Android模拟器学framework和driver之battery & backlight-----8. backlight in framework

前面我们已经从linux kernel一直介绍到了android jni，现在我们来看看更上层的封装，代码位置：

/frameworks/base/services/java/com/android/server/LightsService.java

这里其实就是封装了一个setLight函数，我们来看下，首先是load我们jni中的接口：

[java]
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private static native int init_native();
private static native void finalize_native(int ptr);

private static native void setLight_native(int ptr, int light, int color, int mode,
int onMS, int offMS, int brightnessMode);

private final Context mContext;

private int mNativePointer;

[java]
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LightsService(Context context) {

mNativePointer = init_native();
mContext = context;

ServiceManager.addService("hardware", mLegacyFlashlightHack);

for (int i = 0; i < LIGHT_ID_COUNT; i++) {
mLights[i] = new Light(i);
}
}

LightsService(Context context) {

mNativePointer = init_native();
mContext = context;

ServiceManager.addService("hardware", mLegacyFlashlightHack);

for (int i = 0; i < LIGHT_ID_COUNT; i++) {
mLights[i] = new Light(i);
}
}

这里只是把闪光灯的服务加到了系统的service中，我们这里没有，只有backlight，所以我们不关心，关心的之后下面这个for循环，这里只是new了一个light对象而已，其中当然包括我们的背光了。

我们来跟踪下我们的native 函数在哪被调用了，查看了下只有一个地方：

[java]
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private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode) {
if (color != mColor || mode != mMode || onMS != mOnMS || offMS != mOffMS) {
mColor = color;
mMode = mode;
mOnMS = onMS;
mOffMS = offMS;
setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);
}
}

private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode) {
if (color != mColor || mode != mMode || onMS != mOnMS || offMS != mOffMS) {
mColor = color;
mMode = mode;
mOnMS = onMS;
mOffMS = offMS;
setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);
}
}

就是这个函数，这个setLightLocked函数可以说是这边的一个接口吧，在上层的都调用了这个函数，来设置背光的，下面的可以自己分析。