Question

所以我正确地为我的CursorAdapter实现了RecyclerView（afaik），但我得到了一些奇怪的错误。代码片段如下。非常感谢所有帮助，谢谢！

这是logcat：

以下是CursorRecyclerAdapter：

public abstract class CursorRecyclerAdapter<VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {

    protected boolean mDataValid;
    protected Cursor mCursor;
    protected int mRowIDColumn;

    public CursorRecyclerAdapter(Cursor c) {
        init(c);
    }

    void init(Cursor c) {
        boolean cursorPresent = c != null;
        mCursor = c;
        mDataValid = cursorPresent;
        mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;
        setHasStableIds(true);
    }

    @Override
    public final void onBindViewHolder (VH holder, int position) {
        if (!mDataValid) {
            throw new IllegalStateException("this should only be called when the cursor is valid");
        }
        if (!mCursor.moveToPosition(position)) {
            throw new IllegalStateException("couldn't move cursor to position " + position);
        }

        onBindViewHolder(holder, mCursor);
    }

    public abstract void onBindViewHolder(VH holder, Cursor cursor);

    public Cursor getCursor() {
        return mCursor;
    }

    @Override
    public int getItemCount () {
        if (mDataValid && mCursor != null) {
            return mCursor.getCount();
        } else {
            return 0;
        }
    }

    @Override
    public long getItemId (int position) {
        if(hasStableIds() && mDataValid && mCursor != null){
            if (mCursor.moveToPosition(position)) {
                return mCursor.getLong(mRowIDColumn);
            } else {
                return RecyclerView.NO_ID;
            }
        } else {
            return RecyclerView.NO_ID;
        }
    }

    /**
     * Change the underlying cursor to a new cursor. If there is an existing cursor it will be
     * closed.
     *
     * @param cursor The new cursor to be used
     */
    public void changeCursor(Cursor cursor) {
        Cursor old = swapCursor(cursor);
        if (old != null) {
            old.close();
        }
    }

    /**
     * Swap in a new Cursor, returning the old Cursor.  Unlike
     * {@link #changeCursor(Cursor)}, the returned old Cursor is <em>not</em>
     * closed.
     *
     * @param newCursor The new cursor to be used.
     * @return Returns the previously set Cursor, or null if there wasa not one.
     * If the given new Cursor is the same instance is the previously set
     * Cursor, null is also returned.
     */
    public Cursor swapCursor(Cursor newCursor) {
        if (newCursor == mCursor) {
            return null;
        }
        Cursor oldCursor = mCursor;
        mCursor = newCursor;
        if (newCursor != null) {
            mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
            mDataValid = true;
            // notify the observers about the new cursor
            notifyDataSetChanged();
        } else {
            mRowIDColumn = -1;
            mDataValid = false;
            // notify the observers about the lack of a data set
            notifyItemRangeRemoved(0, getItemCount());
        }
        return oldCursor;
    }

    /**
     * <p>Converts the cursor into a CharSequence. Subclasses should override this
     * method to convert their results. The default implementation returns an
     * empty String for null values or the default String representation of
     * the value.</p>
     *
     * @param cursor the cursor to convert to a CharSequence
     * @return a CharSequence representing the value
     */
    public CharSequence convertToString(Cursor cursor) {
        return cursor == null ? "" : cursor.toString();
    }
}

这是Recycler View适配器：

public class RVAdapter extends CursorRecyclerAdapter<RVAdapter.MyViewHolder> {

    private LayoutInflater inflater;
    CursorAdapter mCursorAdapter;
    Context mContext;
    public ManagerDatabaseAdapter managerDatabaseAdapter;

    public RVAdapter (Context context, Cursor cursor) {
        super(cursor);
        managerDatabaseAdapter = new ManagerDatabaseAdapter(context);
        Message.message(context, cursor.toString());
        mContext = context;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        Message.message(mContext, "Holder Called");
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.custom_row, parent, false);
        MyViewHolder holder = new MyViewHolder(view);
        return holder;
    }


    @Override
    public void onBindViewHolder(MyViewHolder holder, Cursor cursor) {
        cursor.moveToFirst();
        Message.message(mContext, "Binder Called");
        int banana = cursor.getColumnIndex("Codes");
        Message.message(mContext, banana);
        super.onBindViewHolder(holder, banana);
    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {

        TextView Title;

         MyViewHolder(View itemView) {
            super(itemView);
            Title = (TextView) itemView.findViewById(R.id.Row_Header);
            //Body = (TextView) itemView.findViewById(R.id.Row_Footer);
        }
    }
}

最后，这是MainActivity.java：

public class MainActivity extends AppCompatActivity {

    public static final String EXTRA_MESSAGE = "com.nick.mowen.receiptmanager.LOCATION";
    public RecyclerView RV;
    private RVAdapter adapter;
    ManagerDatabaseAdapter managerDatabaseAdapter;
    RecyclerView.LayoutManager layoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        managerDatabaseAdapter = new ManagerDatabaseAdapter(this);
        setContentView(R.layout.activity_main);
        adapter = new RVAdapter(this, managerDatabaseAdapter.getTheCursor());
        RV = (RecyclerView) findViewById(R.id.mainV);
        layoutManager = new LinearLayoutManager(this);
        RV.setLayoutManager(layoutManager);
        RV.setAdapter(adapter);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        //  getMenuInflater().inflate(R.menu.menu_main, li)
        return true;
    }

    public static void getData() {

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            Intent intent = new Intent(this, SettingsActivity.class);
            intent.putExtra(EXTRA_MESSAGE, true);
            startActivity(intent, ActivityOptions.makeSceneTransitionAnimation(this).toBundle());
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /*@Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        TextView userText= (TextView) view;
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }*/

    public void addInstance(View view) {
        Intent intent = new Intent(this, LocationAdder.class);
        intent.putExtra(EXTRA_MESSAGE, true);
        startActivity(intent, ActivityOptions.makeSceneTransitionAnimation(this).toBundle());
    }
}

Android - 游标适配器和回收站视图的问题

0 个答案: