Question

我可以用手指在画布上绘画，但是我不能用两根手指来缩放它而不会丢失缩放比例

我想做无限的画布尺寸

我有这段代码：

public class MainActivity1 extends AppCompatActivity {

DrawingView dv ;
private Paint mPaint;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    dv = new DrawingView(this);
    setContentView(dv);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.GREEN);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(12);
}

public class DrawingView extends View {

    public int width;
    public  int height;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Path    mPath;
    private Paint   mBitmapPaint;
    Context context;
    private Paint circlePaint;
    private Path circlePath;

    public DrawingView(Context c) {
        super(c);
        context=c;
        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        circlePaint = new Paint();
        circlePath = new Path();
        circlePaint.setAntiAlias(true);
        circlePaint.setColor(Color.BLUE);
        circlePaint.setStyle(Paint.Style.STROKE);
        circlePaint.setStrokeJoin(Paint.Join.MITER);
        circlePaint.setStrokeWidth(4f);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        mBitmap = Bitmap.createBitmap(1000, 1000, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.drawBitmap( mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath( mPath,  mPaint);
        canvas.drawPath( circlePath,  circlePaint);
    }

    private float mX, mY;
    private static final float TOUCH_TOLERANCE = 4;

    private void touch_start(float x, float y) {
        mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
    }

    private void touch_move(float x, float y) {
        float dx = Math.abs(x - mX);
        float dy = Math.abs(y - mY);
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
            mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
            mX = x;
            mY = y;

            circlePath.reset();
            circlePath.addCircle(mX, mY, 30, Path.Direction.CW);
        }
    }

    private void touch_up() {
        mPath.lineTo(mX, mY);
        circlePath.reset();
        // commit the path to our offscreen
        mCanvas.drawPath(mPath,  mPaint);
        // kill this so we don't double draw
        mPath.reset();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();



        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up();
                invalidate();
                break;
        }
        return true;
    }
}


}

请告诉我如何做到这一点？

而且我也想做无限的画布尺寸 - 它是可选的。主要问题是缩放

Answer 1

我的建议 - 你可以使用opengl。看起来你想要创建一些抽屉，但帆布不是完美的解决方案。目前几乎所有设备都支持opengl es。它比画布更快，你可以更容易地制作许多其他功能（如缩放，图像粘贴，3d对象等）。 Here你可以找到一个很好的教程。

Answer 2

Yoo应该使用ScaleGestureDetector来缩放画布。这是我的示例代码：

     private class MyScaleGestureListener implements ScaleGestureDetector.OnScaleGestureListener { 
           public boolean onScale(ScaleGestureDetector detector) {
              scaleFactor *= detector.getScaleFactor(); 
              return true;
        }
           public boolean onScaleBegin(ScaleGestureDetector detector) { 
              Log.d("myZoomTag", "SCALE STARTED"); 
              return true; 
        }
           public void onScaleEnd(ScaleGestureDetector detector) { 
             Log.d("myZoomTag", "SCALE ENDED"); 
        } 

  }

这里scaleFactor是全局变量。在onDraw方法中，您应该执行以下操作：

bitmapWidth *= scaleFactor;
bitmapHeight *= scaleFactor;

如何用两个手指缩放画布并移动？

2 个答案: