什么是android.util.Log＃println_native（）？ [英] What is in android.util.Log#println_native()?

问题描述

此处是 android.util.Log 源代码。

在最底层（第340行），什么是在方法中：

At the very bottom (line 340), what is in the method:

public static native int println_native(int bufID,
        int priority, String tag, String msg);

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我猜 println_native（ ）或多或少像它的 println（），只是与 int bufID 不同。

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i guess println_native() is more or less like its println(), just with an int bufID different.

但即使我得到了 println_native（）的代码，我仍然缺少 com .android.internal.os.RuntimeInit （第19行， import ）来模拟 android.util.Log 。

But even i got the codes of println_native(), i still lack com.android.internal.os.RuntimeInit (line 19, the import) to simulate android.util.Log in old Android version.

推荐答案

刚刚在android源代码中进行了一些挖掘。此函数映射到

Just did some digging in the android source code. This function maps to

static jint android_util_Log_println_native(JNIEnv* env, jobject clazz,
    jint bufID, jint priority, jstring tagObj, jstring msgObj)
{
const char* tag = NULL;
const char* msg = NULL;

if (msgObj == NULL) {
    jniThrowNullPointerException(env, "println needs a message");
    return -1;
}

if (bufID < 0 || bufID >= LOG_ID_MAX) {
    jniThrowNullPointerException(env, "bad bufID");
    return -1;
}

if (tagObj != NULL)
    tag = env->GetStringUTFChars(tagObj, NULL);
msg = env->GetStringUTFChars(msgObj, NULL);

int res = __android_log_buf_write(bufID, (android_LogPriority)priority, tag, msg);

if (tag != NULL)
    env->ReleaseStringUTFChars(tagObj, tag);
env->ReleaseStringUTFChars(msgObj, msg);

return res;
}

基本上，这会将参数传递给系统中的驱动程序到日志缓冲区。 Linux内核中的 / dev / log 指向日志缓冲区。

Basically this then passes the arguments to the driver in the system which goes and writes to the Log buffer. Log buffer is pointed by /dev/log in the Linux kernel.

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