本篇主要實現了你可以自行控制從第一個字元開始進行聯想

public class AutoComplete extends AutoCompleteTextView {
    //輸入字元進行聯想，@163.com、@126.com、@qq.com、@sina.com、@yeah.net、@yahoo.com、@gmail.com等常用郵箱
    private static final String[] emailSuffix = {"@qq.com", "@163.com", "@126.com", "@gmail.com", "@sina.com", "@hotmail.com",
            "@yahoo.cn", "@sohu.com", "@foxmail.com", "@139.com", "@yeah.net", "@vip.qq.com", "@vip.sina.com"};

    public AutoComplete(Context context) {
        super(context);
        init(context);
    }

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

    private void init(Context context) {
        final MyAdatper adapter = new MyAdatper(context);
        setAdapter(adapter);
        addTextChangedListener(new TextWatcher() {
            @Override
            public void afterTextChanged(Editable s) {
                String input = s.toString();
                adapter.mList.clear();
                if (input.length() > 0) {
                    for (int i = 0; i < emailSuffix.length; ++i) {
                        adapter.mList.add(input + emailSuffix[i]);
                    }
                }
                adapter.notifyDataSetChanged();
                showDropDown();
            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count,
                                          int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before,
                                      int count) {
            }
        });
        // default=2 當輸入一個字元的時候就開始檢測
        setThreshold(1);
    }

    class MyAdatper extends BaseAdapter implements Filterable {
        List<String> mList;
        private Context mContext;
        private MyFilter mFilter;

        public MyAdatper(Context context) {
            mContext = context;
            mList = new ArrayList<String>();
        }

        @Override
        public int getCount() {
            return mList == null ? 0 : mList.size();
        }

        @Override
        public Object getItem(int position) {
            return mList == null ? null : mList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                TextView tv = new TextView(mContext);
                tv.setTextColor(Color.BLACK);
                tv.setTextSize(20);
                convertView = tv;
            }
            TextView txt = (TextView) convertView;
            txt.setText(mList.get(position));
            return txt;
        }

        @Override
        public Filter getFilter() {
            if (mFilter == null) {
                mFilter = new MyFilter();
            }
            return mFilter;
        }

        private class MyFilter extends Filter {

            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults results = new FilterResults();
                if (mList == null) {
                    mList = new ArrayList<String>();
                }
                results.values = mList;
                results.count = mList.size();
                return results;
            }

            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
                if (results.count > 0) {
                    notifyDataSetChanged();
                } else {
                    notifyDataSetInvalidated();
                }
            }
        }
    }
}

<fashion.test.com.email.AutoComplete
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

下面是實現的效果，可以看到可以監聽每一個字元