指南针SurfaceView

本文介绍了一种自定义Android View实现动态旋转罗盘的方法。该View通过SurfaceView实现实时绘制,利用Canvas旋转和绘制文字等功能显示方向,并通过线程循环更新画布,实现了指南针的效果。

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自定义View

public class MyView extends SurfaceView {
    private float degree;

    public float getDegree() {
        return degree;
    }

    public void setDegree(float degree) {
        this.degree = degree;
    }

    private SurfaceHolder.Callback callback;
    private int width;
    private int height;
    private Paint mPaint;
    private Paint mPaintText;
    private String[] dicression={"南","东","北","西"};
    public MyView(Context context) {
        super(context);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint=new Paint();
        mPaint.setStrokeWidth(5);
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.STROKE);

        mPaintText=new Paint();
        mPaintText.setTextSize(20);
        mPaintText.setTextAlign(Paint.Align.CENTER);
        mPaintText.setColor(Color.BLUE);
        final SurfaceHolder holder=getHolder();
        callback= new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {

               // surfaceHolder.lockCanvas(new Rect());
                new  Thread(new Runnable() {
                    @Override
                    public void run() {
                        while (true){
                            Canvas canvas=holder.lockCanvas();

                            canvas.drawColor(Color.WHITE);

                            canvas.drawCircle(width/2,height/2,200,mPaint);
                            canvas.drawCircle(width / 2, height / 2, 8, mPaint);
                            canvas.rotate(degree,width/2,height/2);
                            canvas.save();
                            for (int i=0;i<4;i++){
                                canvas.rotate(360/4f*i,width/2,height/2);
                                canvas.drawLine(width/2,height/2-200,width/2,height/2-170,mPaint);
                                canvas.drawText(dicression[i],width/2,height/2+220,mPaintText);

                            }
                            canvas.drawLine(width/2,height/2,width/2,height/2-150,mPaint);
                            canvas.restore();
                           // canvas.drawBitmap(mBitmap,0,0,null);

                            holder.unlockCanvasAndPost(canvas);

                        }
                    }
                }).start();
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {

            }
        };
        holder.addCallback(callback);
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width=getDefaultSize(getSuggestedMinimumWidth(),widthMeasureSpec);
        height=getDefaultSize(getSuggestedMinimumHeight(),heightMeasureSpec);
        setMeasuredDimension(width,height);
        mBitmap=Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_8888);
    }
}

MainActivity

public class MyView extends SurfaceView {
    private float degree;

    public float getDegree() {
        return degree;
    }

    public void setDegree(float degree) {
        this.degree = degree;
    }

    private SurfaceHolder.Callback callback;
    private int width;
    private int height;
    private Paint mPaint;
    private Paint mPaintText;
    private String[] dicression={"南","东","北","西"};
    public MyView(Context context) {
        super(context);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint=new Paint();
        mPaint.setStrokeWidth(5);
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.STROKE);

        mPaintText=new Paint();
        mPaintText.setTextSize(20);
        mPaintText.setTextAlign(Paint.Align.CENTER);
        mPaintText.setColor(Color.BLUE);
        final SurfaceHolder holder=getHolder();
        callback= new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {

               // surfaceHolder.lockCanvas(new Rect());
                new  Thread(new Runnable() {
                    @Override
                    public void run() {
                        while (true){
                            Canvas canvas=holder.lockCanvas();

                            canvas.drawColor(Color.WHITE);

                            canvas.drawCircle(width/2,height/2,200,mPaint);
                            canvas.drawCircle(width / 2, height / 2, 8, mPaint);
                            canvas.rotate(degree,width/2,height/2);
                            canvas.save();
                            for (int i=0;i<4;i++){
                                canvas.rotate(360/4f*i,width/2,height/2);
                                canvas.drawLine(width/2,height/2-200,width/2,height/2-170,mPaint);
                                canvas.drawText(dicression[i],width/2,height/2+220,mPaintText);

                            }
                            canvas.drawLine(width/2,height/2,width/2,height/2-150,mPaint);
                            canvas.restore();
                           // canvas.drawBitmap(mBitmap,0,0,null);

                            holder.unlockCanvasAndPost(canvas);

                        }
                    }
                }).start();
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {

            }
        };
        holder.addCallback(callback);
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width=getDefaultSize(getSuggestedMinimumWidth(),widthMeasureSpec);
        height=getDefaultSize(getSuggestedMinimumHeight(),heightMeasureSpec);
        setMeasuredDimension(width,height);
        mBitmap=Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_8888);
    }
}
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