我在真正的Nexus 5设备Android 6.0.1中观察到以下奇怪的结果
我在推出应用程序时运行以下简单代码。
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，上面的代码工作正常。它返回非空数组。
但是，当我更改targetSdkVersion并使用
defaultConfig {
applicationId "org.yccheok.myapplication"
minSdkVersion 19
targetSdkVersion 23
versionCode 1
versionName "1.0"
}
以上代码返回0长度数组！
在针对targetSdkVersion=23进行编译时，知道为什么会出现问题。
请注意，在产生问题期间，无论何时更改targetSdkVersion并通过Android Studio运行，您都需要清除应用数据，清除应用缓存并手动卸载所有用户。< /强>
以下是在Nexus 5设备Android 6.0.1中重现问题的步骤
<?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>
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'
}
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0长度数组
答案 0 :(得分：3)
GET_ACCOUNTS是dangerous permission，当使用目标sdk 23时，需要使用runtime permissions进行管理，否则无效。
您需要在运行时从用户实际request permission。 例如：
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详细了解了这一点。
危险权限涵盖应用程序需要涉及用户私人信息的数据或资源的区域，或者可能会影响用户存储的数据或其他应用程序的操作。例如，读取用户联系人的权限是一种危险的权限。如果应用声明它需要危险权限，则用户必须明确授予该应用的权限。