BadgeView 一个可以自由定制外观、支持拖拽消除的 MaterialDesign 风格 Android BadgeView。
GitHub地址：https://github.com/stefanjauker/BadgeView
代码：

MainActivity：

package com.example.jash.badgeview;

import android.graphics.Color;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.DragEvent;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.jauker.widget.BadgeView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extendsAppCompatActivity {

private ViewPager pager;
    private FragmentPagerAdapter mAdapter;
    private List<Fragment> mDatas;
    private TextView FirstText;
    private TextView SecText;
    private TextView ThridText;
    private LinearLayout layout;
    private BadgeView badgeView;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pager =(ViewPager) findViewById(R.id.viewPager);
        initView();
        initText();
        badgeView.setOnDragListener(new View.OnDragListener() {
            @Override
            public boolean onDrag(View view, DragEvent dragEvent) {
                switch (dragEvent.getAction()) {
                }
                return false;
            }
        });
    }

private void initText() {
        FirstText = (TextView) findViewById(R.id.first);
        SecText = (TextView) findViewById(R.id.second);
        ThridText = (TextView) findViewById(R.id.thirid);
        layout =(LinearLayout) findViewById(R.id.first_layout);
    }

private void initView() {
        mDatas = new ArrayList<>();
        FirstFragment firstFragment = new FirstFragment();
        SecondFragment secondFragment = new SecondFragment();
        ThridFragment thridFragment = new ThridFragment();
        mDatas.add(firstFragment);
        mDatas.add(secondFragment);
        mDatas.add(thridFragment);
        mAdapter = new FragmentPagerAdapter(getSupportFragmentManager()){
            @Override
            public FragmentgetItem(int position) {
                return mDatas.get(position);
            }

@Override
            public int getCount() {
                return mDatas.size();
            }
        };
        pager.setAdapter(mAdapter);
        pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {

@Override
            public void onPageScrolled(int position, float positionOffset,int positionOffsetPixels) {

}

@Override
            public void onPageSelected(int position) {
                resetTextView();
                switch (position) {
                    case 0:
                        if (badgeView!= null) {
                            layout.removeView(badgeView);
                        }
                        badgeView = new BadgeView(MainActivity.this);
                        badgeView.setBadgeCount(20);
                        badgeView.setBadgeGravity(Gravity.BOTTOM | Gravity.RIGHT);
                        layout.addView(badgeView);
                        FirstText.setTextColor(Color.GREEN);
                        break;
                    case 1:
                        layout.removeView(badgeView);
                        SecText.setTextColor(Color.GREEN);
                        break;
                    case 2:
                        layout.removeView(badgeView);
                        ThridText.setTextColor(Color.GREEN);
                        break;
                }
            }

private void resetTextView() {
                FirstText.setTextColor(Color.BLACK);
                SecText.setTextColor(Color.BLACK);
                ThridText.setTextColor(Color.BLACK);
            }

@Override
            public void onPageScrollStateChanged(int state) {

}
        });
    }
}

mainXML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context="com.example.jash.badgeview.MainActivity"><include layout="@layout/top1" /><include layout="@layout/top2" /><android.support.v4.view.ViewPagerandroid:id="@+id/viewPager"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1" />
</LinearLayout>

Top1XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="50dp"android:background="#000"android:paddingLeft="12dp"android:paddingRight="12dp"><LinearLayoutandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerVertical="true"android:gravity="center"android:orientation="horizontal"><ImageViewandroid:layout_width="30dp"android:layout_height="30dp"android:src="@drawable/actionbar_icon" /><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="12dp"android:text="微信"android:textColor="#d3d3d3"android:textSize="18dp" /></LinearLayout><LinearLayoutandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentRight="true"android:layout_centerVertical="true"android:gravity="center"android:orientation="horizontal"><ImageViewandroid:layout_width="30dp"android:layout_height="30dp"android:src="@drawable/actionbar_search_icon" /><ImageViewandroid:layout_width="30dp"android:layout_height="30dp"android:src="@drawable/actionbar_add_icon" /><ImageViewandroid:layout_width="30dp"android:layout_height="30dp"android:src="@drawable/actionbar_more_icon" /></LinearLayout>
</RelativeLayout>

Top2XML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="40dp"android:background="#eee"android:orientation="vertical"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="37dp"android:orientation="horizontal"><LinearLayoutandroid:id="@+id/first_layout"android:orientation="horizontal"android:layout_width="0dp"android:layout_height="match_parent"android:layout_weight="1"android:gravity="center"><TextViewandroid:id="@+id/first"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="聊天"android:textColor="#0f0" /></LinearLayout><LinearLayoutandroid:layout_width="0dp"android:layout_height="match_parent"android:layout_weight="1"android:gravity="center"><TextViewandroid:id="@+id/second"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="发现"android:textColor="#000" /></LinearLayout><LinearLayoutandroid:layout_width="0dp"android:layout_height="match_parent"android:layout_weight="1"android:gravity="center"><TextViewandroid:id="@+id/thirid"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="通讯录"android:textColor="#000" /></LinearLayout></LinearLayout><ImageViewandroid:layout_width="match_parent"android:layout_height="3dp"android:background="@drawable/tabline" /></LinearLayout>

三个Fragment的Activity：

package com.example.jash.badgeview;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;/*** A simple {@link Fragment} subclass.*/
public class FirstFragment extends Fragment {public FirstFragment() {// Required empty public constructor}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {// Inflate the layout for this fragmentreturn inflater.inflate(R.layout.fragment_first, container, false);}}

Fragment的XML

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context="com.example.jash.badgeview.FirstFragment"><TextViewandroid:gravity="center"android:layout_width="match_parent"android:layout_height="match_parent"android:text="聊天" /></FrameLayout>

BadgeView的主要方法：
·       setTargetView(View) 
设置控件
·       setBadgeCount(int) 
设置显示的数字
·       setBadgeGravity(Gravity) 
设置显示的位置
·       setBackgroundColor() 
设置背景色
·       setBackgroundResource() 
设置背景图片
·       setTypeface() 
设置显示字体
·       setShadowLayer() 
设置字体阴影
·       setVisibility
设置显藏状态