java - 从ListView到RecyclerView

Question

我正在开发一个简单的应用程序，用于跟踪我正在观看的节目，起初我使用的是 ListView，但现在我想使用 RecyclerView。我将所有节目存储在本地数据库中。但是，我无法正确地将代码转换为 RecyclerView。我还无法测试它，因为我正在努力解决以下行的错误:

   showAdapter = new ArrayAdapter<Show>(this, showArrayAdapter); // the error

Error:(62, 56) error: incompatible types: List cannot be converted to int

public class MainActivity extends AppCompatActivity {
private Button btn;
private RecyclerView recyclerView;
private List<Show> showArrayAdapter;
private ShowsAdapter showAdapter;
private DataSource datasource;
List<Show> shows = datasource.getAllShows();

public static final String INTENT_DETAIL_ROW_NUMBER = "Row number";
public static final String INTENT_DETAIL_REMINDER_TEXT = "Reminder text";
public static final int REQUESTCODE = 2;
public static final String EXTRA_SHOW_ID = "extraShowId";

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    datasource = new DataSource(this);
    shows = datasource.getAllShows();
    recyclerView = (RecyclerView) findViewById(R.id.main_list);
    showArrayAdapter = new ArrayList<Show>();


    recyclerView.setAdapter(showAdapter);

    registerForContextMenu(recyclerView);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.taskView);
        fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivityForResult(new Intent(MainActivity.this, CreateShowActivity.class), 1);
            }
        });
    }

    private void updateUI() {
        if (showAdapter == null) {
            showAdapter = new ArrayAdapter<Show>(this, showArrayAdapter); // the error
            recyclerView.setAdapter(showAdapter);
        } else {
            showAdapter.notifyDataSetChanged();
        }
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 1) {
            if (resultCode == RESULT_OK) {
                //Handle data
                long showId = data.getLongExtra(EXTRA_SHOW_ID, -1);
                if (showId != -1) {
                    Show show = datasource.getShow(showId);
                    showArrayAdapter.add(show);
                    updateUI();

                }
            }
        }
        if (requestCode == 2) {
            if (resultCode == RESULT_OK) {
                updateUI();
            }
        }
    }
}

我的适配器

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

    private ArrayAdapter<Show> mShows;
    private Context mContext;

    public ShowsAdapter(Context mContext, ArrayAdapter<Show> mShows) {
        this.mContext = mContext;
        this.mShows = mShows;
    }

    @Override
    public ShowsAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = LayoutInflater.from(mContext).inflate(android.R.layout.activity_list_item, null);

        // Return a new holder instance
        ShowsAdapter.ViewHolder viewHolder = new ShowsAdapter.ViewHolder(view);
        return viewHolder;


    }

    @Override
    public void onBindViewHolder(ShowsAdapter.ViewHolder holder, final int position) {

        final Show show =  mShows.getItem(position);

        holder.textView.setText(show.getShow());

        holder.mView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(mContext, EditShowActivity.class);
                intent.putExtra(INTENT_DETAIL_ROW_NUMBER, position);
                intent.putExtra(INTENT_DETAIL_REMINDER_TEXT, show.getShow());
                ((MainActivity) mContext).startActivityForResult(intent, REQUESTCODE);
            }
        });

        holder.mView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                mShows.remove(mShows.getItem(position));
                notifyItemRemoved(position);
                notifyItemRangeChanged(position,mShows.getCount());
                return true;
            }
        });

    }

    @Override
    public int getItemCount() {
        return mShows.getCount();
    }



    public static class ViewHolder extends RecyclerView.ViewHolder{

        public View mView;
        public TextView textView;

        //Constructor
        public ViewHolder(View v) {


            super(v);
            textView = (TextView) v.findViewById(android.R.id.text1);
            mView = v;
        }
    }
}

由于我目前正在努力解决这个问题并尝试了许多不同的事情，因此我的代码可能无法工作。如果您看到其他任何内容请告诉我

更新:
根据大家收到的意见，我做了很多改变:

 private DataSource datasource;
 private Button btn;
 private RecyclerView recyclerView;
 private List<Show> shows;

 private ShowsAdapter showAdapter;

在初始化之前添加布局管理器并删除数据源

DataSource datasource = new DataSource(this);
    List<Show> shows = datasource.getAllShows();
    recyclerView = (RecyclerView) findViewById(R.id.main_list);

    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setAdapter(showAdapter);

更新了我的 UpdateUI()

private void updateUI() {
        if (showAdapter == null) {
            showAdapter = new ShowsAdapter(this, shows); // the error
            recyclerView.setAdapter(showAdapter);
        } else {
            showAdapter.notifyDataSetChanged();
        }
    }

并匹配showAdapters.java中的类型

public ShowsAdapter(Context mContext, List<Show> mShows) {
        this.mContext = mContext;
        this.mShows = mShows;
    }

但是在启动时我收到以下错误

E/RecyclerView: No adapter attached; skipping layout E/RecyclerView: No adapter attached; skipping layout

和

java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {com.example.kevin.androidapp/com.example.kevin.androidapp.MainActivity}: java.lang.NullPointerException

Caused by: java.lang.NullPointerException at com.example.kevin.androidapp.MainActivity.onActivityResult(MainActivity.java:77)

位于 onActivityResult Show show = datasource.getShow(showId);

我的createShowActivity

public class CreateShowActivity extends AppCompatActivity {
    private Button btn;
    private EditText showDescription;
    private DataSource datasource;

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

        showDescription = (EditText)this.findViewById(R.id.showDescription);
        datasource = new DataSource(this);

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

                long assignmentId = datasource.createShows(showDescription.getText().toString());
                Intent resultIntent = new Intent();
                resultIntent.putExtra(MainActivity.EXTRA_SHOW_ID, assignmentId);
                setResult(Activity.RESULT_OK, resultIntent);
                finish();

            }
        });
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }
}

Answer 1

列表无法转换为int？

这不是您标记的行，除非 getAllShows()返回一个整数...

<小时/>

不过，您正在混合适配器。 Recyclerview不使用ArrayAdapter。

你完成了这门课

 ShowsAdapter extends RecyclerView.Adapter

但是你不使用它

   showAdapter = new ArrayAdapter<Show>(this, showArrayAdapter); // the error
    recyclerView.setAdapter(showAdapter);

<小时/>

还有showArrayAdapter = new ArrayList<Show>();根本不是适配器。您已经拥有 List<Show> shows

和

datasource = new DataSource(this);
shows = datasource.getAllShows();

首先，如果您不想出现空指针异常，则需要停止获取字段中的显示。

private List<Show> shows; // = datasource.getAllShows();

<小时/>

综上所述，要使用Recyclerview

1) 添加布局管理器
2)使用正确的Adapter类
3)使用正确的列表

RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(mLayoutManager);

showAdapter = new ShowsAdapter(this, shows);

recyclerView.setAdapter(showAdapter);

<小时/>

附加说明。

这种对 Activity 的强制转换是不必要的，并且当您想在其他 Activity 中使用此适配器时会导致问题。

((MainActivity) mContext).startActivityForResult