2018-2019安卓系统总结

开发安卓系统，有一些特殊需求，修改系统源码比较普遍，下面说说

需求一：屏蔽按键和触摸功能【物理按键】，但是模拟按键是可以操作【自动化操作】，组合键取消屏蔽

思路：作为系统都知道PhoneWindowManager PWM是最终处理按键的结果，但是在模拟按键处理上，也会屏蔽掉，所以不合适在PWM服务进行处理，按键触摸流程是从kernel 按键值 和系统按键值 是有映射关系的，需要通过映射表进行转换，后面查询了按键流程【后续发表相关文章】 InputReader.cpp processEventsLocked 实时对驱动层上报按键的十六进制进行处理，最后决定在方法进行处理，这样不好影响模拟按键处理。这里有个属性 persist.sys.input.stop 系统属性进行判断是否要屏蔽按键和触摸，这里通过按一下电源键，2s内在按一下音量+键，取消屏蔽按键和触摸。

+long long startWhen;
 void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {
     for (const RawEvent* rawEvent = rawEvents; count;) {
+        int32_t isStopInputDevices;
+        isStopInputDevices = property_get_int32("persist.sys.input.stop", 0);
+        //ALOGD("processEventsLocked:isStopInputDevices=%d startWhen=%lld",isStopInputDevices,startWhen);
+        if(isStopInputDevices == 1){           
+          //power key
+          if((rawEvent->code == 0x0074) && (rawEvent->value ==0x00000000)){
+            ALOGD("--POWER up---");
+            startWhen = rawEvent->when;
+               }
+          //volumn up
+          else if(rawEvent->code == 0x0073 && (rawEvent->value ==0x00000001)){
+            ALOGD("--VOLUME_UP down---when=%lld",rawEvent->when - startWhen);
+            if( (rawEvent->when - startWhen) <=  2000000000){
+              property_set("persist.sys.input.stop", "0");
+            }
+          }
+          return;
+        }
         int32_t type = rawEvent->type;
         size_t batchSize = 1;
         if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {

需求二 安装普通第三方应用，默认授予权限【比如 摄像头 sd卡权限之类】

思路：安装应用 其实大家都知道PackageManagerService.java是由pms服务进行逻辑的处理的，要找到具体处理授权的方法grantPermissionsLPw

    private void grantPermissionsLPw(PackageParser.Package pkg, boolean replace,
            String packageOfInterest) {
        // IMPORTANT: There are two types of permissions: install and runtime.
        // Install time permissions are granted when the app is installed to
        // all device users and users added in the future. Runtime permissions
        // are granted at runtime explicitly to specific users. Normal and signature
        // protected permissions are install time permissions. Dangerous permissions
        // are install permissions if the app's target SDK is Lollipop MR1 or older,
        // otherwise they are runtime permissions. This function does not manage
        // runtime permissions except for the case an app targeting Lollipop MR1
        // being upgraded to target a newer SDK, in which case dangerous permissions
        // are transformed from install time to runtime ones.
        ......

        Slog.d(TAG, "--- grant permission ----" );
        //包名来默认确定授权
        if(pkg.packageName.contains("com.tencent.mm") ) {
            final int permsSize = pkg.requestedPermissions.size();
            for (int i=0; i

需求三，系统时间更新会不准确，有时候是1970时间点

思路：系统时间更新时候偶发是会出现不准确，但是要检查的时候，又是准确的，后面发现是ntp服务器配置返回的值是不可靠的，第一修改ntp 服务地址，第二 对获取时间毫秒进行验证，在进行设置时间【以上个更新时间为基准，进行判断】，这里persist.sys.ntp.time 系统属性是为了保存上个更新的时间点毫秒时间

@@ -46,6 +46,7 @@ import com.android.internal.util.DumpUtils;
 
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
+import android.os.SystemProperties;
 
 /**
  * Monitors the network time and updates the system time if it is out of sync
@@ -193,6 +194,11 @@ public class NetworkTimeUpdateService extends Binder {
             // only update when NTP time is fresh
             if (mTime.getCacheAge() < mPollingIntervalMs) {
                 final long ntp = mTime.currentTimeMillis();
+                long originNtp = SystemProperties.getLong("persist.sys.ntp.time", 0);
+                Log.d(TAG, "originNtp = " + originNtp+" ntp="+ntp);
+                if(originNtp > ntp){
+                   return;
+                }
                 mTryAgainCounter = 0;
                 // If the clock is more than N seconds off or this is the first time it's been
                 // fetched since boot, set the current time.
@@ -207,6 +213,8 @@ public class NetworkTimeUpdateService extends Binder {
                     // Make sure we don't overflow, since it's going to be converted to an int
                     if (ntp / 1000 < Integer.MAX_VALUE) {
                         SystemClock.setCurrentTimeMillis(ntp);
+                        SystemProperties.set("persist.sys.ntp.time", ntp+"");
+                        Log.d(TAG, "----setCurrentTimeMillis-----");
                     }
                 } else {
                     if (DBG) Log.d(TAG, "Ntp time is close enough = " + ntp);

需求四，应用白名单，限制应用安装

思路：根据应用的包名 和 版本号 进行限制安装

参考之前写的博客：https://blog.csdn.net/fmc088/article/details/80949812

需求五，ota升级

思路：第一在有系统的源码基础上，可以使用RecoverySystem.installPackageLegacy 接口进行ota升级，第二；如果第三方应用有root权限，某种意义上来说，echo -e  --update_package=path  > /cache/recovery/command  && reboot recovery 

参考博客：https://blog.csdn.net/fmc088/article/details/80400726