Question

我正在从android中的数据库创建一个arraylist，用于回收器视图的适配器：

RecyclerView recyclerView = (RecyclerView) getView().findViewById(R.id.homeRecycler);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
ArrayList<StocksforHome> stockList = new ArrayList<>();
DbInteract interact = new DbInteract(getContext());
Cursor cursor = interact.readtable();
HomeFragmentAdapter homeFragmentAdapter = new HomeFragmentAdapter(stockList, getContext());
GetHomeData getHomeData = new GetHomeData(getContext(),homeFragmentAdapter);
int i=0;
stockList.clear();
while(cursor.moveToNext())
{
    StocksforHome temp = new StocksforHome();
    temp.stock = cursor.getString(cursor.getColumnIndex(eventDBcontract.ListofItem.columnsym));
    stockList.add(temp);
}
homeFragmentAdapter.addall(stockList);
Log.d(tag,String.valueOf(stockList.size()) + " " + String.valueOf(cursor.getCount()));
recyclerView.setAdapter(homeFragmentAdapter);

数据库中只有一个数据，但arraylist的大小仍然是2.我检查了额外数据是否与第一个数据重复。日志报告：

D/HomeFragment: 2 1

我制作了一个自定义适配器。它的addall方法是：

 public void addall(ArrayList<StocksforHome> more)
{
    stockArrayList.addAll(more);
    notifyDataSetChanged();
}

知道为什么会这样，以及如何解决它？

Answer 1

这是因为适配器中的stockList和代码段中的stockList是相同的引用，因此结果项会被添加两次。要修复此适配器，需要使用自己的List实例。

首先添加：

stockList.add(temp);

第二次添加：

homeFragmentAdapter.addall(stockList);

像这样修复适配器：

HomeFragmentAdapter {

    private final List<StocksforHome> stockList = new Arraylist<>();

    public HomeFragmentAdapter(Context context) {
    }

    public void addall(List<StocksforHome> more) {
        stockList.clear();
        stockList.addAll(more);
        notifyDataSetChanged();
    }
}

Answer 2

试试这个。

    RecyclerView recyclerView = (RecyclerView) getView().findViewById(R.id.homeRecycler);
    recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    ArrayList<StocksforHome> stockList = new ArrayList<>();
    DbInteract interact = new DbInteract(getContext());
    Cursor cursor = interact.readtable();
    HomeFragmentAdapter homeFragmentAdapter;
    GetHomeData getHomeData = new GetHomeData(getContext(), homeFragmentAdapter);
    int i = 0;
    // clear and add data in your code 
    stockList.clear();
    while (cursor.moveToNext()) {
        StocksforHome temp = new StocksforHome();
        temp.stock = cursor.getString(cursor.getColumnIndex(eventDBcontract.ListofItem.columnsym));
        stockList.add(temp);
    }
    if (homeFragmentAdapter == null) {
        homeFragmentAdapter = new HomeFragmentAdapter(stockList, getContext());

        Log.d(tag, String.valueOf(stockList.size()) + " " + String.valueOf(cursor.getCount()));
        recyclerView.setAdapter(homeFragmentAdapter);
    } else {
        // add all data 
        homeFragmentAdapter.addall(stockList);
    }

首先，获取数据

其次，将其设置为适配器

homeFragmentAdapter = new HomeFragmentAdapter(stockList, getContext());

刷新代码中的数据

homeFragmentAdapter.addall(stockList);

数据在arraylist中自动存储多次

2 个答案: