Android内容提供者之读取联系人信息

创建一个内容提供者：
在创建一个内容提供者时，首先需要定义一个类继承android.content包下的ContentProvider类。ContentProvider类是一个抽象类，在使用该类时需要重写它的onCreate(), delete(), getType(), insert(), query(), update()这几个抽象方法。
注册内容提供者
ContentProvider是Android的四大组件之一，因此需要和Activity一样在清单中注册。

案例——读取联系人信息
通过代码实现，得到以下界面

1.创建程序

读取联系人信息程序对定的布局文件(activity_main.xml)如下所示：

<RelativeLayout 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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="cn.edu.bzu.casemessagesend.MainActivity">

    <LinearLayout
        android:id="@+id/layoutPhonechoose"
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">
        <EditText
            android:id="@+id/etPhone"
            android:inputType="phone"
            android:background="@android:drawable/edit_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:layout_weight="1"
            android:hint="请输入联系人的电话号码"
            >
            <requestFocus>requestFocus>
            EditText>
        <ImageButton
            android:id="@+id/btnAdd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="selectContact"
            android:src="@drawable/plus"
            android:background="@null"

            />
    LinearLayout>

    <EditText
        android:id="@+id/etMsgContent"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:lines="8"
        android:inputType="textMultiLine"
        android:ems="10"
        android:layout_below="@id/layoutPhonechoose"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="19dp"
        android:hint="请输入短信内容"
         />

    <ImageButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/send"
        android:background="@null"
        android:layout_below="@+id/etMsgContent"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:id="@+id/imageButton" />


RelativeLayout>

2.ListView Item UI 界面
本案例用到了ListView来展示获取的数据，因此需要在res/layout的目录下创建一个activity_selectcontact文件，编写Item的布局。并需要在drawable下添加一张名为pilu.png的图片。代码如下：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_selectcontact"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="cn.edu.bzu.casemessagesend.SelectContactActivity">

    <TextView
        android:id="@+id/tvChooseContact"
        android:text="请选择联系人"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:textSize="24sp"
        android:textStyle="normal|bold" />

    <ListView
        android:id="@+id/lvContacts"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/tvChooseContact"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="18dp" />
RelativeLayout>

3.编写界面交互代码（MainActivity）

package cn.edu.bzu.casemessagesend;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void selectContact(View view){
        Intent intent=new Intent(this,SelectContactActivity.class);
        startActivity(intent);
    }
}

4.创建SelectContactActivity类继承AppCompatActivity

package cn.edu.bzu.casemessagesend;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.util.List;

import cn.edu.bzu.casemessagesend.uitl.ContactUtil;

public class SelectContactActivity extends AppCompatActivity {
    private ListView lvContacts;
    private List contacts;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_selectcontact);
        lvContacts=(ListView)findViewById(R.id.lvContacts);
        showContacts();
    }


    private void showContacts() {
        // Check the SDK version and whether the permission is already granted or not.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && checkSelfPermission(Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED ) {
            requestPermissions(new String[]{Manifest.permission.READ_CONTACTS}, 1);
            //After this point you wait for callback in onRequestPermissionsResult(int, String[], int[]) overriden method
        } else {
            // Android version is lesser than 6.0 or the permission is already granted.
            contacts =ContactUtil.getContacts(this);
            ArrayAdapter adapter=new ArrayAdapter(this,android.R.layout.simple_list_item_1,contacts);
            lvContacts.setAdapter(adapter);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions,  int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            showContacts();
        } else {
            Toast.makeText(this, "Until you grant the permission, we canot display the names", Toast.LENGTH_SHORT).show();
        }

    }
}

5.创建数据库。在util下创建ContactUtil

package cn.edu.bzu.casemessagesend.uitl;

import android.app.Activity;
import android.database.Cursor;
import android.provider.ContactsContract;

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

/**
 * Created by fengj on 2017/3/20.
 */
public class ContactUtil {
    public static List getContacts(Activity context) {
        Cursor cursor = null;
        List contacts = new ArrayList<>();
        try {
            cursor = context.getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
            if (cursor != null) {
                while (cursor.moveToNext()) {
                    String displayName = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
                    String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
                    contacts.add(displayName + "\n" + number);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
        return contacts;
    }


}

6.清单文件的配置：

 <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            intent-filter>
        activity>
        <activity android:name=".SelectContactActivity">activity>
    application>

7.运行程序读取联系人