Android读取手机通讯录联系人到自己项目

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical" 

 <ListView
  android:id="@+id/contacts_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent" 

 </ListView 
</LinearLayout 

public class MainActivity extends AppCompatActivity {

 ArrayAdapter<String  adapter;

 List<String  contactsList=new ArrayList< ();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  //获取到listview并且设置适配器
  ListView contactsView= (ListView) findViewById(R.id.contacts_view);
  adapter=new ArrayAdapter<String (this,android.R.layout.simple_list_item_1,contactsList);
  contactsView.setAdapter(adapter);

  //判断是否开启读取通讯录的权限
  if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS)!= PackageManager
    .PERMISSION_GRANTED){
   ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.READ_CONTACTS},1);
  }else {
   readContacts();
  }
 }

 private void readContacts() {
  Cursor cursor=null;
  try {
   //查询联系人数据,使用了getContentResolver().query方法来查询系统的联系人的数据
   //CONTENT_URI就是一个封装好的Uri，是已经解析过得常量
   cursor=getContentResolver().query(
     ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
     null,
     null,
     null,
     null
   );
   //对cursor进行遍历，取出姓名和电话号码
   if (cursor!=null){
    while (cursor.moveToNext()){
     //获取联系人姓名
     String displayName=cursor.getString(cursor.getColumnIndex(
       ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
     ));
     //获取联系人手机号
     String number=cursor.getString(cursor.getColumnIndex(
       ContactsContract.CommonDataKinds.Phone.NUMBER
     ));
     //把取出的两类数据进行拼接，中间加换行符，然后添加到listview中
     contactsList.add(displayName+"\n"+number);
    }
    //刷新listview
    adapter.notifyDataSetChanged();
   }
  }catch (Exception e){
   e.printStackTrace();
  }finally {
   //记得关掉cursor
   if (cursor!=null){
    cursor.close();
   }
  }
 }

 @Override
 public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
  switch (requestCode){
   case 1:
    if (grantResults.length 0&&grantResults[0]==PackageManager.PERMISSION_GRANTED){
     readContacts();
    }else {
     Toast.makeText(this,"没有权限",Toast.LENGTH_SHORT).show();
    }
    break;
   default:
    break;
  }
 }
}

<uses-permission android:name="android.permission.READ_CONTACTS"/