Android 自定义View之使用传感器实现指南针效果

传感器详解：

Android Manager之SensorManager(传感器)—方向传感器(Orientation sensor)

效果图

2.核心代码

2.1.检测传感器

2.2.绘制文字

private void drawText() {
        if (val <= 15 || val >= 345) {
            text = "北";
        } else if (val > 15 && val <= 75) {
            text = "东北";
        } else if (val > 75 && val <= 105) {
            text = "东";
        } else if (val > 105 && val <= 165) {
            text = "东南";
        } else if (val > 165 && val <= 195) {
            text = "南";
        } else if (val > 195 && val <= 255) {
            text = "西南";
        } else if (val > 255 && val <= 285) {
            text = "西";
        } else if (val > 285 && val < 345) {
            text = "西北";
        }


        mTextPaint.getTextBounds(text, 0, text.length(), mTextRect);
        //文字宽度
        int mTextWidth = mTextRect.width();
        //让文字水平居中显示
        mCanvas.drawText(text, width / 2 - mTextWidth / 2, mTextHeight / 2, mTextPaint);


}

2.3.圆心数字

 private void drawCenterText() {
        String centerText = String.valueOf((int) val + "°");
        mCenterPaint.getTextBounds(centerText, 0, centerText.length(), mCenterTextRect);
        int centerTextWidth = mCenterTextRect.width();
        int centerTextHeight = mCenterTextRect.height();
        mCanvas.drawText(centerText, width / 2 - centerTextWidth / 2, mTextHeight + mOutSideRadius + centerTextHeight / 5, mCenterPaint);


}

2.4.camera相关设置

private void set3DMetrix() {
        mCameraMatrix.reset();
        mCamera.save();
        mCamera.rotateX(mCameraRotateX);
        mCamera.rotateY(mCameraRotateY);
        mCamera.getMatrix(mCameraMatrix);
        mCamera.restore();
        //camera默认旋转是View左上角为旋转中心
        //所以动作之前要，设置矩阵位置 -mTextHeight-mOutSideRadius
        mCameraMatrix.preTranslate(-getWidth() / 2, -getHeight() / 2);
        //动作之后恢复位置
        mCameraMatrix.postTranslate(getWidth() / 2, getHeight() / 2);
        mCanvas.concat(mCameraMatrix);
}

代码下载：https://download.csdn.net/download/weixin_37730482/10462764

参考：https://www.jianshu.com/p/cee9b7c3abe8?utm_source=oschina-app