android.os.SystemProperties 在哪里？
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Where is android.os.SystemProperties?
提问by Travis
I'm looking at the Android Camera code, and when I try importing android.os.SystemProperties, it cannot be found.
我正在查看 Android 相机代码，当我尝试导入时android.os.SystemProperties，找不到它。
Here is the file I'm looking at:
https://android.googlesource.com/platform/packages/apps/Camera/+/eclair-release/src/com/android/camera/VideoCamera.java
这是我正在查看的文件：https:
//android.googlesource.com/platform/packages/apps/Camera/+/eclair-release/src/com/android/camera/VideoCamera.java
I created a new 2.1 project and tried importing this namespace again, but It still cannot be found. I checked https://developer.android.comand SystemPropertieswas not listed.
我创建了一个新的 2.1 项目并尝试再次导入此命名空间，但仍然找不到。我检查了https://developer.android.com并SystemProperties没有列出。
Did I miss something?
我错过了什么？
采纳答案by Jim Blackler
This is the class in the Android source code:
这是Android源代码中的类：
See {@hide}in the class JavaDoc? That means this class won't be exported as part of the public SDK.
{@hide}在 JavaDoc 类中看到了吗？这意味着此类不会作为公共 SDK 的一部分导出。
The camera app uses it as it's internal and they won't use the public SDK to build it.
相机应用程序使用它，因为它是内部的，他们不会使用公共 SDK 来构建它。
You may still be able to get at this class
你或许还能上这门课
by reflection or
by getting the source, removing
@hideand making your own customized SDK.
通过反思或
通过获取源、删除
@hide和制作您自己的自定义 SDK。
However pretty much by definition you are now going 'off SDK' and therefore your app may well be broken or get different behavior on OS versions as the Android folks will make little effort not to change this class between versions.
然而，根据定义，您现在正在使用 ' off SDK'，因此您的应用程序很可能会被破坏或在操作系统版本上出现不同的行为，因为 Android 人员几乎不会在版本之间更改此类。
回答by Void
If you use the "reflection" option, you may use the class below
如果您使用“反射”选项，您可以使用下面的类
package com.etc.etc;
import java.io.File;
import java.lang.reflect.Method;
import android.content.Context;
import dalvik.system.DexFile;
public class SystemPropertiesProxy
{
/**
* This class cannot be instantiated
*/
private SystemPropertiesProxy(){
}
/**
* Get the value for the given key.
* @return an empty string if the key isn't found
* @throws IllegalArgumentException if the key exceeds 32 characters
*/
public static String get(Context context, String key) throws IllegalArgumentException {
String ret= "";
try{
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties = cl.loadClass("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[1];
paramTypes[0]= String.class;
Method get = SystemProperties.getMethod("get", paramTypes);
//Parameters
Object[] params= new Object[1];
params[0]= new String(key);
ret= (String) get.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
ret= "";
//TODO
}
return ret;
}
/**
* Get the value for the given key.
* @return if the key isn't found, return def if it isn't null, or an empty string otherwise
* @throws IllegalArgumentException if the key exceeds 32 characters
*/
public static String get(Context context, String key, String def) throws IllegalArgumentException {
String ret= def;
try{
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties = cl.loadClass("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[2];
paramTypes[0]= String.class;
paramTypes[1]= String.class;
Method get = SystemProperties.getMethod("get", paramTypes);
//Parameters
Object[] params= new Object[2];
params[0]= new String(key);
params[1]= new String(def);
ret= (String) get.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
ret= def;
//TODO
}
return ret;
}
/**
* Get the value for the given key, and return as an integer.
* @param key the key to lookup
* @param def a default value to return
* @return the key parsed as an integer, or def if the key isn't found or
* cannot be parsed
* @throws IllegalArgumentException if the key exceeds 32 characters
*/
public static Integer getInt(Context context, String key, int def) throws IllegalArgumentException {
Integer ret= def;
try{
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties = cl.loadClass("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[2];
paramTypes[0]= String.class;
paramTypes[1]= int.class;
Method getInt = SystemProperties.getMethod("getInt", paramTypes);
//Parameters
Object[] params= new Object[2];
params[0]= new String(key);
params[1]= new Integer(def);
ret= (Integer) getInt.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
ret= def;
//TODO
}
return ret;
}
/**
* Get the value for the given key, and return as a long.
* @param key the key to lookup
* @param def a default value to return
* @return the key parsed as a long, or def if the key isn't found or
* cannot be parsed
* @throws IllegalArgumentException if the key exceeds 32 characters
*/
public static Long getLong(Context context, String key, long def) throws IllegalArgumentException {
Long ret= def;
try{
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties= cl.loadClass("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[2];
paramTypes[0]= String.class;
paramTypes[1]= long.class;
Method getLong = SystemProperties.getMethod("getLong", paramTypes);
//Parameters
Object[] params= new Object[2];
params[0]= new String(key);
params[1]= new Long(def);
ret= (Long) getLong.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
ret= def;
//TODO
}
return ret;
}
/**
* Get the value for the given key, returned as a boolean.
* Values 'n', 'no', '0', 'false' or 'off' are considered false.
* Values 'y', 'yes', '1', 'true' or 'on' are considered true.
* (case insensitive).
* If the key does not exist, or has any other value, then the default
* result is returned.
* @param key the key to lookup
* @param def a default value to return
* @return the key parsed as a boolean, or def if the key isn't found or is
* not able to be parsed as a boolean.
* @throws IllegalArgumentException if the key exceeds 32 characters
*/
public static Boolean getBoolean(Context context, String key, boolean def) throws IllegalArgumentException {
Boolean ret= def;
try{
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties = cl.loadClass("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[2];
paramTypes[0]= String.class;
paramTypes[1]= boolean.class;
Method getBoolean = SystemProperties.getMethod("getBoolean", paramTypes);
//Parameters
Object[] params= new Object[2];
params[0]= new String(key);
params[1]= new Boolean(def);
ret= (Boolean) getBoolean.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
ret= def;
//TODO
}
return ret;
}
/**
* Set the value for the given key.
* @throws IllegalArgumentException if the key exceeds 32 characters
* @throws IllegalArgumentException if the value exceeds 92 characters
*/
public static void set(Context context, String key, String val) throws IllegalArgumentException {
try{
@SuppressWarnings("unused")
DexFile df = new DexFile(new File("/system/app/Settings.apk"));
@SuppressWarnings("unused")
ClassLoader cl = context.getClassLoader();
@SuppressWarnings("rawtypes")
Class SystemProperties = Class.forName("android.os.SystemProperties");
//Parameters Types
@SuppressWarnings("rawtypes")
Class[] paramTypes= new Class[2];
paramTypes[0]= String.class;
paramTypes[1]= String.class;
Method set = SystemProperties.getMethod("set", paramTypes);
//Parameters
Object[] params= new Object[2];
params[0]= new String(key);
params[1]= new String(val);
set.invoke(SystemProperties, params);
}catch( IllegalArgumentException iAE ){
throw iAE;
}catch( Exception e ){
//TODO
}
}
}
回答by Jared Rummler
The class posted as an answer from user Void has a bunch of unnecessary things. Here is my class that uses reflection on android.os.SystemProperties:
作为用户 Void 的答案发布的课程有很多不必要的东西。这是我在android.os.SystemProperties上使用反射的类：
/*
* Copyright (C) 2015 Jared Rummler
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Gives access to the system properties store. The system properties store contains a list of
* string key-value pairs.
*/
public class SystemProperties {
private static final Class<?> SP = getSystemPropertiesClass();
/**
* Get the value for the given key.
*/
public static String get(String key) {
try {
return (String) SP.getMethod("get", String.class).invoke(null, key);
} catch (Exception e) {
return null;
}
}
/**
* Get the value for the given key.
*
* @return if the key isn't found, return def if it isn't null, or an empty string otherwise
*/
public static String get(String key, String def) {
try {
return (String) SP.getMethod("get", String.class, String.class).invoke(null, key, def);
} catch (Exception e) {
return def;
}
}
/**
* Get the value for the given key, returned as a boolean. Values 'n', 'no', '0', 'false' or
* 'off' are considered false. Values 'y', 'yes', '1', 'true' or 'on' are considered true. (case
* sensitive). If the key does not exist, or has any other value, then the default result is
* returned.
*
* @param key
* the key to lookup
* @param def
* a default value to return
* @return the key parsed as a boolean, or def if the key isn't found or is not able to be
* parsed as a boolean.
*/
public static boolean getBoolean(String key, boolean def) {
try {
return (Boolean) SP.getMethod("getBoolean", String.class, boolean.class)
.invoke(null, key, def);
} catch (Exception e) {
return def;
}
}
/**
* Get the value for the given key, and return as an integer.
*
* @param key
* the key to lookup
* @param def
* a default value to return
* @return the key parsed as an integer, or def if the key isn't found or cannot be parsed
*/
public static int getInt(String key, int def) {
try {
return (Integer) SP.getMethod("getInt", String.class, int.class).invoke(null, key, def);
} catch (Exception e) {
return def;
}
}
/**
* Get the value for the given key, and return as a long.
*
* @param key
* the key to lookup
* @param def
* a default value to return
* @return the key parsed as a long, or def if the key isn't found or cannot be parsed
*/
public static long getLong(String key, long def) {
try {
return (Long) SP.getMethod("getLong", String.class, long.class).invoke(null, key, def);
} catch (Exception e) {
return def;
}
}
private static Class<?> getSystemPropertiesClass() {
try {
return Class.forName("android.os.SystemProperties");
} catch (ClassNotFoundException shouldNotHappen) {
return null;
}
}
private SystemProperties() {
throw new AssertionError("no instances");
}
}
回答by danS
You could exec out to the getpropcommand:
您可以执行以下getprop命令：
String line = "";
try {
Process ifc = Runtime.getRuntime().exec("getprop ro.hardware");
BufferedReader bis = new BufferedReader(new InputStreamReader(ifc.getInputStream()));
line = bis.readLine();
} catch (java.io.IOException e) {
}
ifc.destroy();
回答by Cakey
After a lot of messing around I've finally got reflection code above working to both set and create new native system properties, there are some caveats:
经过一番折腾，我终于得到了上面的反射代码，可以设置和创建新的本机系统属性，但有一些注意事项：
You need to be the system user, add: android:sharedUserId="android.uid.system" to the manifest.
You need to sign your APK with the platform key, I cheated and just overrode the default debug signing key in eclipse as show here: http://stoned-android.blogspot.co.uk/2012_01_01_archive.html
The native system properties service has an ACL that controls all write access to properties you can subvert a key space (such as sys. or debug.). See /system/core/init/property_service.c:
{ "net.", AID_SYSTEM, 0 }, { "dev.", AID_SYSTEM, 0 }, { "runtime.", AID_SYSTEM, 0 }, { "hw.", AID_SYSTEM, 0 }, { "sys.", AID_SYSTEM, 0 }, { "service.", AID_SYSTEM, 0 }, { "wlan.", AID_SYSTEM, 0 }, { "dhcp.", AID_SYSTEM, 0 },
您需要是系统用户，在清单中添加： android:sharedUserId="android.uid.system"。
您需要使用平台密钥对您的 APK 进行签名，我作弊并覆盖了 eclipse 中的默认调试签名密钥，如下所示：http: //stoned-android.blogspot.co.uk/2012_01_01_archive.html
本机系统属性服务有一个 ACL，它控制对可以破坏键空间（例如 sys. 或 debug.）的属性的所有写访问。参见/system/core/init/property_service.c：
{ "net.", AID_SYSTEM, 0 }, { "dev.", AID_SYSTEM, 0 }, { "runtime.", AID_SYSTEM, 0 }, { "hw.", AID_SYSTEM, 0 }, { "sys.", AID_SYSTEM, 0 }, { "service.", AID_SYSTEM, 0 }, { "wlan.", AID_SYSTEM, 0 }, { "dhcp.", AID_SYSTEM, 0 },
Or if you are rolling your own build you could add your own key if you really wanted but it seems easier to reuse one of the above.
或者，如果您正在滚动自己的构建，则可以根据需要添加自己的密钥，但重用上述之一似乎更容易。
回答by khushank kashyap
After lots of searching I found a way to set the system property for Android. I was not able to find solution for Android Lollipop version. But I was successful in doing so. For setting system property we need to use :
经过大量搜索，我找到了一种为 Android 设置系统属性的方法。我无法找到适用于 Android Lollipop 版本的解决方案。但我这样做是成功的。为了设置系统属性，我们需要使用：
import android.os.SystemProperties
SystemProperties.set(key, value).
e.g. SystemProperties.set("sys.android", 5.0)
例如 SystemProperties.set("sys.android", 5.0)
Now you need to give permissions to the new system property
Go to /home/inkkashy04/Android_Lollypop/external/sepolicy/property_contextsand give suitable permission to your property
现在您需要为新的系统属性授予权限转到/home/inkkashy04/Android_Lollypop/external/sepolicy/property_contexts并为您的属性授予适当的权限
sys.android u:object_r:system_prop:s0
sys.android u:object_r:system_prop:s0
Now after flashing your image you can see your system properties listed by command:
现在，在刷新图像后，您可以看到通过命令列出的系统属性：
adb shell getprop
回答by Chulo
Gradle approach :
摇篮方法：
String SDK_DIR = System.getenv("ANDROID_SDK_HOME")
if(SDK_DIR == null) {
Properties props = new Properties()
props.load(new FileInputStream(project.rootProject.file("local.properties")))
SDK_DIR = props.get('sdk.dir');
}
dependencies {
compileOnly files("${SDK_DIR}/platforms/android-25/data/layoutlib.jar")
}
