学步园

PerformanceTest.java

package com.jni;</p> <p>import android.app.Activity;<br /> import android.os.Bundle;<br /> import android.util.Log;</p> <p>public class PerformanceTest extends Activity {<br /> static<br /> {<br /> try<br /> {<br /> System.loadLibrary("PerformanceTest");<br /> } catch (UnsatisfiedLinkError ule)<br /> {<br /> System.err.println("WARNING: Could not load library!");<br /> }<br /> }<br /> private final String PerformanceTestTAG ="PerformanceTest:performanceTestFunc :";<br /> /* JNI 测试函数 */<br /> private native void emptyJniFunction();<br /> /* JAVA测试函数 */<br /> private void emptyJavaFunction()<br /> {</p> <p> }<br /> /** Called when the activity is first created. */<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> setContentView(R.layout.main);<br /> performanceTestFunc();<br /> }<br /> /* 性能测试函数 */<br /> public void performanceTestFunc()<br /> {<br /> /* 测试数量级为100万次 */<br /> int mLoopCount = 1000000;<br /> int i = 0;<br /> int base = 1000000;<br /> String timeStr_ms; /* 毫秒对应String*/<br /> /* 精确度为纳秒级 */<br /> long startTime = System.nanoTime();<br /> /* JNI 调用 */<br /> for(i = 0;i <= mLoopCount; ++ i)<br /> {<br /> emptyJniFunction();<br /> }<br /> long endTime = System.nanoTime();<br /> timeStr_ms = String.valueOf((endTime-startTime)/base);<br /> Log.v(PerformanceTestTAG+"In Jni:", timeStr_ms+"ms");<br /> startTime = System.nanoTime();<br /> /* JAVA 调用 */<br /> for(i = 0;i <= mLoopCount; ++ i)<br /> {<br /> emptyJavaFunction();<br /> }<br /> endTime = System.nanoTime();<br /> timeStr_ms = String.valueOf((endTime-startTime)/base);<br /> Log.v(PerformanceTestTAG+"In JAVA:", timeStr_ms+"ms");<br /> }<br /> }

com_jni_PerformanceTest.c

/* DO NOT EDIT THIS FILE - it is machine generated */<br /> #include <jni.h><br /> /* Header for class com_jni_PerformanceTest */</p> <p>#ifndef _Included_com_jni_PerformanceTest<br /> #define _Included_com_jni_PerformanceTest<br /> #ifdef __cplusplus<br /> extern "C" {<br /> #endif<br /> /*<br /> * Class: com_jni_PerformanceTest<br /> * Method: emptyJniFunction<br /> * Signature: ()V<br /> */<br /> JNIEXPORT void JNICALL Java_com_jni_PerformanceTest_emptyJniFunction<br /> (JNIEnv *env, jobject obj)<br /> {</p> <p>}<br /> JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved)<br /> {<br /> JNIEnv *env;<br /> int result;</p> <p> result = JNI_VERSION_1_4;<br /> return result;</p> <p>}<br /> #ifdef __cplusplus<br /> }<br /> #endif<br /> #endif<br />

Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE     := PerformanceTest

LOCAL_SRC_FILES :=  src/com_jni_PerformanceTest.c

include $(BUILD_SHARED_LIBRARY)

如上图所示，通过Jni调用c的空实现函数，调用100万次，用时41747ms，而使用java调用java的空实现函数100万次，用时25378ms。以上测试数量级为100万次，系统android 2.2,测试于android模拟器上，jdk1.6.0_17。