JNI中java类型的简写

在JNI中，当我们使用GetFieldID/GetStaticFieldID或GetMethodID/GetStaticMethodID及定义JNINativeMethod等时，我们需要表示成员变量的类型，或函数传入参数或返回的类型。JNI把Field的类型，或函数传入参数或返回值的类型进行简写以 char*的形式进行表示。

<wbr><div>对于<strong>成员变量</strong>，<span style="color:#000080">直接用java类型的简写表示成员变量的类型就可以</span> </div> <div><span style="color:#0000ff">比如："I"表示该成员变量是Int类型</span></div> <div><span style="color:#0000ff">"Ljava/lang/String;"表示该成员变量是String类型</span></div> <div> <strong>示例1</strong>：</div> <div> <div> jfieldID str = (env)-&gt;GetFieldID(objectClass,"name","Ljava/lang/String;");</div> <div> jfieldID ival = (env)-&gt;GetFieldID(objectClass,"serial","I");</div> </div> <div>对于<strong>成员函数</strong>，<span style="color:#000080">是以"(*)+"形式表示函数的有哪些传入参数，传入参数的类型，返回值的类型。"()" 中的字符表示传入参数，后面的则代表返回值</span>。</div> <div>例如：</div> <div><span style="color:#0000ff">"()V" 就表示void Func();</span></div> <div><span style="color:#0000ff">"(II)V" 表示 void Func(int, int);</span></div> <div><span style="color:#0000ff">"(Ljava/lang/String;Ljava/lang/String;)I".表示 int Func(String,String)</span></div> <div><span style="font-family:Verdana,sans-serif; font-size:13px"><strong>示例2</strong>：</span></div> <div> <span style="font-family:Verdana,sans-serif"></span> <div><span style="color:#3366ff">static JNINativeMethod gPowerManagerServiceMethods[] = {</span></div> <div><span style="color:#3366ff"> /* name, signature, funcPtr */</span></div> <div><span style="color:#3366ff"> { "nativeInit", "()V",</span></div> <div><span style="color:#3366ff"> (void*) android_server_PowerManagerService_nativeInit },</span></div> <div><span style="color:#3366ff"> { "nativeSetPowerState", "(ZZ)V",</span></div> <div><span style="color:#3366ff"> (void*) android_server_PowerManagerService_nativeSetPowerState },</span></div> <div><span style="color:#3366ff"> { "nativeStartSurfaceFlingerAnimation", "(I)V",</span></div> <div><span style="color:#3366ff"> (void*) android_server_PowerManagerService_nativeStartSurfaceFlingerAnimation },</span></div> <div><span style="color:#3366ff">};</span></div> <span style="color:#000080">关于</span><strong><span style="font-size:13px">类型简写</span></strong><span style="color:#000080">，首先请参照下表。</span> </div> <div> <span style="font-family:Verdana,sans-serif; font-size:13px"><strong>表A</strong><br></span> <div><br></div> <div> <div align="center"> <table border="1" cellspacing="0" cellpadding="0" width="535"><tbody> <tr> <td valign="top"> <p><strong>Java类型</strong></p> </td> <td valign="top"> <p><strong>符号</strong></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Boolean</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">Z</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Byte</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">B</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Char</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">C</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Short</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">S</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Int</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">I</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Long</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">L</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Float</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">F</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Double</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">D</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">Void</span></p> </td> <td valign="top"> <p><span style="color:#0000ff">V</span></p> </td> </tr> <tr> <td valign="top"> <p><span style="color:#0000ff">objects对象</span></p> </td> <td valign="top"> <p><span style="font-family:宋体; font-size:13px; color:#0000ff">以"L"开头，以";"结尾，中间是用"/" 隔开的包及类名。</span></p> <p><span style="font-family:宋体; font-size:13px; color:#0000ff">比如：Ljava/lang/String;</span></p> <p><span style="font-family:宋体; font-size:13px; color:#0000ff">如果是嵌套类，则用$来表示嵌套。</span></p> <p><span style="font-family:宋体; font-size:13px; color:#0000ff">例如 "(Ljava/lang/String;Landroid/os/FileUtils$FileStatus;)Z"</span></p> </td> </tr> </tbody></table> <div> <div> <span style="color:#000080">另外数组类型的简写</span>,则用"["加上如表A所示的对应类型的简写形式进行表示就可以了，</div> <div> <strong>比如</strong><span style="color:#000080">：</span><span style="color:#ff6600">[I 表示 int []</span> </div> </div> </div> </div> </div> </wbr>