Where is android.os.SystemProperties?

Question

I'm looking at the Android Camera code, and when I try importing android.os.SystemProperties, it cannot be found.

Here is the file I'm looking at:
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.com and SystemProperties was not listed.

Did I miss something?

Answer 1

If you use the "reflection" option, you may use the class below

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
        }

    }
}

Answer 2

This is the class in the Android source code:

https://android.googlesource.com/platform/frameworks/base/+/eclair-release/core/java/android/os/SystemProperties.java

See {@hide} in the class JavaDoc? That means this class won't be exported as part of the public SDK.

The camera app uses it as it's internal and they won't use the public SDK to build it.

You may still be able to get at this class

1. by reflection or

2. by getting the source, removing @hide and making your own customized 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.