Android通过SystemProperties获取build.prop中配置的信息

其他 2018-07-06 20:46:55 阅读次数: 0

前言

        我们知道system.prop文件中存储着系统运行的很多配置信息（具体特定平台或产品的修改信息），system.prop文件中的内容最终会被编译到build.prop文件中，当程序运行时需要某种系统状态时，会到build.prop中进行读取。Android中提供了一个android.os.SystemProperties类来负责读取其中的内容，并且提供了几个Static的方法，可以让应用很方便地使用。

系统源码展示

  1. /*
  2. * Copyright (C) 2006 The Android Open Source Project
  3. *
  4. * Licensed under the Apache License, Version 2.0 (the "License");
  5. * you may not use this file except in compliance with the License.
  6. * You may obtain a copy of the License at
  7. *
  8. * http://www.apache.org/licenses/LICENSE-2.0
  9. *
  10. * Unless required by applicable law or agreed to in writing, software
  11. * distributed under the License is distributed on an "AS IS" BASIS,
  12. * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13. * See the License for the specific language governing permissions and
  14. * limitations under the License.
  15. */
  17. package android.os;
  19. import java.util.ArrayList;
  22. /**
  23. * Gives access to the system properties store. The system properties
  24. * store contains a list of string key-value pairs.
  25. *
  26. * {@hide}
  27. */
  28. public class SystemProperties
  29. {
  30. public static final int PROP_NAME_MAX = 31;
  31. public static final int PROP_VALUE_MAX = 91;
  33. private static final ArrayList<Runnable> sChangeCallbacks = new ArrayList<Runnable>();
  35. private static native String native_get(String key);
  36. private static native String native_get(String key, String def);
  37. private static native int native_get_int(String key, int def);
  38. private static native long native_get_long(String key, long def);
  39. private static native boolean native_get_boolean(String key, boolean def);
  40. private static native void native_set(String key, String def);
  41. private static native void native_add_change_callback();
  43. /**
  44. * Get the value for the given key.
  45. * @return an empty string if the key isn't found
  46. * @throws IllegalArgumentException if the key exceeds 32 characters
  47. */
  48. public static String get(String key) {
  49. if (key.length() > PROP_NAME_MAX) {
  50. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  51. }
  52. return native_get(key);
  53. }
  55. /**
  56. * Get the value for the given key.
  57. * @return if the key isn't found, return def if it isn't null, or an empty string otherwise
  58. * @throws IllegalArgumentException if the key exceeds 32 characters
  59. */
  60. public static String get(String key, String def) {
  61. if (key.length() > PROP_NAME_MAX) {
  62. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  63. }
  64. return native_get(key, def);
  65. }
  67. /**
  68. * Get the value for the given key, and return as an integer.
  69. * @param key the key to lookup
  70. * @param def a default value to return
  71. * @return the key parsed as an integer, or def if the key isn't found or
  72. * cannot be parsed
  73. * @throws IllegalArgumentException if the key exceeds 32 characters
  74. */
  75. public static int getInt(String key, int def) {
  76. if (key.length() > PROP_NAME_MAX) {
  77. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  78. }
  79. return native_get_int(key, def);
  80. }
  82. /**
  83. * Get the value for the given key, and return as a long.
  84. * @param key the key to lookup
  85. * @param def a default value to return
  86. * @return the key parsed as a long, or def if the key isn't found or
  87. * cannot be parsed
  88. * @throws IllegalArgumentException if the key exceeds 32 characters
  89. */
  90. public static long getLong(String key, long def) {
  91. if (key.length() > PROP_NAME_MAX) {
  92. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  93. }
  94. return native_get_long(key, def);
  95. }
  97. /**
  98. * Get the value for the given key, returned as a boolean.
  99. * Values 'n', 'no', '0', 'false' or 'off' are considered false.
  100. * Values 'y', 'yes', '1', 'true' or 'on' are considered true.
  101. * (case sensitive).
  102. * If the key does not exist, or has any other value, then the default
  103. * result is returned.
  104. * @param key the key to lookup
  105. * @param def a default value to return
  106. * @return the key parsed as a boolean, or def if the key isn't found or is
  107. * not able to be parsed as a boolean.
  108. * @throws IllegalArgumentException if the key exceeds 32 characters
  109. */
  110. public static boolean getBoolean(String key, boolean def) {
  111. if (key.length() > PROP_NAME_MAX) {
  112. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  113. }
  114. return native_get_boolean(key, def);
  115. }
  117. /**
  118. * Set the value for the given key.
  119. * @throws IllegalArgumentException if the key exceeds 32 characters
  120. * @throws IllegalArgumentException if the value exceeds 92 characters
  121. */
  122. public static void set(String key, String val) {
  123. if (key.length() > PROP_NAME_MAX) {
  124. throw new IllegalArgumentException( "key.length > " + PROP_NAME_MAX);
  125. }
  126. if (val != null && val.length() > PROP_VALUE_MAX) {
  127. throw new IllegalArgumentException( "val.length > " +
  128. PROP_VALUE_MAX);
  129. }
  130. native_set(key, val);
  131. }
  133. public static void addChangeCallback(Runnable callback) {
  134. synchronized (sChangeCallbacks) {
  135. if (sChangeCallbacks.size() == 0) {
  136. native_add_change_callback();
  137. }
  138. sChangeCallbacks.add(callback);
  139. }
  140. }
  142. static void callChangeCallbacks() {
  143. synchronized (sChangeCallbacks) {
  144. //Log.i("foo", "Calling " + sChangeCallbacks.size() + " change callbacks!");
  145. if (sChangeCallbacks.size() == 0) {
  146. return;
  147. }
  148. ArrayList<Runnable> callbacks = new ArrayList<Runnable>(sChangeCallbacks);
  149. for ( int i= 0; i<callbacks.size(); i++) {
  150. callbacks.get(i).run();
  151. }
  152. }
  153. }
  154. }

工具类源码展示

      因为SystemProperties.java类已被系统隐藏，因此我们通过Java反射机制获取该类内容，通过get和set方法来读取、设置build.prop里面的内容。

  1. package com.mufeng.testproject.tools;
  3. import android.content.Context;
  4. import android.util.Log;
  6. import java.io.File;
  7. import java.io.IOException;
  8. import java.lang.reflect.Method;
  10. import dalvik.system.DexFile;
  12. /**
  13. * Created by zhangqing on 2017/3/1.
  14. */
  15. public class SystemPropertiesProxy {
  16. public static final String TAG = "SystemPropertiesProxy";
  18. /**
  19. * 根据给定的Key返回String类型的值
  20. *
  21. * @param context 上下文
  22. * @param key 获取指定信息所需的key
  23. * @return 返回一个String类型的值，如果不存在该key则返回空字符串
  24. */
  25. public static String getString(Context context, String key) {
  26. String result = "";
  27. try {
  28. ClassLoader classLoader = context.getClassLoader();
  29. @SuppressWarnings( "rawtypes")
  30. Class SystemProperties = classLoader.loadClass( "android.os.SystemProperties");
  31. //参数类型
  32. @SuppressWarnings( "rawtypes")
  33. Class[] paramTypes = new Class[ 1];
  34. paramTypes[ 0] = String.class;
  35. Method getString = SystemProperties.getMethod( "get", paramTypes);
  36. //参数
  37. Object[] params = new Object[ 1];
  38. params[ 0] = new String(key);
  40. result = (String) getString.invoke(SystemProperties, params);
  41. } catch (IllegalArgumentException e) {
  42. //e.printStackTrace();
  43. //如果key超过32个字符则抛出该异常
  44. Log.w(TAG, "key超过32个字符");
  45. } catch (Exception e) {
  46. result = "";
  47. }
  48. return result;
  49. }
  51. /**
  52. * 根据给定的Key返回String类型的值
  53. *
  54. * @param context 上下文
  55. * @param key 获取指定信息所需的key
  56. * @param def key不存在时的默认值
  57. * @return 返回一个String类型的值，如果key不存在, 并且如果def不为null则返回def,否则返回空字符串
  58. */
  59. public static String getString(Context context, String key, String def) {
  60. String result = def;
  61. try {
  62. ClassLoader classLoader = context.getClassLoader();
  63. @SuppressWarnings( "rawtypes")
  64. Class SystemProperties = classLoader.loadClass( "android.os.SystemProperties");
  65. //参数类型
  66. @SuppressWarnings( "rawtypes")
  67. Class[] paramTypes = new Class[ 2];
  68. paramTypes[ 0] = String.class;
  69. paramTypes[ 1] = String.class;
  70. Method getString = SystemProperties.getMethod( "get", paramTypes);
  71. //参数
  72. Object[] params = new Object[ 2];
  73. params[ 0] = new String(key);
  74. params[ 1] = new String(def);
  76. result = (String) getString.invoke(SystemProperties, params);
  77. } catch (IllegalArgumentException e) {
  78. //e.printStackTrace();
  79. //如果key超过32个字符则抛出该异常
  80. Log.w(TAG, "key超过32个字符");
  81. } catch (Exception e) {
  82. result = def;
  83. }
  84. return result;
  85. }
  87. /**
  88. * 根据给定的key返回int类型的值
  89. *
  90. * @param context 上下文
  91. * @param key 要查询的key
  92. * @param def 默认返回值
  93. * @return 返回一个int类型的值，如果没有发现则返回默认值 def
  94. */
  95. public static Integer getInt(Context context, String key, int def) {
  96. Integer result = def;
  97. try {
  98. ClassLoader classLoader = context.getClassLoader();
  99. @SuppressWarnings( "rawtypes")
  100. Class SystemProperties = classLoader.loadClass( "android.os.SystemProperties");
  101. //参数类型
  102. @SuppressWarnings( "rawtypes")
  103. Class[] paramTypes = new Class[ 2];
  104. paramTypes[ 0] = String.class;
  105. paramTypes[ 1] = int.class;
  106. Method getInt = SystemProperties.getMethod( "getInt", paramTypes);
  107. //参数
  108. Object[] params = new Object[ 2];
  109. params[ 0] = new String(key);
  110. params[ 1] = new Integer(def);
  111. result = (Integer) getInt.invoke(SystemProperties, params);
  112. } catch (IllegalArgumentException e) {
  113. //e.printStackTrace();
  114. //如果key超过32个字符则抛出该异常
  115. Log.w(TAG, "key超过32个字符");
  116. } catch (Exception e) {
  117. result = def;
  118. }
  119. return result;
  120. }
  122. /**
  123. * 根据给定的key返回long类型的值
  124. *
  125. * @param context 上下文
  126. * @param key 要查询的key
  127. * @param def 默认返回值
  128. * @return 返回一个long类型的值，如果没有发现则返回默认值def
  129. */
  130. public static Long getLong(Context context, String key, long def) {
  131. Long result = def;
  132. try {
  133. ClassLoader classLoader = context.getClassLoader();
  134. @SuppressWarnings( "rawtypes")
  135. Class SystemProperties = classLoader.loadClass( "android.os.SystemProperties");
  136. //参数类型
  137. @SuppressWarnings( "rawtypes")
  138. Class[] paramTypes = new Class[ 2];
  139. paramTypes[ 0] = String.class;
  140. paramTypes[ 1] = long.class;
  141. Method getLong = SystemProperties.getMethod( "getLong", paramTypes);
  142. //参数
  143. Object[] params = new Object[ 2];
  144. params[ 0] = new String(key);
  145. params[ 1] = new Long(def);
  146. result = (Long) getLong.invoke(SystemProperties, params);
  147. } catch (IllegalArgumentException e) {
  148. //e.printStackTrace();
  149. //如果key超过32个字符则抛出该异常
  150. Log.w(TAG, "key超过32个字符");
  151. } catch (Exception e) {
  152. result = def;
  153. }
  154. return result;
  155. }
  157. /**
  158. * 根据给定的key返回boolean类型的值
  159. * 如果值为'n','no','0','false' or 'off'返回false
  160. * 如果值为'y','yes','1','true' or 'on'返回true
  161. * 如果key不存在, 或者是其它的值, 则返回默认值
  162. *
  163. * @param context 上下文
  164. * @param key 要查询的key
  165. * @param def 默认返回值
  166. * @return 返回一个boolean类型的值，如果没有发现则返回默认值def
  167. */
  168. public static Boolean getBoolean(Context context, String key, boolean def) {
  169. Boolean result = def;
  170. try {
  171. ClassLoader classLoader = context.getClassLoader();
  172. @SuppressWarnings( "rawtypes")
  173. Class SystemProperties = classLoader.loadClass( "android.os.SystemProperties");
  174. //参数类型
  175. @SuppressWarnings( "rawtypes")
  176. Class[] paramTypes = new Class[ 2];
  177. paramTypes[ 0] = String.class;
  178. paramTypes[ 1] = boolean.class;
  179. Method getBoolean = SystemProperties.getMethod( "getBoolean", paramTypes);
  180. //参数
  181. Object[] params = new Object[ 2];
  182. params[ 0] = new String(key);
  183. params[ 1] = new Boolean(def);
  184. result = (Boolean) getBoolean.invoke(SystemProperties, params);
  185. } catch (IllegalArgumentException e) {
  186. //e.printStackTrace();
  187. //如果key超过32个字符则抛出该异常
  188. Log.w(TAG, "key超过32个字符");
  189. } catch (Exception e) {
  190. result = def;
  191. }
  192. return result;
  193. }
  195. /**
  196. * 根据给定的key和值设置属性, 该方法需要特定的权限才能操作.
  197. *
  198. * @param context 上下文
  199. * @param key 设置属性的key
  200. * @param val 设置属性的value
  201. */
  202. public static void set(Context context, String key, String val) {
  203. try {
  204. @SuppressWarnings( "rawtypes")
  205. DexFile df = new DexFile( new File( "/system/app/Settings.apk"));
  206. ClassLoader classLoader = context.getClassLoader();
  207. @SuppressWarnings( "rawtypes")
  208. Class SystemProperties = Class.forName( "android.os.SystemProperties");
  209. //参数类型
  210. @SuppressWarnings( "rawtypes")
  211. Class[] paramTypes = new Class[ 2];
  212. paramTypes[ 0] = String.class;
  213. paramTypes[ 1] = String.class;
  214. Method set = SystemProperties.getMethod( "set", paramTypes);
  215. //参数
  216. Object[] params = new Object[ 2];
  217. params[ 0] = new String(key);
  218. params[ 1] = new String(val);
  219. set.invoke(SystemProperties, params);
  220. } catch (IllegalArgumentException e) {
  221. //e.printStackTrace();
  222. //如果key超过32个字符或者value超过92个字符则抛出该异常
  223. Log.w(TAG, "key超过32个字符或者value超过92个字符");
  224. } catch (Exception e) {
  225. e.printStackTrace();
  226. }
  227. }
  228. }

猜你喜欢

转载自blog.csdn.net/xiaozhude/article/details/80915356
今日推荐
基于大语言模型的开源知识库问答系统 MaxKB GitHub Star 数量突破 5,000 个！
美国拟限制 AI 大模型出口中国和俄罗斯
苹果将与 OpenAI 达成协议，将 ChatGPT 应用于 iPhone
openKylin 社区生态委员会第六次会议圆满召开
阿里云正式发布通义千问 2.5
Python 3.13 发布首个 Beta：实验性自由线程模式和 JIT、改进交互式解释器
Stack Overflow 拿我的代码去训练 AI 大模型，还封了我的账号
Pop!_OS 的 COSMIC 桌面完成 App Store 上架工作
报告：Django 仍然是 74% 开发者的首选
《2024 年一季度互联网投融资运行情况》研究报告
15 年前上了“FFmpeg 耻辱柱”，今天他还得谢谢咱——腾讯QQPlayer一雪前耻？
TIOBE 5 月榜单：Fortran “复活”进入 Top 10
周排行
BPM为企业带来的实际利益
好程序员web前端分享css常用属性缩写
Java文件下载（excel）
css样式的动态添加及显示和隐藏等零碎用法
axios全局配置以及拦截器
使用Logstash来实时同步MySQL和log日志数据到ES
C++获取当前时间（年月日、时分秒、毫秒）
Odoo产品分析 (四) -- 工具板块(11) -- 网站即时聊天(1)
Java环境配置正确，但是java、javac、java -version均返回“不是内部或外部命令，也不是可运行的程序或批处理文件”？
01 官网下载各种CentOS教程（超详细版）
每日归档
更多
2024-05-14(0)
2024-05-13(18)
2024-05-12(0)
2024-05-11(38)
2024-05-10(38)
2024-05-09(35)
2024-05-08(42)
2024-05-07(14)
2024-05-06(40)
2024-05-05(0)

代码天地 © 2018 codetd.com

境外服务器   最新电视剧2022