Android 开发中 JAVA 调用 C＋＋
[代码] 步骤 #1:使用ANT编译项目 NativeAdd.javaview sourceprint?01 package org.apache;
02
03 import Android.util.Log;
04
05 public class NativeAdd {
06 static {
07 try {
08 Log.i("JNI", "Trying to load libNativeAdd.so");
09 System.loadLibrary("NativeAdd");
10 }
11 catch (UnsatisfiedLinkError ule) {
12 Log.e("JNI", "WARNING: Could not load libNativeAdd.so");
13 }
14 }
15
16 public static native long add(long a, long b);
17 }
[代码] 下面片断给出主activity中如何调用这个类/方法
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01 public void onClick(View view) {
02 Log.i(LOG_TAG, "onClick");
03
04 EditText a = (EditText) findViewById(R.id.a);
05 EditText b = (EditText) findViewById(R.id.b);
06 EditText c = (EditText) findViewById(R.id.c);
07 Log.i(LOG_TAG, "calling native method");
08 long sum = NativeAdd.add( Long.parseLong(a.getText().toString()),
09 Long.parseLong(b.getText().toString()));
10 Log.i(LOG_TAG, "back from native method");
11 String text = Long.toString(sum);
12 c.setText("Native add returns = " + text.subSequence(0, text.length()));
13 }
[代码] 步骤#2:运行下面的命令产生头文件
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1 javah -classpath ../../Android.jar;../bin/classes; org.apache.NativeAdd
[代码] 新产生的头文件“(org_apache_CallNative.h”内容如下
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01 /* DO NOT EDIT THIS FILE - it is machine generated */
02 #include
03 /* Header for class org_apache_NativeAdd */
04
05 #ifndef _Included_org_apache_NativeAdd
06 #define _Included_org_apache_NativeAdd
07 #ifdef __cplusplus
08 extern "C" {
09 #endif
10 /*
11* Class: org_apache_NativeAdd
12* Method: add
13* Signature: (JJ)J
14*/
15 JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add
16 (JNIEnv *, jclass, jlong, jlong);
17
18 #ifdef __cplusplus
19 }
20 #endif
21 #endif
[代码] 步骤#3: 编写C文件如下“org_apache_NativeAdd.c”
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1 #include "org_apache_NativeAdd.h"
2
3 JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add
4 (JNIEnv *env, jclass c, jlong a, jlong b)
5 {
6 return a + b;
7 }
[代码] 步骤#5: 编译和连接 org_apache_NativeAdd.c/org_apache_NativeAdd.h为一个共享库.
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1 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
2 arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o libNativeAdd.so org_apache_NativeAdd.o
[代码] 步骤 #6: 复制编译文件到模拟器中. 同时安装APK程序.
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1 adb push native/libNativeAdd.so /system/lib
2 adb install bin/CallNative.apk
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