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：

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  @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

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  /** * 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：

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  @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()）；

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  /** * 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；

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/** * {@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);