该实验是通过ContentProvider读取手机通讯录

知识点包含了RecyclerView控件、UriMatcher、ContentResolver

先看效果，显示手机通讯录

 首先是界面的布局代码

activity_main59.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity59">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#42BCF3"
        android:gravity="center"
        android:text="通讯录"
        android:textColor="#FFFFFF"
        android:textSize="30dp" />

    <androidx.recyclerview.widget.RecyclerView

        android:id="@+id/rv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#E4E0E0"
        />
</LinearLayout>

其次是RecyclerView的item布局代码，其中使用了CardView是为了方便快捷的弄个圆角储来

main59_item.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:padding="40dp"
    app:cardCornerRadius="40px"
    android:layout_marginTop="20dp"
    android:background="@color/white">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/txlogo"/>
    <LinearLayout
        android:layout_marginLeft="10dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="姓名"
            android:textSize="20dp"
            android:textStyle="bold" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="号码"
            android:layout_marginTop="10dp"
            android:id="@+id/number"
            android:textSize="20dp"/>
    </LinearLayout>
    </LinearLayout>

</androidx.cardview.widget.CardView>

一个联系人的实体类

Communication

public class Communication {
    private  String name;
    private String number;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public Communication(String name, String number) {
        this.name = name;
        this.number = number;
    }
}

RecyclerView的适配器：

Main59Adapter

import android.content.Context;
import android.database.Cursor;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;

import org.jetbrains.annotations.NotNull;

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

public class Main59Adapter extends RecyclerView.Adapter<Main59Adapter.MyViewHolder> {

    private  RecyclerView mRv;
    private Context context;
    private List<Communication> dataSource;


    public Main59Adapter(Context context,RecyclerView recyclerView){
        this.context=context;
        this.dataSource=new ArrayList<>();
        this.mRv=recyclerView;
    }
    public void setDataSource(List<Communication> dataSource) {
        this.dataSource = dataSource;
        notifyDataSetChanged();
    }


    class  MyViewHolder extends RecyclerView.ViewHolder{

        TextView name,number;
        public MyViewHolder(@NonNull @NotNull View itemView) {
            super(itemView);
            name=itemView.findViewById(R.id.name);
            number=itemView.findViewById(R.id.number);
        }
    }

    @NonNull
    @NotNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull @NotNull ViewGroup parent, int viewType) {
        return new Main59Adapter.MyViewHolder(LayoutInflater.from(context).inflate(R.layout.main59_item,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull @NotNull MyViewHolder holder, int position) {
        holder.name.setText(dataSource.get(position).getName());
        holder.number.setText(dataSource.get(position).getNumber());

    }

    @Override
    public int getItemCount() {
        return dataSource.size();
    }
}

逻辑代码

MainActivity59

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.view.View;
import android.view.ViewGroup;

import org.jetbrains.annotations.NotNull;

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

public class MainActivity59 extends AppCompatActivity {
/*
* ContentProvider
* 我们想在自己的应用中访问别的应用，或者说一些ContentProvider暴露给我们的一些数据， 比如手机联系人，短信等！我们想对这些数据进行读取或者修改，这就需要用到ContentProvider了
* 我们自己的应用，想把自己的一些数据暴露出来，给其他的应用进行读取或操作，我们也可以用 到ContentProvider，另外我们可以选择要暴露的数据，就避免了我们隐私数据的的泄露
* 并不仅仅可以查数据，根据权限 还能增删改数据
* */
    RecyclerView recyclerView;
    Cursor cursor;
    List<Communication>communications=new ArrayList<>();
    private  Main59Adapter mAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main59);
        //动态申请权限
        getContacts();
        recyclerView=findViewById(R.id.rv);
        LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
        mAdapter=new Main59Adapter(this,recyclerView);

        recyclerView.setAdapter(mAdapter);
        mAdapter.setDataSource(communications);

    }


//获取手机联系人
    private void getContacts(){
        //①查询raw_contacts表获得联系人的id
        ContentResolver resolver = getContentResolver();
        Uri uri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;
        //查询联系人数据
        cursor = resolver.query(uri, null, null, null, null);
        cursor.moveToFirst();
       do
        {
            //获取联系人姓名,手机号码
            String cName = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
            String cNum = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
            communications.add(new Communication(cName,cNum));
        }while (cursor.moveToNext());
        cursor.close();
    }



}

另外请注意在AndroidManifest.xml

添加权限：

    <uses-permission android:name="android.permission.READ_CONTACTS" /> <!-- 手机联系人 -->

可以翻看资料进行静态或动态申请，也可以直接进行手机系统将手机通讯录权限给APP

这里给出一个例子:

点击按钮没有权限申请权限，有权限跳转通讯录界面，注意：这只是个例子需要你修改，

一般报错如下是这个原因：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mk.zhengtailai.PersonalBankManager/com.mk.zhengtailai.PersonalBankManager. TXLActivity}: java.lang.SecurityException: Permission Denial: opening provider com.android.providers.contacts. ContactsProvider2 from ProcessRecord{85e7d40 8538:com.mk.zhengtailai. PersonalBankManager/u0a124} (pid=8538, uid=10124) requires android.permission. READ_CONTACTS or android.permission.WRITE_CONTACTS

 view.findViewById(R.id.button5).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(ContextCompat.checkSelfPermission(getContext(), Manifest.permission.READ_CONTACTS)
                        != PackageManager.PERMISSION_GRANTED){
                    ActivityCompat.requestPermissions(getActivity(),new String[]{Manifest.permission.READ_CONTACTS},1);
                }else {
                    Intent intent=new Intent(getContext(),TXLActivity.class);
                    startActivity(intent);
                }
            }
        });

今天又写了一遍发现，手机没有通讯录的话会报错：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mk.zhengtailai.PersonalBankManager/com.mk.zhengtailai.PersonalBankManager. TXLActivity}: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0

所以我就随便加个try处理一下：

 try {
         Intent intent=new Intent(getContext(),TXLActivity.class);
         startActivity(intent);
      }catch (Exception e){
          Toast.makeText(getContext(), "通讯录无联系人", Toast.LENGTH_SHORT).show();
       }