Android使用Jni实现压力锅数据检测效果示例

package com.android.imooc.jni;
import com.android.imooc.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
/**
 * @描述     模仿压力锅检测数据
 * @项目名称   App_imooc
 * @包名     com.android.imooc.jni
 * @类名     MonitorActivity
 * @author   chenlin
 * @date    2012年6月9日 下午3:18:11
 * @version   1.0
 */
public class MonitorActivity extends Activity {
  static{
    System.loadLibrary("monitor");
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_monitor);
  }
  public void start(View view){
    startMonitor();
  }
  public void stop(View view){
    stopMonitor();
  }
  public native void startMonitor();
  public native void stopMonitor();
}

#include 
#include 
#include 
#include 
//获得0到100的随机数
int getPressure(){
  return rand() % 101;
}

package com.android.imooc.jni;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
public class MyProgressBar extends View {
  //压力
  private int mPresure;
  //最大值
  private int mMax;
  public MyProgressBar(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }
  public MyProgressBar(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public MyProgressBar(Context context) {
    super(context);
  }
  public void setPressure(int pressure) {
    this.mPresure = pressure;
    // invalidate();
    postInvalidate();
  }
  public void setMax(int max) {
    this.mMax = max;
  }
  @Override
  protected void onDraw(Canvas canvas) {
    Paint paint = new Paint();
    if (mPresure <50) {
      paint.setColor(Color.GREEN);
    } else if (mPresure <80) {
      paint.setColor(0xffff8800);
    } else {
      paint.setColor(Color.RED);
    }
    canvas.drawRect(10, 10 + mMax - mPresure, 30, 10 + mMax, paint);
  }
}

javah com.android.imooc.jni.MonitorActivity

/*
 * Class:   com_android_imooc_jni_MonitorActivity
 * Method:  startMonitor
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_android_imooc_jni_MonitorActivity_startMonitor
 (JNIEnv *, jobject);
/*
 * Class:   com_android_imooc_jni_MonitorActivity
 * Method:  stopMonitor
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_android_imooc_jni_MonitorActivity_stopMonitor
 (JNIEnv *, jobject);

private MyProgressBar mProgressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_monitor);
  mProgressBar = (MyProgressBar) findViewById(R.id.pb);
  mProgressBar.setMax(100);
}
public void showProgress(int progress){
  mProgressBar.setPressure(progress);
}

JNIEXPORT void JNICALL Java_com_android_imooc_jni_MonitorActivity_startMonitor
(JNIEnv * env , jobject obj){
while(1){
  //得到压力数据
   int progress = getPressure();
   //使用反射的方法调用java里的showProgress方法
   //1、拿到字节吗
   jclass clazz = ( *env)->FindClass(env, "com/android/imooc/jni/MonitorActivity");
   //2、获得方法id，首先要获得函数签名，进入到项目的bin/classes目录-->打开cmd窗口-->输入命令
  // E:\androidproject\App_imooc\bin\classes>javap -s com/android/imooc/jni/MonitorActivity
  //获得签名“(I)V”
    jmethodID id = ( *env)->GetMethodID(env, clazz, "showProgress", "(I)V");
   //3、回调
  ( *env)->CallVoidMethod(env, obj, id, progress);
}
}

public void start(View view){
    new Thread(new Runnable() {
      @Override
      public void run() {
        startMonitor();
      }
    }).start();
}

while(monitor){
…………………
}

#include 
#include 
#include 
#include 
//获得0到100的随机数
int getPressure(){
  return rand() % 101;
}
int monitor;
JNIEXPORT void JNICALL Java_com_android_imooc_jni_MonitorActivity_startMonitor
(JNIEnv * env , jobject obj){
  mOnitor= 1;
  while(monitor){
    int progress = getPressure();
       //使用反射调用java方法
       //拿到字节吗
      jclass clazz = ( *env)->FindClass(env, "com/android/imooc/jni/MonitorActivity");
      //获得方法id
      //jmethodID  (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
      jmethodID id = ( *env)->GetMethodID(env, clazz, "showProgress", "(I)V");
      //回调
      //void    (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);
      ( *env)->CallVoidMethod(env, obj, id, progress);
      sleep(0.3f);
  }
}
JNIEXPORT void JNICALL Java_com_android_imooc_jni_MonitorActivity_stopMonitor
(JNIEnv * env , jobject obj){
  mOnitor= 0;
}

/**
 * @描述     模仿压力锅检测数据
 * @项目名称   App_imooc
 * @包名     com.android.imooc.jni
 * @类名     MonitorActivity
 * @author   chenlin
 * @date    2012年6月9日 下午3:18:11
 * @version   1.0
 */
public class MonitorActivity extends Activity {
  private MyProgressBar mProgressBar;
  static{
    System.loadLibrary("monitor");
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_monitor);
    mProgressBar = (MyProgressBar) findViewById(R.id.pb);
    mProgressBar.setMax(100);
  }
  public void start(View view){
    new Thread(new Runnable() {
      @Override
      public void run() {
        startMonitor();
      }
    }).start();
  }
  public void stop(View view){
    stopMonitor();
  }
  public native void startMonitor();
  public native void stopMonitor();
  public void showProgress(int progress){
    mProgressBar.setPressure(progress);
  }
}