相關知識

權限宣告與請求

CONTACTS 屬於危險權限，所以除了要在 AndroidManifest.xml 中宣告權限，還得在運行時請求權限許可。

ContentURI

存取 Contacts (聯絡人) 的 URI 為： ContactsContract.CommonDataKinds.Phone.*CONTENT_URI*

顯示名稱的欄位：ContactsContract.CommonDataKinds.Phone.*DISPLAY_NAME*

電話欄位：ContactsContract.CommonDataKinds.Phone.*NUMBER*

ContentResolver

這裏我們只會用到 ContentResolver 的 query() 功能，

val cursor = contentResolver.query(
    uri,           // ContentURI
    projection,    // 指定查詢的欄位名稱
    selection,     // 指定 WHERE 的條件
    selectionArgs, // 為 WHERE 的佔位符號提供實際值
    sortOrder)     // 指定資料排序

使用範例

// 查詢 todos 資料表的所有資料，取得所有欄位
val cursor = contentResolver.query(
    Uri.parse("content://app.kirin.android.provider/todos"),
		null,
    null,
    null,
    null)

while(cursor.moveToNext()) {
    val title = cursor.getString(cursor.getColumnIndex("title"))
}
cursor.close()

程式實作

建立含有一個 EmptyActivity 的專案: ContentResolver Lab

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="<http://schemas.android.com/apk/res/android>"
    package="app.kirin.android.contentresolverlab">

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

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

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

</manifest>

activity_main.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=".MainActivity">

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

</LinearLayout>

MainActivity.kt

package app.kirin.android.contentresolverlab

import android.Manifest
import android.annotation.SuppressLint
import android.content.pm.PackageManager
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.provider.ContactsContract
import android.widget.ArrayAdapter
import android.widget.ListView
import android.widget.Toast
import androidx.activity.result.contract.ActivityResultContracts
import androidx.core.content.ContextCompat

class MainActivity : AppCompatActivity() {

    private val contactsList = ArrayList<String>()
    private lateinit var adapter : ArrayAdapter<String>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, contactsList)
        val lvContacts = findViewById<ListView>(R.id.lv_contacts)
        lvContacts.adapter = adapter

        val permissionLauncher = registerForActivityResult(ActivityResultContracts.RequestPermission()) { result ->
            if (result) {
                showContacts()
            } else {
                Toast.makeText(this, "必須同意權限請求才能繼續使用", Toast.LENGTH_SHORT).show()
            }
        }
        if(ContextCompat.checkSelfPermission(
                this, Manifest.permission.READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) {
            showContacts()
        } else {
            permissionLauncher.launch(Manifest.permission.READ_CONTACTS)
        }
    }

    private fun showContacts() {
        contentResolver.query(
            ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
        null, null, null, null)?.apply {
            while(moveToNext()) {
                val displayName = getString(getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME))
                val number = getString(getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER))
                contactsList.add("$displayName\\n$number")
            }
            adapter.notifyDataSetChanged()
            close()
        }
    }
}