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 <stdio.h>#include <stdlib.h>#include <jni.h>#include <string.h>//获得0到100的随机数int getPressure(){  return rand() % 101;}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical"  tools:context=".MainActivity" >  <Button    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:onClick="start"    android:text="开始监测" />  <Button    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:onClick="stop"    android:text="结束监测" />  <com.android.imooc.jni.MyProgressBar    android:id="@+id/pb"    android:layout_width="wrap_content"    android:layout_height="wrap_content" /></LinearLayout>

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;@Overrideprotected 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 <stdio.h>#include <stdlib.h>#include <jni.h>#include <string.h>//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);  }}