android - 如何在另一个活动中访问私有访问方法？

Question

我想在另一个活动中使用私有访问方法！。但我不知道该怎么做。或者我还能有什么其他方法。这是 AddSaleActivity 属性，getAllItems () 方法位于其末尾。

public class AddSaleActivity extends AppCompatActivity {

private Button buttonInsert;
private RadioGroup radio_sale_type;
private RadioButton radio_benzin;
private RadioButton radio_gasOil;
private String sale_name;
private SQLiteDatabase mDatabase;

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

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

    GasStationDBHelper dbHelper = new GasStationDBHelper(this);
    mDatabase = dbHelper.getWritableDatabase();

    buttonInsert = findViewById(R.id.button_insert);
    radio_sale_type = findViewById(R.id.radio_group_ful_type);
    radio_benzin = findViewById(R.id.radio_benzin);
    radio_gasOil = findViewById(R.id.radio_gasOil);


    buttonInsert.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            addItem();
        }
    });
}

private void addItem(){
    if (radio_sale_type.getCheckedRadioButtonId() == -1)
    {
        Toast.makeText(this, "لطفا نوع سوخت را انتخاب کنید!", Toast.LENGTH_SHORT).show();
        return;
    }
    if (radio_benzin.isChecked()){
        sale_name = "فروش بنزین";
    }
    if (radio_gasOil.isChecked()){
        sale_name = "فروش گازوئیل";
    }

    ContentValues cv = new ContentValues();
    cv.put(GasStationContract.GasStationEntry.COLUMN_NAME,sale_name);
    mDatabase.insert(GasStationContract.GasStationEntry.TABLE_NAME,null,cv);
    radio_sale_type.clearCheck();
    Toast.makeText(this, "فروش با موفقیت ثبت شد", Toast.LENGTH_SHORT).show();
    finish();
}

private Cursor getAllItems() {
    return mDatabase.query(
            GasStationContract.GasStationEntry.TABLE_NAME,
            null,
            null,
            null,
            null,
            null,
            GasStationContract.GasStationEntry.COLUMN_TIMESTAMP + " DESC"
    );
}}

要创建视图列表，我想在适配器的 HomeFragment 中使用 getAllItems()。但是这个方法有私有访问权限，不能做

public class HomeFragment extends Fragment {

private ArrayList<SaleItem> mSaleItems;
private HomeViewModel homeViewModel;
private RecyclerView mRecyclerView;
private GasStationAdapter mAdapter;
private RecyclerView.LayoutManager mlayoutManager;


public View onCreateView(@NonNull LayoutInflater inflater,
                         ViewGroup container, Bundle savedInstanceState) {
    homeViewModel =
            ViewModelProviders.of(this).get(HomeViewModel.class);
    View root = inflater.inflate(R.layout.fragment_home, container, false);
    //final TextView textView = root.findViewById(R.id.text_home);
    homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
        @Override
        public void onChanged(@Nullable String s) {
            //textView.setText(s);
        }
    });

    mRecyclerView = root.findViewById(R.id.recyclerView);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    mAdapter = new GasStationAdapter(getContext(), AddSaleActivity.getAllItems());
    mAdapter.swapCursor(AddSaleActivity.getAllItems());
    mRecyclerView.setAdapter(mAdapter);

    createSaleList();
    //buildRecyclerView();


    return root;
}


public void createSaleList(){
    mSaleItems = new ArrayList<>();
    mSaleItems.add(new SaleItem("فروش بنزین", "1254000 تومان", "12450 لیتر"));
    mSaleItems.add(new SaleItem("فروش گازویبل", "175000 تومان", "5000 لیتر"));
    mSaleItems.add(new SaleItem("فروش بنزین", "1254000 تومان", "12450 لیتر"));
}

public void buildRecyclerView(){
    mRecyclerView.setHasFixedSize(true);
    mlayoutManager = new LinearLayoutManager(getContext());
    //mAdapter = new SaleAdapter(mSaleItems);

    mRecyclerView.setLayoutManager(mlayoutManager);
    mRecyclerView.setAdapter(mAdapter);
}}

这是适配器

public class GasStationAdapter extends RecyclerView.Adapter<GasStationAdapter.GasStationViewHolder> {
private Context mContext;
private Cursor mCursor;

public GasStationAdapter(Context context, Cursor cursor) {
    mContext = context;
    mCursor = cursor;
}

public class GasStationViewHolder extends RecyclerView.ViewHolder {
    public TextView sale_nameText;

    public GasStationViewHolder(View itemView) {
        super(itemView);
        sale_nameText = itemView.findViewById(R.id.textView_sale_name);
    }
}


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

@Override
public void onBindViewHolder(GasStationViewHolder holder, int position) {
    if (!mCursor.moveToPosition(position)) {
        return;
    }
    String name = mCursor.getString(mCursor.getColumnIndex(GasStationContract.GasStationEntry.COLUMN_NAME));
    holder.sale_nameText.setText(name);
}

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

public void swapCursor(Cursor newCursor) {
    if (mCursor != null) {
        mCursor.close();
    }

    mCursor = newCursor;

    if (newCursor != null) {
        notifyDataSetChanged();
    }
}

}

标签： android

Answer 1

让你SQLiteOpenHelper成为单身人士：

class GasStationDBHelper extends SQLiteOpenHelper {
    private static volatile sInstance = null;

    static synchronized GasStationDBHelper instance(Context context) {
        if(sInstance == null)
            sInstance = new GasStationDBHelper(context.getApplicationContext());
        return sInstance;
    }

    Cursor getAllItems() {
        return getReadableDatabase().query(
            GasStationContract.GasStationEntry.TABLE_NAME,
            null,
            null,
            null,
            null,
            null,
            GasStationContract.GasStationEntry.COLUMN_TIMESTAMP + " DESC"
    );
    }
}

现在，无论您想要什么Cursor，只需使用GasStationDBHelper.instance(context).getAllItems()

编辑：另外，我不会亲自返回 a Cursor，但我会将查询结果映射到数据对象，以便您可以控制确保光标正确关闭，即：

List<Item> getAllItems() {
    try(Cursor c = getReadableDatabase().query(TABLE_NAME,null,null,null,null,null,COLUMN_TIMESTAMP + " DESC") {
        if(c == null || !c.moveToFirst)
            return new ArrayList<>();

        final List<Item> out = new ArrayList<>(c.getCount());
        while(c.moveToNext()) {
            out.add(Item.fromCursorRow(c)); 
        }
        return out;
    }
    return new ArrayList<>();
}

这将有助于确保您不会泄漏资源。