NDK之动态注册

妖狐艹你老母 2023-10-13 21:01 31阅读 0赞

jisuanqi.c

#include <jni.h>nativeMethon
    
    //实现java层被native修饰的方法
    jfloat addc(JNIEnv* env,jobject obj ,jfloat a,jfloat b){
       return a+b;
    }
    
    jfloat subc(JNIEnv* env,jobject obj ,jfloat a,jfloat b){
       return a-b;
    }
    
    jfloat mulc(JNIEnv* env,jobject obj ,jfloat a,jfloat b){
       return a*b;
    }
    
    jfloat divc(JNIEnv* env,jobject obj ,jfloat a,jfloat b){
       return a/b;
    }
    
    //绑定java方法和C方法的关系
    JNINativeMethod nativeMethon[]={
    
          {"add","(FF)F", (void*)addc},
          {"sub","(FF)F", (void*)subc},
          {"mul","(FF)F", (void*)mulc},
          {"div","(FF)F", (void*)divc}
    };
    
    //注册相应的类以及方法；
    jint registerNatives(JNIEnv* env){
    
       jclass   _jclass = (*env)->FindClass(env, "com/bree/jisuanqi/MainActivity");
    
       //RegisterNatives,注册方法；
       //第一个、第二个：env，clazz;第三个：定义的数组名；第四个：数组元素的个数
    
        if((*env)->RegisterNatives(env, _jclass, nativeMethon,sizeof(nativeMethon)/sizeof(nativeMethon[0]))!=JNI_OK)
        {
           return JNI_ERR;
        }
       return JNI_OK;
    }
    
    //动态注册
    JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved){
       JNIEnv* env;
    
    
        if( (*vm)->GetEnv(vm, (void**)&env, JNI_VERSION_1_4)!=JNI_OK){
           return JNI_ERR;
        }
    
       if(registerNatives(env)!=JNI_OK){
           return JNI_ERR;
       }
    
       return JNI_VERSION_1_4;    //必须返回这个值
    
    }

MainActivity.java

package com.bree.jisuanqi;
    
    import android.os.Bundle;
    
    import com.google.android.material.floatingactionbutton.FloatingActionButton;
    import com.google.android.material.snackbar.Snackbar;
    
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.appcompat.widget.Toolbar;
    
    import android.view.View;
    
    import android.view.Menu;
    import android.view.MenuItem;
    import android.widget.Toast;
    
    public class MainActivity extends AppCompatActivity {
    
        static{
            System.loadLibrary("jisuanqi");
        }
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            float three = add(10,20);
            Toast.makeText(this,three+"",Toast.LENGTH_SHORT).show();
    
    
            Toolbar toolbar = findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);
    
            FloatingActionButton fab = findViewById(R.id.fab);
            fab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                            .setAction("Action", null).show();
                }
            });
        }
    
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_main, menu);
            return true;
        }
    
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
    
            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings) {
                return true;
            }
    
            return super.onOptionsItemSelected(item);
        }
    
        public native float add(float one,float two);
        public native float sub(float one,float two);
        public native float mul(float one,float two);
        public native float div(float one,float two);
    }

如有问题，请私信。

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