android ndk javah命令找不到Context或者Handler等sdk的class類

android ndk javah命令找不到Context或者Handler等sdk的class類

 

javah在ndk找不到Android相關的類

Android ndk開發的時候遇到了如果引用的class是Android的class，例如Context，Handler， Surface等Android sdk的類，javah就會找不到相關的類。

例如

package com.penny.demo;

import android.view.Surface;

public class MediaEntry {
    static {
        System.loadLibrary("native-lib");
    }

    public void setSurface(Surface surface) {
        native_setSurface(surface);
    }

    private native void native_setSurface(Surface surface);
}

如果我們運行javah生成jni文件時，就會面臨找不到Surface的問題

$ cd build/intermediates/javac/debug/compileDebugJavaWithJavac/classes/

$ javah -jni com.penny.demo.MediaEntry
Error: Class android.view.Surface could not be found.

這是因爲android.view.Surface是sdk裏面的類，並沒有在build/intermediates/javac/debug/compileDebugJavaWithJavac/classes/下面。

 

解決

解決這個問題很簡單，把Android.jar的路徑加入到javah classpath即可

1、 在macos和linux上運行

javah -jni -classpath $ANDROID_HOME/platforms/android-28/android.jar:. com.penny.demo.MediaEntry

於是命令運行成功

com_penny_demo_MediaEntry.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_penny_demo_MediaEntry */

#ifndef _Included_com_penny_demo_MediaEntry
#define _Included_com_penny_demo_MediaEntry
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_penny_demo_MediaEntry
 * Method:    native_setSurface
 * Signature: (Landroid/view/Surface;)V
 */
JNIEXPORT void JNICALL Java_com_penny_demo_MediaEntry_native_1setSurface
  (JNIEnv *, jobject, jobject);

#ifdef __cplusplus
}
#endif
#endif

2、在windows下命令

linux和macos運行命令畢竟和windows有所差別，不過不影響。在windows上需要修改環境變量和分隔符

cmd>  javah -jni -classpath %ANDROID_HOME%\platforms\android-28\android.jar;. com.penny.demo.MediaEntry