 */
private boolean mTwoPane;

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    toolbar.setTitle(getTitle());

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    View recyclerView = findViewById(R.id.book_list);
    assert recyclerView != null;
    setupRecyclerView((RecyclerView) recyclerView);

    if (findViewById(R.id.book_detail_container) != null) {
        // The detail container view will be present only in the
        // large-screen layouts (res/values-w900dp).
        // If this view is present, then the
        // activity should be in two-pane mode.
        mTwoPane = true;
    }
}

private void setupRecyclerView(@NonNull RecyclerView recyclerView) {
    recyclerView.setAdapter(new SimpleItemRecyclerViewAdapter(DummyContent.ITEMS));
}

public class SimpleItemRecyclerViewAdapter
        extends RecyclerView.Adapter<SimpleItemRecyclerViewAdapter.ViewHolder> {

    private final List<DummyContent.DummyItem> mValues;

    public SimpleItemRecyclerViewAdapter(List<DummyContent.DummyItem> items) {
        mValues = items;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.book_list_content, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        holder.mItem = mValues.get(position);
        holder.mIdView.setText(mValues.get(position).id);
        holder.mContentView.setText(mValues.get(position).content);

        holder.mView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mTwoPane) {
                    Bundle arguments = new Bundle();
                    arguments.putString(bookDetailFragment.ARG_ITEM_ID, holder.mItem.id);
                    bookDetailFragment fragment = new bookDetailFragment();
                    fragment.setArguments(arguments);
                    getSupportFragmentManager().beginTransaction()
                            .replace(R.id.book_detail_container, fragment)
                            .commit();
                } else {
                    Context context = v.getContext();
                    Intent intent = new Intent(context, bookDetailActivity.class);
                    intent.putExtra(bookDetailFragment.ARG_ITEM_ID, holder.mItem.id);

                    context.startActivity(intent);
                }
            }
        });
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        public final View mView;
        public final TextView mIdView;
        public final TextView mContentView;
        public DummyContent.DummyItem mItem;

        public ViewHolder(View view) {
            super(view);
            mView = view;
            mIdView = (TextView) view.findViewById(R.id.id);
            mContentView = (TextView) view.findViewById(R.id.content);
        }

        @Override
        public String toString() {
            return super.toString() + " '" + mContentView.getText() + "'";
        }
    }
}

}

下面是详细信息 activity。

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.NavUtils;
import android.view.MenuItem;

/**
 * An activity representing a single book detail screen. This
 * activity is only used narrow width devices. On tablet-size devices,
 * item details are presented side-by-side with a list of items
 * in a {@link bookListActivity}.
 */
public class bookDetailActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_book_detail);
    Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "saved book", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();



        }
    });

    // Show the Up button in the action bar.
    ActionBar actionBar = getSupportActionBar();
    if (actionBar != null) {
        actionBar.setDisplayHomeAsUpEnabled(true);
    }

    // savedInstanceState is non-null when there is fragment state
    // saved from previous configurations of this activity
    // (e.g. when rotating the screen from portrait to landscape).
    // In this case, the fragment will automatically be re-added
    // to its container so we don't need to manually add it.
    // For more information, see the Fragments API guide at:
    //
    // http://developer.android.com/guide/components/fragments.html
    //
    if (savedInstanceState == null) {
        // Create the detail fragment and add it to the activity
        // using a fragment transaction.
        Bundle arguments = new Bundle();
        arguments.putString(bookDetailFragment.ARG_ITEM_ID,
                getIntent().getStringExtra(bookDetailFragment.ARG_ITEM_ID));
        bookDetailFragment fragment = new bookDetailFragment();
        fragment.setArguments(arguments);
        getSupportFragmentManager().beginTransaction()
                .add(R.id.book_detail_container, fragment)
                .commit();
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == android.R.id.home) {
        // This ID represents the Home or Up button. In the case of this
        // activity, the Up button is shown. Use NavUtils to allow users
        // to navigate up one level in the application structure. For
        // more details, see the Navigation pattern on Android Design:
        //
        // http://developer.android.com/design/patterns/navigation.html#up-vs-back
        //
        NavUtils.navigateUpTo(this, new Intent(this, bookListActivity.class));
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

下面是片段

package matthijs.bookshelf;

import android.app.Activity;
import android.support.design.widget.CollapsingToolbarLayout;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import matthijs.bookshelf.dummy.DummyContent;

/**
 * A fragment representing a single book detail screen.
 * This fragment is either contained in a {@link bookListActivity}
 * in two-pane mode (on tablets) or a {@link bookDetailActivity}
 * on handsets.
 */
public class bookDetailFragment extends Fragment {
    /**
     * The fragment argument representing the item ID that this fragment
     * represents.
     */
    public static final String ARG_ITEM_ID = "item_id";

    /**
     * The dummy content this fragment is presenting.
     */
    private DummyContent.DummyItem mItem;

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the
     * fragment (e.g. upon screen orientation changes).
     */
    public bookDetailFragment() {
    }

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

    if (getArguments().containsKey(ARG_ITEM_ID)) {
        // Load the dummy content specified by the fragment
        // arguments. In a real-world scenario, use a Loader
        // to load content from a content provider.
        mItem = DummyContent.ITEM_MAP.get(getArguments().getString(ARG_ITEM_ID));

        Activity activity = this.getActivity();
        CollapsingToolbarLayout appBarLayout = (CollapsingToolbarLayout) activity.findViewById(R.id.toolbar_layout);
        if (appBarLayout != null) {
            appBarLayout.setTitle(mItem.content);
        }
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.book_detail, container, false);

    // Show the dummy content as text in a TextView.
    if (mItem != null) {
        ((TextView) rootView.findViewById(R.id.book_detail)).setText(mItem.details);
    }

    return rootView;
}
}

Mysavedbooks activity

package matthijs.tuinierv2;

        import java.util.ArrayList;
        import java.util.List;

/**
 * Created by Matthijs on 12-2-2016.
 */
public class Mysavedbooks {

    public static final List<DummyContent.DummyItem> SavedItems= new   ArrayList<DummyContent.DummyItem>();

}

Answer 1

我暂时解决了问题，除了双窗格模式。我需要进一步查看双窗格模式的解决方案。我认为可以用更好的方式完成，但这是解决方案。

如果您有更好的解决方案欢迎评论。

我在 ItemDetailActivity 中添加了字符串

public static  String SAVED_ITEM_ID;

我在bookListActivity这部分添加了一行代码：

` @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        holder.mItem = mValues.get(position);
        holder.mIdView.setText(mValues.get(position).id);
        holder.mContentView.setText(mValues.get(position).content);

    holder.mView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mTwoPane) {
                Bundle arguments = new Bundle();
                arguments.putString(bookDetailFragment.ARG_ITEM_ID, holder.mItem.id);
                bookDetailFragment fragment = new bookDetailFragment();
                fragment.setArguments(arguments);
                getSupportFragmentManager().beginTransaction()
                        .replace(R.id.book_detail_container, fragment)
                        .commit();
            } else {
                Context context = v.getContext();
                Intent intent = new Intent(context, bookDetailActivity.class);
                intent.putExtra(bookDetailFragment.ARG_ITEM_ID,  holder.mItem.id);

                //THE line of code I ADDED
                itemDetailActivity.SAVED_ITEM_ID = holder.mItem.id;

                context.startActivity(intent);
            }
        }
    });
}`

这是我在 bookDetailActivity 中添加的代码，用于检索显示在 itemdetailactivity 中的当前书籍，从而成为片段。

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_item_detail);
    Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton)findViewById(R.id.fabdetail);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            //code i added to retrieve the current item and save it in 
            int SAVED_ITEM_ID_INT = Integer.parseInt(SAVED_ITEM_ID);
            ItemListActivity.PlantItem SAVED_ITEM = ItemListActivity.ITEMS.get(SAVED_ITEM_ID_INT);
            Mysavedbooks.SavedItems.add(SAVED_ITEM);


           Snackbar.make(view,"Book saved to My books", Snackbar.LENGTH_LONG).setAction("Action", null).show();



        }
    });

如何读取片段使用的对象

How to read object which is used by a fragment

android

arraylist

fragment

master-detail