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ConxtMenu高级用法

##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})). * <p> * Use {@link #onContextItemSelected(android.view.MenuItem)} to know when an 
* item has been selected. * <p> * 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：

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）：
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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

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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<RecordRecycleViewAdapter.RecordViewHolder> {
        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);

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原文地址：https://www.cnblogs.com/lijianming180/p/12360983.html