适配器中的Android上下文操作栏？

我正在尝试在我的应用程序中实现上下文actionbar。然而，当我尝试在适配器中使用Startactionmode方法时，我找不到这样做的方法

我试过：

mActionMode = ((MainActivity)c).startActionMode(new MyActionModeCallback());

这给了我一个错误

java.lang.NullPointerException:尝试调用虚拟方法的 在CustomerListAdapter$ViewHolder$1.onClick（CustomerListAdapter.java:62）

爪哇语：62是

mActionMode = ((MainActivity)c).startActionMode(new MyActionModeCallback());

顺便说一句，我正在导入android.view.ActionMode；它是mainactivity实现actionbaractivity中的一个选项卡片段

我的适配器类

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

public ViewHolder(final View itemView,int ViewType, final Context c) {   

下面是我的适配器代码

    package com.thecueapps.cue_business;

    import android.content.Context;
    import android.support.v7.widget.CardView;
    import android.support.v7.widget.RecyclerView;
    import android.view.ActionMode;
    import android.view.LayoutInflater;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;
    import android.widget.TextView;

    import com.parse.ParseUser;

    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    import java.util.List;


    public class CustomerListAdapter extends RecyclerView.Adapter<CustomerListAdapter.ViewHolder>{
    protected List<ParseUser> mCustomers;

    Context context;
    public static class ViewHolder extends RecyclerView.ViewHolder {

        TextView Name_fiedl;
        TextView Number_ppl_field;
        TextView Time_field;
        Context contxt;
        Context contxt1;
        private CardView cardView;
        private ImageView circleview;
        public ActionMode mActionMode;




        public ViewHolder(final View itemView,int ViewType, final Context c) {                 // Creating ViewHolder Constructor with View and viewType As a parameter
            super(itemView);
            contxt = c;

            //itemView.setClickable(true);
            //itemView.setOnClickListener(this);
            // Here we set the appropriate view in accordance with the the view type as passed when the holder object is created
            Name_fiedl = (TextView) itemView.findViewById(R.id.text_name); // Creating TextView object with the id of textView from item_row.xml
            Number_ppl_field = (TextView) itemView.findViewById(R.id.number_ppl);// Creating ImageView object with the id of ImageView from item_row.xml
            circleview=(ImageView) itemView.findViewById(R.id.circle_ppl);
            Time_field=(TextView) itemView.findViewById(R.id.text_time);

            itemView.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                   /* Toast.makeText(itemView.getContext(), "hi "
                            , Toast.LENGTH_SHORT).show();*/


    mActionMode = ((MainActivity)c).startActionMode(new       MyActionModeCallback());

                }
            });

            //Add Expand Area to a Card
            cardView = (CardView) itemView.findViewById(R.id.card_view);
            cardView.setRadius(0);

        }



    }



        CustomerListAdapter(List<ParseUser> customer){ // MyAdapter Constructor with titles and icons parameter
        // titles, icons, name, email, profile pic are passed from the main activity as we
       mCustomers=customer;



        //in adapter
    }



    @Override
    public CustomerListAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_row,parent,false); //Inflating the layout

            ViewHolder vhItem = new ViewHolder(v,viewType,context); //Creating ViewHolder and passing the object of type view

            return vhItem; // Returning the created object

            //inflate your layout and pass it to view holder
    }

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

        ParseUser  customer=mCustomers.get(position);
        holder.Name_fiedl.setText(customer.getString(ParseConstants.KEY_USER_REAL_NAME)); // Setting the Text with the array of our Titles
        holder.Number_ppl_field.setText(String.valueOf(customer.getInt(ParseConstants.KEY_CUSTOMER_NUMBER_PPL)));// Settimg the image with array of our icons
        String time=customer.getString(ParseConstants.KEY_CUSTOMER_TIME);
        SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy h:mm:ss a");
        SimpleDateFormat dateFormat2 = new SimpleDateFormat("hh:mm aa");
        try {
            Date date = dateFormat.parse(time);

             String out= dateFormat2.format(date);
            holder.Time_field.setText(out);
            //Log.e("Time", out);
        } catch (ParseException e) {
        }


        if(customer.getInt(ParseConstants.KEY_CUSTOMER_NUMBER_PPL)==3){
            holder.circleview.setImageResource(R.color.lightblue500);
        }
        else if(customer.getInt(ParseConstants.KEY_CUSTOMER_NUMBER_PPL)==4){
            holder.circleview.setImageResource(R.color.lightblue500);
        }
        else if(customer.getInt(ParseConstants.KEY_CUSTOMER_NUMBER_PPL)==5){
            holder.circleview.setImageResource(R.color.lightgreen500);
        }
        else if(customer.getInt(ParseConstants.KEY_CUSTOMER_NUMBER_PPL)>5){
            holder.circleview.setImageResource(R.color.lightgreen500);
        }

    }
    @Override
    public int getItemCount() {

        return mCustomers.size(); // the number of items in the list will be +1 the titles including the header view.
    }
    public void remove(String item) {
        int position = mCustomers.indexOf(item);
        mCustomers.remove(position);
        notifyItemRemoved(position);
    }
   }

class MyActionModeCallback implements ActionMode.Callback{


    @Override
    public boolean onCreateActionMode(ActionMode actionMode, Menu menu) {
        actionMode.getMenuInflater().inflate(R.menu.menu_login, menu);
        return false;
    }

    @Override
    public boolean onPrepareActionMode(ActionMode actionMode, Menu menu) {
        actionMode.setTitle("hihi");
        return false;
    }

    @Override
    public boolean onActionItemClicked(ActionMode actionMode, MenuItem menuItem) {
        return false;
    }

    @Override
    public void onDestroyActionMode(ActionMode actionMode) {

    }
}

在我的适配器中：

CustomerListAdapter(List < ParseUser > customer, Activity Activity)
{ // MyAdapter Constructor with titles and icons parameter
    // titles, icons, name, email, profile pic are passed from the main activity as we
    mCustomers = customer;
    mActivity= Activity;


    //in adapter
} 

但我仍然面临错误，显示非静态字段不能应用于静态字段

这里：

mActionMode = ((MainActivity)c).startActionMode(new MyActionModeCallback());

上下文的

c

对象可能为空

要在

CustomerListAdapter

类中获取活动上下文，请使用类构造函数：

private Acivity mActivity;

public CustomerListAdapter(Activity mActivity){
  this.mActivity=mActivity;
  ....
}

使用

mActivity

从活动调用

startActionMode

方法：

 mActionMode = mActivity.startActionMode(new MyActionModeCallback());

在创建

CustomerListAdapter

class对象时，使用

this

从

MainActivity

传递活动上下文：

CustomerListAdapter adapter=new CustomerListAdapter(this);

活跃

 public class Main extends AppCompatActivity {
     public Toolbar toolbar;
    AdapterEXT mAdapter;
    .....
     @Override
        protected void onCreate(Bundle savedInstanceState) {
     toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);
            assert getSupportActionBar() != null;
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            getSupportActionBar().setDisplayShowHomeEnabled(true);
    ......
     List<DataXXX> data = new ArrayList<>();
     mAdapter = new AdapterEXT(Main.this , toolbar, data);

---

你能提供一些上下文的周围代码吗？嗨，我已经添加了一些关于适配器的代码class@user3818938：可能

c

为

null

ya，有什么我可以解决的吗？@user3818938:show

CustomerListAdapter

classcode@user3818938：使用适配器的单独类实现我的应答，在私人活动方面，我有点困惑；公共CustomerListAdapter（Activity mActivity）{this.mActivity=mActivity；…}@user3818938:为什么要混淆？在CustomerListAdapter中添加构造函数，如我的回答中所示。我已编辑了该问题。我想我们快到了。只需要解决非静态问题issue@user3818938：将

mActivity

声明为

static

或从

ViewHolder

类中删除

static

 mActionMode = mActivity.startActionMode(new MyActionModeCallback());

CustomerListAdapter adapter=new CustomerListAdapter(this);

 public class Main extends AppCompatActivity {
     public Toolbar toolbar;
    AdapterEXT mAdapter;
    .....
     @Override
        protected void onCreate(Bundle savedInstanceState) {
     toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);
            assert getSupportActionBar() != null;
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            getSupportActionBar().setDisplayShowHomeEnabled(true);
    ......
     List<DataXXX> data = new ArrayList<>();
     mAdapter = new AdapterEXT(Main.this , toolbar, data);

 class AdapterEXT extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
        public Context context;
        public Toolbar toolbar;
     AdapterEXT (Context context, Toolbar toolbar, List<DataXXX> dataXXX) {
             this.context = context;
            this.toolbar=toolbar;
            this.dataXXX = dataXXX;
        }

toolbar.setTitle(context.getString(R.string.YourTXTfromXML));