Android 开发中 JAVA 调用 C++

http://www.oschina.net/code/snippet_4873_3279#4874

代码片段(7)[全屏查看所有代码]

1. [代码]步骤 #1:使用ANT编译项目 NativeAdd.java     

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

package org.apache;   import Android.util.Log;   public class NativeAdd {      static {          try {              Log.i( "JNI" , "Trying to load libNativeAdd.so" );              System.loadLibrary( "NativeAdd" );          }          catch (UnsatisfiedLinkError ule) {              Log.e( "JNI" , "WARNING: Could not load libNativeAdd.so" );          }      }        public static native long add( long a, long b); }

2. [代码]下面片断给出主activity中如何调用这个类/方法     

?

1 2 3 4 5 6 7 8 9 10 11 12 13

public void onClick(View view) {        Log.i(LOG_TAG, "onClick" );          EditText a = (EditText) findViewById(R.id.a);        EditText b = (EditText) findViewById(R.id.b);        EditText c = (EditText) findViewById(R.id.c);        Log.i(LOG_TAG, "calling native method" );        long sum = NativeAdd.add( Long.parseLong(a.getText().toString()),                Long.parseLong(b.getText().toString()));        Log.i(LOG_TAG, "back from native method" );        String text = Long.toString(sum);        c.setText( "Native add returns = " + text.subSequence( 0 , text.length()));    }

3. [代码]步骤#2:运行下面的命令产生头文件     

?

1	javah -classpath ../../Android.jar;../bin/classes; org.apache.NativeAdd

4. [代码]新产生的头文件“(org_apache_CallNative.h”内容如下     

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

/* DO NOT EDIT THIS FILE - it is machine generated */ #include /* Header for class org_apache_NativeAdd */   #ifndef _Included_org_apache_NativeAdd #define _Included_org_apache_NativeAdd #ifdef __cplusplus extern "C" { #endif /*   * Class:     org_apache_NativeAdd   * Method:    add   * Signature: (JJ)J   */ JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add    (JNIEnv *, jclass, jlong, jlong);   #ifdef __cplusplus } #endif #endif

5. [代码]步骤#3: 编写C文件如下“org_apache_NativeAdd.c”     

?

1 2 3 4 5 6 7

#include "org_apache_NativeAdd.h"   JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add    (JNIEnv *env, jclass c, jlong a, jlong b) {      return a + b; }

6. [代码]步骤#5: 编译和连接 org_apache_NativeAdd.c/org_apache_NativeAdd.h为一个共享库.     

?

1 2	arm-none-linux-gnueabi- gcc  -I /usr/lib/jvm/java-1 .5.0-sun /include -I /usr/lib/jvm/java-1 .5.0-sun /include/linux  -fpic -c org_apache_NativeAdd.c arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o libNativeAdd.so org_apache_NativeAdd.o

7. [代码]步骤 #6: 复制编译文件到模拟器中. 同时安装APK程序.     

?

1 2	adb push native /libNativeAdd .so /system/lib adb install bin /CallNative .apk