Android 4.0 JNI Hello World 开发图解(2)

package com.jsd.jni.demo;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;


/**
 * 
 * @author jankey
 *
 */
public class JsdJniActivity extends Activity {

private Button mJniDemo = null;
private TextView mGetJni = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        findById();
    }
    
    private void findById(){
    mJniDemo = (Button) findViewById(R.id.jniDemo);
    mGetJni = (TextView) findViewById(R.id.getJni);
    mJniDemo.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mGetJni.setText(getJniDatas());
}
});
    }
    
    /**
     * A native method that is implemented by the 
     * 'hello-jni' native library, which is packaged
     * with this application.
     * @return
     */
    public native String getJniDatas();
    
    /**
     *This is another native method declaration that is *not*
     * implemented by 'hello-jni'. This is simply to show that
     * you can declare as many native methods in your Java code
     * as you want, their implementation is searched in the
     * currently loaded native libraries only the first time
     * you call them.
     *
     * Trying to call this function will result in a
     * java.lang.UnsatisfiedLinkError exception !
     * @return
     */
    public native String unimplementedGetJniDatas();
    
    /**
     * this is used to load the 'hello-jni' library on application
     * startup. The library has already been unpacked into
     * /data/data/com.example.HelloJni/lib/libhello-jni.so at
     * installation time by the package manager.
     */
    static{
    System.loadLibrary("hello-jni");
    }   
}

上面有注释，其native方法为JNI需要调用与执行的方法，

在布局里就添加了一个按钮与一个文本，使用按钮单点后来获得文本显示的字符为JNI所得来的数据,其实这个过程很简单，基本就是NDK里面本身的列子般过来运行一样，等这都完了，先不要急于运行，你需要先把C文件进行编译后才能执行运行APP，在命令行进入其目录的JNI目录,使用ndk-build命令来构建编译：

你会看到：jankey@jankey-ThinkPad-Edge:~/workspace/jni_demo/jni$ ndk-build 
Compile thumb  : hello-jni <= hello-jni.c
SharedLibrary  : libhello-jni.so
Install        : libhello-jni.so => libs/armeabi/libhello-jni.so，生成了两个文件目录：

即两个.so为后缀的文件，在这里基本就没什么问题了，这样就建立了C与JAVA通信的一个过程，OK，使用CTRI+F11开始运行其APP：

，先我们可以单击来获取JNI返回回来的数据了:

这就把数据给调出来了，如果你是初学者，你还等什么呢，赶快动手吧，希望这能给在入门里做最给里的参考，谢谢。