ContextMenu高级用法

关键字： ContextMenu

背景

我们经常在列表的页面中，点击列表中的行，一般进入详情页面，长按列表中一行，会弹出一个菜单，包含了对某一行的操作（编辑、删除等等），也知道通常的用法：

• 0x01. 在Activity中注册需要上下文菜单的View：
  registerForContextMenu(mListView);
• 0x02. 然后在Activity中继承onCreateContextMenu方法，添加菜单项：

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {    
Log.d(LOG_TAG, "onCreateContextMenu");    
super.onCreateContextMenu(menu, v, menuInfo);    
menu.setHeaderTitle(R.string.prompt);    
menu.add(Menu.NONE, R.id.context_menu_item_delete_record, Menu.NONE, R.string.delete_record);//groupId, itemId, order, title    
menu.add(Menu.NONE, R.id.context_menu_item_delete_record_with_file, Menu.NONE, R.string.delete_record_with_file);
}```
 **PS：每次长按出现上下文菜单都会调用这个方法**

/** * Called when a context menu for the {@code view} is about to
be shown. * Unlike {@link #onCreateOptionsMenu(Menu)}, this will
be called every * time the context menu is about to be shown and
should be populated for * the view (or item inside the view for {@link
AdapterView} subclasses, * this can be found in the {@code
menuInfo})). *

* Use {@link #onContextItemSelected(android.view.MenuItem)} to know when an

• item has been selected. *

  * It is not safe to hold onto the
  context menu after this method returns. * */
  public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
  }

 - 0x03. 接下来长按列表中一行的时候，会弹出上下文菜单：
![device-2015-11-04-141103.png](http://upload-images.jianshu.io/upload_images/728306-c1f997a517d009c7.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
 - 0x04. 点击菜单后，在Activity中继承onContextItemSelected方法进行处理：

@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()){
}
}

 - 0x05. 获取Item标识（id）
 我们删除数据库或者一行记录的时候，要知道主键（一般是id）才能进行操作，很多人就想办法，有的是把ListView的每个ItemView添加一个LongClickListener，然后长按的时候记录下Position，然后在进行相应处理。
    
    其实有更优雅的做法，onContextItemSelected(MenuItem item)回调的参数item可以获取item.getMenuInfo()，在ListView和Adapter的模式中，可以强制转换成AdapterContextMenuInfo，拿到targetView（即所长按行的ItemVew，如果我们需要什么参数，直接放到View.setTag中去即可）：

AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
int index = info.position;
View view = info.targetView;

至此，常见的用法就完了，那么遇到其他自定义View呢？
 - 0x06. 自定义View的ContextMenu实现
下面以用到的RecycleView为例，没有了ListView及其Adapter的封装，我们需要自己处理ContextMenu。
最重要的是继承View的两个方法：
1.上下文菜单Item的附加信息（上面item.getMenuInfo()）；

/** * Views should implement this if they have extra information to
associate * with the context menu. The return result is supplied as a
parameter to * the {@link
OnCreateContextMenuListener#onCreateContextMenu(ContextMenu,
View, ContextMenuInfo)} * callback. * * @return Extra information
about the item for which the context menu * should be shown.
This information will vary across different * subclasses of View. */
protected ContextMenuInfo getContextMenuInfo() {
return null;
}

2.ViewGroup的showContextMenuForChild，每次弹出上下文菜单都会调用此方法，需要在这里更新ContextMenuInfo；

/** * {@inheritDoc} */
public boolean showContextMenuForChild(View originalView) {
return mParent != null && mParent.showContextMenuForChild(originalView);
}

 - 0x07. 自定义RecycleView的ContextMenu全部代码

package com.lbrant.phone.view;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.ContextMenu;
import android.view.View;

/**

• 作者：dell

• 时间：2015/11/3 18:34

• 文件：PhoneRecorder

• 描述：
  */
  public class ContextMenuRecyclerView extends RecyclerView {
  private static final String LOG_TAG = "ContextMenuRecyclerView";
  private RecyclerContextMenuInfo mContextMenuInfo = new RecyclerContextMenuInfo();

  public ContextMenuRecyclerView(Context context) {
  super(context);
  }

  public ContextMenuRecyclerView(Context context, AttributeSet attrs) {
  super(context, attrs);
  }

  public ContextMenuRecyclerView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  }

  @Override
  protected ContextMenu.ContextMenuInfo getContextMenuInfo() {
  return mContextMenuInfo;
  }

  @Override
  public boolean showContextMenuForChild(View originalView) {
  Log.d(LOG_TAG, "showContextMenuForChild");
  Object tag = originalView.getTag();
  if (tag instanceof RecyclerItemMarker) {
  mContextMenuInfo.mRecycleItemMarker = (RecyclerItemMarker) tag;
  }

   return super.showContextMenuForChild(originalView);
  

  }

  public static class RecyclerItemMarker {
  public final int position;
  public final Object obj;

   public RecyclerItemMarker(int position, Object obj) {
       this.position = position;
       this.obj = obj;
   }
  

  }

  public static class RecyclerContextMenuInfo implements ContextMenu.ContextMenuInfo {
  public RecyclerItemMarker mRecycleItemMarker;
  }
  }

  private class RecordRecycleViewAdapter extends RecyclerView.Adapter {
  private Cursor mCallRecordCursor;
  private int mIdIndex;
  private int mPhoneNumberIndex;
  private int mCallTimeIndex;
  private int mDurationIndex;
  private int mPathIndex;

   public RecordRecycleViewAdapter(Cursor cursor) {
       mCallRecordCursor = cursor;
       updateCursorColumnIndex();
   }
  
   private void updateCursorColumnIndex() {
       if (mCallRecordCursor != null) {
           mIdIndex = mCallRecordCursor.getColumnIndex(BaseDatabaseHelper.RECORDS_COLUMNS._ID);
           mPhoneNumberIndex = mCallRecordCursor.getColumnIndex(BaseDatabaseHelper.RECORDS_COLUMNS.NUMBER);
           mCallTimeIndex = mCallRecordCursor.getColumnIndex(BaseDatabaseHelper.RECORDS_COLUMNS.CALL_TIME);
           mDurationIndex = mCallRecordCursor.getColumnIndex(BaseDatabaseHelper.RECORDS_COLUMNS.DURATION);
           mPathIndex = mCallRecordCursor.getColumnIndex(BaseDatabaseHelper.RECORDS_COLUMNS.PATH);
       }
   }
  
   @Override
   public RecordRecycleViewAdapter.RecordViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
       View contentView = LayoutInflater.from(parent.getContext()).inflate(R.layout.record_list_item, parent, false);
       RecordViewHolder viewHolder = new RecordViewHolder(contentView);
       return viewHolder;
   }
  
   @Override
   public void onBindViewHolder(RecordRecycleViewAdapter.RecordViewHolder holder, final int position) {
       holder.itemView.setLongClickable(true);
       if (mCallRecordCursor != null && mCallRecordCursor.moveToPosition(position)) {
           long id = mCallRecordCursor.getLong(mIdIndex);
           String phoneNumber = mCallRecordCursor.getString(mPhoneNumberIndex);
           long seconds = mCallRecordCursor.getLong(mDurationIndex);
           String callTime = mCallRecordCursor.getString(mCallTimeIndex);
           String path = mCallRecordCursor.getString(mPathIndex);
           String duration = String.format("%1$02d:%2$02d:%3$02d", seconds / 3600, seconds % 3600 / 60, seconds % 60);
  
           RecordInfo info = new RecordInfo();
           info.setId(id);
           info.setPhoneNumber(phoneNumber);
           info.setSecondsDuration(seconds);
           info.setCallTime(callTime);
           info.setPath(path);
  
           holder.itemView.setTag(new ContextMenuRecyclerView.RecyclerItemMarker(position, info));
           holder.mTextViewPhoneNumber.setText(phoneNumber);
           holder.mTextViewDuration.setText(duration);
           holder.mTextviewCallTime.setText(callTime);
  
           Cursor cursor = queryContactByPhoneNumber(ContactsContract.CommonDataKinds.Phone.NUMBER + " = '" + phoneNumber + "'");
           if (cursor != null) {
               if (cursor.moveToNext()) {
                   long contactId = cursor.getInt(0);
                   Cursor contactCursor = queryContact(ContactsContract.Contacts._ID + "=" + contactId);
                   if (contactCursor != null) {
                       holder.mTextViewName.setText(contactCursor.getString(1));
                       contactCursor.close();
                   }
               }
               cursor.close();
           }
       }
   }
  
   @Override
   public void onViewRecycled(RecordViewHolder holder) {
       super.onViewRecycled(holder);
       holder.itemView.setOnCreateContextMenuListener(null);
   }
  
   @Override
   public int getItemCount() {
       return mCallRecordCursor == null ? 0 : mCallRecordCursor.getCount();
   }
  
   public void changeCursor(Cursor cursor) {
       if (cursor != mCallRecordCursor) {
           if (mCallRecordCursor != null) {
               mCallRecordCursor.close();
           }
           mCallRecordCursor = cursor;
           updateCursorColumnIndex();
           notifyDataSetChanged();
       }
   }
  
   public class RecordViewHolder extends RecyclerView.ViewHolder {
       private ImageView mImageViewAvatar;
       private TextView mTextViewPhoneNumber;
       private TextView mTextViewName;
       private TextView mTextviewCallTime;
       private TextView mTextViewDuration;
  
       public RecordViewHolder(View itemView) {
           super(itemView);
           mImageViewAvatar = (ImageView) itemView.findViewById(R.id.imageViewAvatar);
           mTextViewName = (TextView) itemView.findViewById(R.id.textViewName);
           mTextViewPhoneNumber = (TextView) itemView.findViewById(R.id.textViewPhoneNumber);
           mTextviewCallTime = (TextView) itemView.findViewById(R.id.textViewCallTime);
           mTextViewDuration = (TextView) itemView.findViewById(R.id.textViewDuration);
       }
   }
  

  }

**有两个地方需要注意：**
1.onBindViewHolder中给ItemView添加Tag;
2.设置ItemView的LongClickable为true，不然不会出现上下文菜单（具体原因见ContextMenu原理分析）；
holder.itemView.setLongClickable(true);