android113 自定义进度条

MainActivity：

package com.itheima.monitor;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.widget.ProgressBar;

public class MainActivity extends Activity {

    private MyProgressBar pb;

    static{

        System.loadLibrary("hello");

    }

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        pb = (MyProgressBar) findViewById(R.id.pb);//自定义进度条

        pb.setMax(100);

    }

   public void start(View v){

       new Thread(){

           public void run() {

               startMonitor();

           };

       }.start();

   }

   public void stop(View v){

       stopMonitor();

   }

   public native void startMonitor();

   public native void stopMonitor();

   public void show(int pressure){

       pb.setPressure(pressure);

   }

}

MyProgressBar。java

package com.itheima.monitor;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.util.AttributeSet;

import android.view.View;

/*界面：

<com.itheima.monitor.MyProgressBar

android:id="@+id/pb"

android:layout_height="wrap_content"

android:layout_width="wrap_content"

/>*/

public class MyProgressBar extends View {

    private int pressure;

    private int max;

    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.pressure = pressure;

        //使当前组件MyProgressBar视图无效，如果当前视图是可见的，那么onDraw会调用，只能在主线程使用

//        invalidate();  主线程调用这个方法

        postInvalidate();//子线城用这个方法，这样进度条才会一直绘制进度条。

    }

    public void setMax(int max) {

        this.max = max;

    }

    //在自定义组件绘制内容

    @Override

    protected void onDraw(Canvas canvas) {

        //任何组件在显示在页面上的时候onDraw方法都会调用一次，

        Paint paint = new Paint();//画笔

        if(pressure < 50){

            paint.setColor(Color.GREEN);

        }

        else if(pressure < 80){

            paint.setColor(0xffff8800);

        }

        else {

            paint.setColor(Color.RED);

        }

        canvas.drawRect(10, 10 + max - pressure, 30, 10 + max, paint);//画矩形,也就是画进度条。

        canvas.drawText("dddd", 10, 10, paint);//写文字

    }

}

hello.c

#include <jni.h>

#include <stdio.h>

#include <stdlib.h>

int getPressure(){

    //……监测电压……运算得到压力值

    return rand() % ;

}

int monitor;

JNIEXPORT void JNICALL Java_com_itheima_monitor_MainActivity_startMonitor

  (JNIEnv * env, jobject obj){//obj是MainActivity，

    monitor = ;

    while(monitor){

        //获取锅炉压力

        int pressure = getPressure();

//C中通过反射调用java的方法

        //jclass  (*FindClass)(JNIEnv*, const char*);

        jclass clazz = (*env)->FindClass(env, "com/itheima/monitor/MainActivity");

        //jmethodID  (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);

        jmethodID methodId = (*env)->GetMethodID(env, clazz, "show", "(I)V");//(I)V是方法的签名，返回值是void参数是int

        //void  (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);

        (*env)->CallVoidMethod(env, obj, methodId, pressure);//调用java的show方法

        sleep();

    }

}

JNIEXPORT void JNICALL Java_com_itheima_monitor_MainActivity_stopMonitor

 (JNIEnv * env, jobject obj){

    monitor = ;

}

//进入工程的bin\classes目录，执行javap -s Mainactivity的全包名类名，就可以查看MainActivity的所有方法的签名。