javap -s 查看java方法签名

   工程先用eclipse生成class目录，转到class目录下执行: javap -s com.example.hellojni.MainActivity

Compiled from "MainActivity.java"
public class com.example.hellojni.MainActivity extends android.app.Activity {
  static {};
    Signature: ()V

  public com.example.hellojni.MainActivity();
    Signature: ()V

  protected void onCreate(android.os.Bundle);
    Signature: (Landroid/os/Bundle;)V

  public boolean onCreateOptionsMenu(android.view.Menu);
    Signature: (Landroid/view/Menu;)Z

  public native java.lang.String stringFromJNI(); //native 方法
    Signature: ()Ljava/lang/String;  //签名

  public native int max(int, int); //native 方法
    Signature: (II)I    //签名
}

最后附上com/example/hellojni/MainActivity.java代码:

package com.example.hellojni;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView  tv = new TextView(this);
        tv.setText( stringFromJNI() );
        setContentView(tv);        
        Log.d("JNI", "max = " + max(10, 100));
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    
    public native String  stringFromJNI();
    public native int max(int a,int b); 
    static {
        System.loadLibrary("hellojni");
    }
}