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：

<?xml version="1.0" encoding="utf-8"?><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：

<?xml version="1.0" encoding="utf-8"?><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

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