本示例使用的发卡器：https://item.taobao.com/item.htm?id=615391857885&spm=a1z10.5-c.w4002-21818769070.11.1f60789ey1EsPH

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:padding="3dp"tools:context=".NdefURLActivity"><androidx.appcompat.widget.Toolbarandroid:id="@+id/toolbar"android:layout_width="match_parent"android:layout_height="30dp"android:background="?attr/colorPrimary"app:navigationIcon="@drawable/baseline_arrow_back_ios_24"app:titleTextColor="@color/white"tools:ignore="MissingConstraints"tools:layout_editor_absoluteY="0dp"><TextViewandroid:id="@+id/TextViewlabelDispleft"android:layout_width="wrap_content"android:layout_height="match_parent"android:text="返回"android:textColor="@color/white"android:textSize="16sp"android:gravity="center"android:onClick="retmain" /><TextViewandroid:id="@+id/TextViewlabelDisp"android:layout_width="match_parent"android:layout_height="match_parent"android:text="NDEF_URL  "android:textColor="@color/white"android:textSize="16sp"android:gravity="center_horizontal|right|center"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="@+id/TextViewlabelDispleft"app:layout_constraintTop_toTopOf="parent" /></androidx.appcompat.widget.Toolbar><TextViewandroid:id="@+id/sample_text"android:layout_width="fill_parent"android:layout_height="150dp"android:padding="3dp"android:text="操作结果"android:textSize="12sp"android:background="@drawable/shape4border"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintBottom_toBottomOf="parent"/><ScrollViewandroid:id="@+id/scrollViewIC"android:layout_width="fill_parent"android:layout_height="0dp"android:layout_marginBottom="5dp"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toBottomOf="@+id/toolbar"app:layout_constraintBottom_toTopOf="@+id/sample_text"android:scrollbars="horizontal"><androidx.constraintlayout.widget.ConstraintLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:padding="3dp"         ><TextViewandroid:id="@+id/textlabletitle"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginTop="10dp"android:text="标题:"android:textSize="16sp"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toTopOf="parent" /><EditTextandroid:id="@+id/Edittexttitle"android:layout_width="350dp"android:layout_height="wrap_content"android:textSize="16sp"android:gravity="left"android:hint="百度"app:layout_constraintBottom_toBottomOf="@+id/textlabletitle"app:layout_constraintLeft_toRightOf="@+id/textlabletitle"app:layout_constraintTop_toTopOf="@+id/textlabletitle" /><TextViewandroid:id="@+id/textlableprefix"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginTop="10dp"android:text="前缀:"android:textSize="16sp"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toBottomOf="@+id/textlabletitle" /><Spinnerandroid:id="@+id/spin_Selurlprefix"android:layout_width="350dp"android:layout_height="wrap_content"android:entries="@array/NdefUrlPrefix"android:theme="@style/my_spinner_style"app:layout_constraintBottom_toBottomOf="@+id/textlableprefix"app:layout_constraintLeft_toRightOf="@+id/textlableprefix"app:layout_constraintTop_toTopOf="@+id/textlableprefix" /><EditTextandroid:id="@+id/edittexturl"android:layout_width="match_parent"android:layout_height="80dp"android:layout_marginLeft="38dp"android:layout_marginTop="10dp"android:background="@drawable/shape4border"android:gravity="left"android:inputType="textCapCharacters"android:maxLines="8"android:hint="baidu.com"android:textSize="12sp"app:layout_constraintLeft_toRightOf="@+id/textlableprefix"app:layout_constraintTop_toBottomOf="@+id/spin_Selurlprefix" /><Buttonandroid:id="@+id/butt_writeurltag"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginTop="8dp"android:text="将以上URL写入标签"android:textSize="14sp"android:onClick="writeurltag"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toBottomOf="@+id/edittexturl" /></androidx.constraintlayout.widget.ConstraintLayout></ScrollView></androidx.constraintlayout.widget.ConstraintLayout>

package com.usbreadertest;import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;import androidx.appcompat.app.AppCompatActivity;import com.reader.ourmifare;public class NdefURLActivity extends AppCompatActivity {private TextView tv;private Spinner ctrselefix;private EditText ctrtitle;private EditText ctrurlinf;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_ndef_url);androidx.appcompat.widget.Toolbar toolbar=findViewById(R.id.toolbar);setSupportActionBar(toolbar);tv = findViewById(R.id.sample_text);tv.setText("操作结果");ctrselefix=findViewById(R.id.spin_Selurlprefix);ctrselefix.setSelection(2);ctrurlinf=findViewById(R.id.edittexturl);ctrurlinf.requestFocus();ctrtitle=findViewById(R.id.Edittexttitle);}@Overridepublic void onBackPressed(){super.onBackPressed();finish();}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {if(item.getItemId()==android.R.id.home){finish();return true;}return super.onOptionsItemSelected(item);}public void retmain(View view){finish();}public void writeurltag(View view)  throws Exception  {String languagecodestr="en";byte[] languagecodebyte= languagecodestr.getBytes("gb2312");int languagecodestrlen=languagecodebyte.length;String urltstr=ctrurlinf.getText().toString().trim();if(urltstr.length()<1){tv.setText("请输入要写入的网址！");ctrurlinf.requestFocus();return;}byte[] urlbyte=urltstr.getBytes();int  urllen=urlbyte.length;String titletstr=ctrtitle.getText().toString().trim();byte[] titlebyte=titletstr.getBytes();int titlelen=titlebyte.length;byte urlheaderindex = (byte)(ctrselefix.getSelectedItemId());ourmifare.tagbufclear();    //先清空NDEF数据缓冲byte status=ourmifare.tagbufadduri(languagecodebyte,languagecodestrlen,titlebyte,titlelen,urlheaderindex,urlbyte,urllen);   //生成NDEF数据缓冲if (status==0){int tagtype=NdefTextActivity.CheckCardType();    //检测发卡器上标签类型if(tagtype==-1){tv.setText("发卡器感应区未发现有效的NDEF标签！");return;}byte[] mypiccserial=new byte[8];status=NdefTextActivity.WriteTag(tagtype,mypiccserial);   //将已生成的NDEF数据写入不同的标签内String dispinfo=NdefTextActivity.dispwritetag(status ,mypiccserial,tagtype);tv.setText(dispinfo);}}
}

源码下载：AndroidstudioRFIDNFC读写源码资源-CSDN文库