[jni] [android] 用C++开发安卓程序 |
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[jni] [android] 用C++开发安卓程序
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原理
原理其实很简单 首先用FindClass()查找java类，然后用GetMethodID()得到构造函数 构造函数的函数名是“< init >”，返回类型为"V"（void） 最后直接用NewObject()创建一个按钮 回调部分受到了别人文章和快写代码的启发，把回调类的地址传递到java中，java类接收到事件后用地址作为参数调用本地方法，本地方法把地址转换为c++回调类，调用方法 代码MainActivity.java package com.Diamond.ndk; import android.app.Activity; import android.os.Bundle; import android.widget.LinearLayout; import android.content.Context; import android.widget.Button; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Context context = MainActivity.this; LinearLayout mainLayout = new LinearLayout(this); mainLayout.setOrientation(1); setContentView(mainLayout); onCreate(context,mainLayout); } @Override protected void onDestroy() { onActivityDestroy(); super.onDestroy(); } public native void onActivityDestroy(); public native void onCreate(Context context,LinearLayout mainLayout); static { System.loadLibrary("jni"); } }MyOnClickListener.java package com.Diamond.ndk; import android.view.View; import android.util.Log; public class MyOnClickListener implements View.OnClickListener { public int address; public MyOnClickListener(int ar) { address = ar; } @Override public void onClick(View p1) { callOnClick(address); Log.d("address","" + address); } public native void callOnClick(long address); static { System.loadLibrary("jni"); } }main.cpp #include #include #include using namespace std; extern "C" { class OnClickListener { public: virtual void onClick() = 0; }; JNIEnv *Env = NULL; jobject button = NULL; const string linearlayout_package = "android/widget/LinearLayout"; const string context_package = "android/content/Context"; const string button_package = "android/widget/Button"; const string view_package = "android/view/View"; const string charsequence_package = "java/lang/CharSequence"; const string myonclicklistener_package = "com/Diamond/ndk/MyOnClickListener"; const string onclicklistener_package = "android/view/View$OnClickListener"; jclass LinearLayout = NULL; jclass Context = NULL; jclass Button = NULL; jclass View = NULL; jclass MyOnClickListener = NULL; jmethodID init_button = NULL; jmethodID init_myonclicklistener = NULL; jmethodID addView_linearlayout = NULL; jmethodID setText_button = NULL; jclass getClass(string package); void setText(jobject button, string text); class MyListener : public OnClickListener { public: virtual void onClick() { //用了会崩溃，不知道为什么 //setText(button, "be clicked"); __android_log_print(ANDROID_LOG_INFO, "test", "test"); } }; MyListener *listener = NULL; JNIEXPORT void JNICALL Java_com_Diamond_ndk_MainActivity_onCreate(JNIEnv * env, jobject thiz, jobject context, jobject mainLayout) { Env = env; LinearLayout = getClass(linearlayout_package); Context = getClass(context_package); Button = getClass(button_package); View = getClass(view_package); MyOnClickListener = getClass(myonclicklistener_package); setText_button = Env->GetMethodID(Button, "setText", ("(L" + charsequence_package + ";)V").data()); init_button = env->GetMethodID(Button, "", ("(L" + context_package + ";)V").data()); button = env->NewObject(Button, init_button, context); setText(button, "JNI Button"); listener = new MyListener(); jmethodID setOnClickListener_button = env->GetMethodID(Button, "setOnClickListener", ("(L" + onclicklistener_package + ";)V").data()); init_myonclicklistener = env->GetMethodID(MyOnClickListener, "", "(I)V"); jobject myonclicklistener = env->NewObject(MyOnClickListener, init_myonclicklistener, jint(listener)); env->CallVoidMethod(button, setOnClickListener_button, myonclicklistener); addView_linearlayout = env->GetMethodID(LinearLayout, "addView", ("(L" + view_package + ";)V").data()); env->CallVoidMethod(mainLayout, addView_linearlayout, button); } JNIEXPORT void JNICALL Java_com_Diamond_ndk_MainActivity_onActivityDestroy(JNIEnv * env, jobject thiz) { delete listener; } JNIEXPORT void JNICALL Java_com_Diamond_ndk_MyOnClickListener_callOnClick(JNIEnv * env, jobject thiz, jint address) { OnClickListener *listener = (OnClickListener *) address; listener->onClick(); } jclass getClass(string package) { return Env->FindClass(package.data()); } void setText(jobject button, string text) { Env->CallVoidMethod(button, setText_button, Env->NewStringUTF(text.data())); } } 效果图
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