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社区首页 >问答首页 >想要实现notifyDataSetChanged或自动刷新到我的RecyclerView，但它不能工作

问想要实现notifyDataSetChanged或自动刷新到我的RecyclerView，但它不能工作
EN

Stack Overflow用户
提问于 2016-04-01 20:05:10
回答 2查看 846关注 0票数 4

我想实现notifyDataSetChanged或对我的RecyclerView进行自动刷新，但是它不起作用，我尝试了很多方法来解决这个问题，但不幸的是，所有方法最终都会崩溃，有些方法无法工作。我是新手，所以，请帮我解决这个问题。同时也想知道，这是创建DataAapter引用的正确方法吗？

DataAdapter数据文件；(下面给出的完整代码)

如果不是，那是怎么回事？

使用此代码(如下所示)，我的应用程序在打开时崩溃，希望知道我做错了什么，这样我就可以从错误中吸取教训。))谢谢

代码语言：javascript
运行
复制
public class DataAdapter extends RecyclerView.Adapter<DataAdapter.ViewHolder> {
public static String Camp_ID[] = new String[15];
private ArrayList<AndroidVariables> android;
private Context context;
AnimatorSet set;
DataAdapter dataAdapter

String url = "_URL";



public DataAdapter(ArrayList<AndroidVariables> android) {
    this.context = context;
    this.android = android;
    if (OffersFragment.srl.isRefreshing()) {
        OffersFragment.srl.setRefreshing(false);
    }
}


@Override
public DataAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
    if (android.get(i).getCamp_ID().equals("1")) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_list_offer_big, viewGroup, false);

        return new ViewHolder(view);
    }
    View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_list, viewGroup, false);
    return new ViewHolder(view);
}

@Override
public int getItemViewType(int i) {
    return i;
}


public void myNotifyDataSetChanged()
{
    this.notifyDataSetChanged();

}

@Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {

    Context context = viewHolder.p_img.getContext();
    viewHolder.p_name.setText(android.get(i).getName());
    viewHolder.p_quant.setText(android.get(i).getVer());
    viewHolder.p_cat.setText(android.get(i).getApi());
    viewHolder.p_earn.setText("₹" + android.get(i).getCash());
    Camp_ID[i] = android.get(i).getCamp_ID();
    Picasso.with(context).load(url + android.get(i).getImage()).into(viewHolder.p_img);


    dataAdapter.myNotifyDataSetChanged();
}

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

}

public class ViewHolder extends RecyclerView.ViewHolder {
    private TextView p_name, p_quant, p_cat, p_earn;
    private ImageView p_img, plus;

    public ViewHolder(View view) {
        super(view);

        p_name = (TextView) view.findViewById(R.id.list_product);
        p_quant = (TextView) view.findViewById(R.id.list_quantity);
        p_cat = (TextView) view.findViewById(R.id.list_category);
        p_earn = (TextView) view.findViewById(R.id.earning);
        p_img = (ImageView) view.findViewById(R.id.list_productimg);
        plus = (ImageView) view.findViewById(R.id.plusoffers);

        plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                plus.setImageResource(R.drawable.check_small);
            //DO_ANY_THING
            }
        });
    }
}
}

日志

代码语言：javascript
运行
复制
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime: FATAL EXCEPTION: main
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime: Process:   earn.free.cashback, PID: 24357
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:   java.lang.NullPointerException: Attempt to invoke virtual method 'void     earn.free.cashback.DataAdapter.myNotifyDataSetChanged()' on a null   object reference
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at earn.free.cashback.DataAdapter.onBindViewHolder(DataAdapter.java:94)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  earn.free.cashback.DataAdapter.onBindViewHolder(DataAdapter.java:30)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.jav     a:5453)
 04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:     5486)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at   android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.    java:4723)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at   android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.    java:4599)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManag    er.java:1988)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.ja    va:1384)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1347    )
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManag    er.java:574)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:300    3)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2881)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3265)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:59    6)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at     android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
 04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.ja    va:1087)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.    java:797)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:    811)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at   android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1695)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScro    llingViewBehavior.java:122)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at  android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavio    r.java:42)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at    android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(A    ppBarLayout.java:1149)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at   android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:    810)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at     android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at   android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1187)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.View.layout(View.java:15671)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.view.ViewGroup.layout(ViewGroup.java:5038)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:     at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
04-02 02:17:11.820 24357-24357/? E/AndroidRuntime:  at android.view.View.l
adapter
android-recyclerview
android-adapter
notifydatasetchanged
android
EN

回答 2

Stack Overflow用户

发布于 2016-04-01 21:54:43

Shadab的信息是正确的，尽管关于初始化，我建议从您的dataAdapter类中删除DataAdapter变量，并将它添加到您想要访问它的活动中；在onCreate()中初始化它。

代码语言：javascript
运行
复制
public void onCreate(Bundle savedInstanceState) {
    //Initialize data set
    myAndroidData = new ArrayList<>();
    //Initialize data adapter and assign it to a recycler view
    myDataAdapter = new DataAdapter(myAndroidData);
    myRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    myRecyclerView.setAdapter(myDataAdapter);
    super.onCreate(savedInstanceState);
}

从myAndroidData中添加或删除项后，调用myDataAdapter.notifyDataSetChanged();刷新显示。因为notifyDataSetChanged()是父RecyclerView类中的一个公共函数，所以您的myNotifyDataSetChanged()函数是不必要的，可以删除。在创建适配器后避免调用myAndroidData = new ArrayList<AndroidVariables>()，因为dataAdapter.android仍然会引用您使用它初始化的列表，并且notifyDataSetChanged()将不再像您希望的那样工作。

还建议您不要从notifyDataSetChanged()调用onBindViewHolder()。onBindViewHolder只应用于设置视图持有人中显示的内容，而不是RecyclerView本身。

将onBindViewHolder()函数更新为

代码语言：javascript
运行
复制
@Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {

    Context context = viewHolder.p_img.getContext();
    viewHolder.p_name.setText(android.get(i).getName());
    viewHolder.p_quant.setText(android.get(i).getVer());
    viewHolder.p_cat.setText(android.get(i).getApi());
    viewHolder.p_earn.setText("₹" + android.get(i).getCash());
    Camp_ID[i] = android.get(i).getCamp_ID();
    Picasso.with(context).load(url + android.get(i).getImage()).into(viewHolder.p_img);

}
票数 1
EN

Stack Overflow用户

发布于 2016-04-01 21:42:46

您正在尝试在myNotifyDataSetChanged()实例上调用null adapter。您可以直接调用notifyDataSetChanged()而不是调用dataAdapter.myNotifyDataSetChanged();

票数 0
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/36364948

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