我正在查看 Android Camera 代码，当我尝试导入 android.os.SystemProperties 时，找不到。

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

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。我查了https://developer.android.com并且 SystemProperties 未列出。

我错过了什么吗？

最佳答案

如果你使用“反射”选项，你可以使用下面的类

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
        }

    }
}

关于android - android.os.SystemProperties 在哪里？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/2641111/