Change value in Android console, code read value and switch branch.
In console
$ setprop rw.SECOND_DISPLAY_CONNECTED 0
In CPP code
property_get("rw.SECOND_DISPLAY_CONNECTED", value, "");
In Java code
import android.os.SystemProperties; ... int value= SystemProperties.getInt("rw.SECOND_DISPLAY_CONNECTED",0);
The SystemProperties definition in "~/myandroid/frameworks/base/core/java/android/os/SystemProperties.java"
public class SystemProperties { public static final int PROP_NAME_MAX = 31; public static final int PROP_VALUE_MAX = 91; private static native String native_get(String key); private static native String native_get(String key, String def); private static native int native_get_int(String key, int def); private static native long native_get_long(String key, long def); private static native boolean native_get_boolean(String key, boolean def); private static native void native_set(String key, String def); /** * 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(String key) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } return native_get(key); } /** * 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(String key, String def) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } return native_get(key, 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 * @throws IllegalArgumentException if the key exceeds 32 characters */ public static int getInt(String key, int def) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } return native_get_int(key, 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 * @throws IllegalArgumentException if the key exceeds 32 characters */ public static long getLong(String key, long def) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } return native_get_long(key, 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 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(String key, boolean def) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } return native_get_boolean(key, def); } /** * 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(String key, String val) { if (key.length() > PROP_NAME_MAX) { throw new IllegalArgumentException("key.length > " + PROP_NAME_MAX); } if (val != null && val.length() > PROP_VALUE_MAX) { throw new IllegalArgumentException("val.length > " + PROP_VALUE_MAX); } native_set(key, val); } }
From the code above, we can know when we call SystemProperties.getInt(), it will excute "int native_get_int(String key, int def)" .
