JNI编程demo

public class ProgressBarOperation {
    static {
        System.loadLibrary("Pressure");
    }

    public native void startMonitor();

    public native void stopMonitor();
}

    //button响应事件
    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.btn_start) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    operation.startMonitor();
                }
            }).start();
        } else if (v.getId() == R.id.btn_stop) {
            operation.stopMonitor();
        }
    }

    //这个函数和下个函数是为了测试调用一般函数和静态函数的区别
    public void setPressure(int pressure) {
        Log.e("pressure", "" + pressure);
        handler.obtainMessage(0x001, pressure, 0).sendToTarget();
    }

    public static void set(int pressure) {
        Log.e("pressure", "" + pressure);
        handler.obtainMessage(0x001, pressure, 0).sendToTarget();
    }

    private static Handler handler = new Handler(){
        public void handleMessage(android.os.Message msg) {
            if(msg.what == 0x001){
                progressBar.setProgress(msg.arg1);
            }
        };
    };

    private static Context context;
    public static void init(int pressure){
        ((MainActivity) context).setPressure(pressure);
    }

//生成随机数
int getPressure() {
    return rand() % 100;
}

int flag = JNI_TRUE;

JNIEXPORT void JNICALL Java_com_example_pressuretest_ProgressBarOperation_startMonitor(
        JNIEnv *env, jobject obj) {
    while (flag) {
        sleep(1);
        //静态方法
        //jclass clazz = env->FindClass("com/example/pressuretest/MainActivity");
        //jmethodID methodId = env->GetStaticMethodID(clazz, "set", "(I)V");
        //env->CallStaticVoidMethod(clazz, methodId, getPressure());

        //非静态方法
        jclass clazz = env->FindClass("com/example/pressuretest/MainActivity");
        jmethodID methodId = env->GetStaticMethodID(clazz, "init", "(I)V");
        env->CallStaticVoidMethod(clazz, methodId, getPressure());
        //我的这种做法是将非静态方法强制转成静态方法来实现的，不科学，具体的讨论在
        //http://ask.csdn.net/questions/325670
    }
}

JNIEXPORT void JNICALL Java_com_example_pressuretest_ProgressBarOperation_stopMonitor(
        JNIEnv *env, jobject obj) {
    flag = JNI_FALSE;
}

public class Binary {
    static {
        System.loadLibrary("binary");
    }

    public static native int[] binaryImage(int[] buff, int width, int height,
            int threshold);
}

seekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                textView.setText("阈值是：" + thresHold);
                bitmap.getPixels(pix, 0, w, 0, 0, w, h);
                // binaryImage会把pix替换掉
                int[] result_pix = Binary.binaryImage(pix, w, h, thresHold);
                result.setPixels(result_pix, 0, w, 0, 0, w, h);
                imageView.setImageBitmap(result);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {
                thresHold = progress;
                textView.setText("阈值是：" + progress);
            }
        });

JNIEXPORT jintArray JNICALL Java_com_example_binaryimage_Binary_binaryImage(
        JNIEnv *env, jclass clz, jintArray buffer, jint width, jint height,
        jint threshold) {
    jint *cbuf = env->GetIntArrayElements(buffer, JNI_FALSE);
    if (cbuf == NULL) {
        return 0; /* exception occurred */
    }
    jint alpha = 0xFF << 24;
    for (jint i = 0; i < height; i++) {
        for (jint j = 0; j < width; j++) {
            // 获得像素的颜色
            jint color = cbuf[width * i + j];
            jint red = ((color & 0x00FF0000) >> 16);
            jint green = ((color & 0x0000FF00) >> 8);
            jint blue = color & 0x000000FF;
            color = (red + green + blue) / 3;
            //__android_log_print(ANDROID_LOG_ERROR, "TAG", "pix=%d", color);
            if (color <= threshold) {
                color = 0;
            } else {
                color = 255;
            }
            color = alpha | (color << 16) | (color << 8) | color;
            cbuf[width * i + j] = color;
        }
    }
    jint size = width * height;
    jintArray result = env->NewIntArray(size);
    env->SetIntArrayRegion(result, 0, size, cbuf);
    env->ReleaseIntArrayElements(buffer, cbuf, 0);
    return result;
}