android - 为什么工作上下文操作模式启动 ActionMode 不适用于参数的错误(ActionMode

Question

我正在学习教程 11. Exercise: Using the contextual action mode

但是我有这个错误:

mActionMode = Display.this.startActionMode(mActionModeCallback);
                view.setSelected(true);

  Error:  The method startActionMode(ActionMode.Callback) in the type Activity is not applicable for the arguments (ActionMode.Callback)

我检查了这个stackoverflow answer他们说要添加

 ActionBarActivity activity=(ActionBarActivity)getActivity();
activity.startSupportActionMode(modeCallBack);

我有这个错误

The method getActivity() is undefined for the type Display

我做错了什么？下面是我的代码。

package com.example.sqlfirst;


import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBar.Tab;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.view.ActionMode;
import android.view.ActionMode.Callback;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;


public class Display extends ActionBarActivity {
    private final static String TAG = "MainActivity";
    protected Object mActionMode;
    @Override 
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.grid_main);
         //have to use getSupportActionBar from android.support.v7.app
       // ActionBar actionBar = getSupportActionBar();
        //getActionBar().setDisplayHomeAsUpEnabled(true);

        ActionBarActivity activity=(ActionBarActivity)getActivity();
        activity.startSupportActionMode(modeCallBack);

          View view = findViewById(R.id.gridview);
            view.setOnLongClickListener(new View.OnLongClickListener() {
              // called when the user long-clicks on someView
              public boolean onLongClick(View view) {
                if (mActionMode != null) {
                  return false;
                }

                // start the CAB using the ActionMode.Callback defined above
                mActionMode = Display.this.startActionMode(mActionModeCallback);
                view.setSelected(true);
                return true;
              }
            });






        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new ImageAdapter(this));

        gridview.setOnItemClickListener(new OnItemClickListener() {

   public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            // Send intent to SingleViewActivity
       Intent i = new Intent(getApplicationContext(), SingleViewActivity.class);
       // Pass image index
       i.putExtra("id", position);
       startActivity(i);
       } });

        }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
         MenuInflater inflater = getMenuInflater();
            inflater.inflate(R.menu.activity_main_actions, menu);
        return super.onCreateOptionsMenu(menu);
    }

       public boolean onOptionsItemSelected(MenuItem item) 
       { 
          super.onOptionsItemSelected(item); 

     switch (item.getItemId()){

     case R.id.ic_action_person:
         Toast.makeText(this, "Create a new account please", Toast.LENGTH_SHORT).show();
           Intent intent = new Intent(this, Register.class);
             startActivity(intent);
         return true;

     case R.id.ic_action_search:

         Toast.makeText(this, "Search for new images", Toast.LENGTH_SHORT).show();
         Intent  isearch= new Intent(this,Search.class);
            startActivity(isearch);
     return true;

     case R.id.ic_action_picture:
         Toast.makeText(this, "Search for new photos", Toast.LENGTH_SHORT).show();
         Intent  iphotos= new Intent(this,Display.class);
         startActivity(iphotos);
         return true;


     }
        return true;
       } 



       private ActionMode.Callback mActionModeCallback = new ActionMode.Callback() {

         // Called when the action mode is created; startActionMode() was called
         public boolean onCreateActionMode(ActionMode mode, Menu menu) {
           // inflate a menu resource providing context menu items
           MenuInflater inflater = mode.getMenuInflater();
           // assumes that you have "contexual.xml" menu resources
           inflater.inflate(R.menu.activity_main_actions, menu);
           return true;
         }

         // called each time the action mode is shown. Always called after
         // onCreateActionMode, but
         // may be called multiple times if the mode is invalidated.
         public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
           return false; // Return false if nothing is done
         }

         // called when the user selects a contextual menu item
         public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
           switch (item.getItemId()) {
           case R.id.ic_action_picture:
             Toast.makeText(Display.this, "Selected menu",
                 Toast.LENGTH_LONG).show();
             mode.finish(); // Action picked, so close the CAB
             return true;
           default:
             return false;
           }
         }

         // called when the user exits the action mode
         public void onDestroyActionMode(ActionMode mode) {
           mActionMode = null;
         }
       };

}

Answer 1

您的 Display 类正在扩展 ActionBarActivity，这意味着它是一个 Activity，因此无需使用 getActivity()，您可以直接使用如下方法:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    /* this method is available within your ActionBarActivity*/
    startSupportActionMode(modeCallBack); 
    setContentView(R.layout.grid_main);

    // The rest of your code comes here
}