android - targetSdkVersion 23通过accountManager.getAccounts()返回长度为0的数组

我在真正的Nexus 5设备Android 6.0.1中观察到以下奇怪结果

在我的应用启动期间，我运行以下简单代码。

Pattern emailPattern = Patterns.EMAIL_ADDRESS; // API level 8+
AccountManager accountManager = AccountManager.get(this);
Account[] accounts = accountManager.getAccounts();

如果我将targetSdkVersion设置为22、21、19，则上面的代码可以正常工作。它返回非空数组。

但是，当我更改targetSdkVersion并进行测试时

defaultConfig {
    applicationId "org.yccheok.myapplication"
    minSdkVersion 19
    targetSdkVersion 23
    versionCode 1
    versionName "1.0"
}

上面的代码返回长度为0的数组!

对targetSdkVersion=23进行编译时，为什么事情会中断的任何想法。

请注意，在产生问题的过程中，每当更改targetSdkVersion并通过Android Studio运行它时，都需要清除应用程序数据，清除应用程序缓存并手动为所有用户卸载。

以下是在Nexus 5设备Android 6.0.1中重现该问题的步骤

通过File-> New-> New Projetct在Android Studio中创建项目。

选择“空白 Activity ”

AndroidManifest.xml

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

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

    <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"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId "org.yccheok.myapplication"
        minSdkVersion 19
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
}

MainActivity.java

import android.accounts.Account;
import android.accounts.AccountManager;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Patterns;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

import java.util.regex.Pattern;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        int targetSdkVersion = 0;
        try {
            PackageInfo packageInfo = getPackageManager().getPackageInfo(getPackageName(), 0);
            targetSdkVersion = packageInfo.applicationInfo.targetSdkVersion;
        }
        catch (PackageManager.NameNotFoundException e) {
            android.util.Log.i("CHEOK", e.getMessage());
        }

        Pattern emailPattern = Patterns.EMAIL_ADDRESS; // API level 8+
        AccountManager accountManager = AccountManager.get(this);
        Account[] accounts = accountManager.getAccounts();

        android.util.Log.i("CHEOK", targetSdkVersion + " : numnber of accoutn by ??? = " + accounts.length);

        for (Account account : accounts) {
            if (emailPattern.matcher(account.name).matches()) {
                String possibleEmail = account.name;
                android.util.Log.i("CHEOK", "possibleEmail = " + possibleEmail);
            }
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

知道为什么targetSdkVersion 23通过accountManager.getAccounts()返回长度为0的数组

最佳答案

GET_ACCOUNTS是dangerous permission，使用目标sdk 23时需要使用runtime permissions进行管理，否则它将不起作用。

您实际上需要在运行时从用户获取request permission。
例子:

      ActivityCompat.requestPermissions(this, new String[]
      {Manifest.permission.GET_ACCOUNTS}, 1);

      int permissionCheck = ContextCompat.checkSelfPermission(thisActivity,
      Manifest.permission.GET_ACCOUNTS);

我已经在this answer here中对此进行了详细介绍。