Android Studio初学者实例：ContentProvider读取手机通讯录

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

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

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 {
    private  RecyclerView mRv;
    private Context context;
    private List dataSource;
    public Main59Adapter(Context context,RecyclerView recyclerView){
        this.context=context;
        this.dataSource=new ArrayList();
        this.mRv=recyclerView;
    }
    public void setDataSource(List 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;
    Listcommunications=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：

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();
       }