android - 使用 onTouchEvent Android 旋转、缩放/缩放、拖动位图

Question

我希望能够用手指旋转和缩放/缩放我的位图，我已经为此寻找了所有示例项目，但它们都与我的代码不匹配。这是我的 onTouchListener 代码。

public class MyView extends View {
    private float mX, mY;
    private float XText, YText;
    private float Textpixel;
    private static final float TOUCH_TOLERANCE = 2;

    //image
    float xImage = 200;
    float yImage = 200;

    public MyView(Context c) {
        super(c);
        mCanvas     = new Canvas();
        mPath       = new Path();
    }

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

    @Override
    protected void onDraw(Canvas canvas) {
        if ( layouttype == "small"){
            Textpixel   = 16f;
        }else if(layouttype == "normal"){
            Textpixel   = 16f;
        }else if (layouttype == "large"){
            Textpixel   = 18f;
        }else {
            Textpixel   = 20f;
        }

        if(bmImgAttach != null) {
            canvas.drawBitmap(bmImgAttach, xImage, yImage, null);
        }
    }

    public void touch_start(float x, float y, MotionEvent event) {
        if (isImage) {
            if(isTouchImage) {
                xImage = event.getX();
                yImage = event.getY();
            }
        }
    }

    private void touch_move(float x, float y, MotionEvent event) {
        if(isImage) {
            if(isTouchImage) {
                xImage = event.getX();
                yImage = event.getY();
            }
        }
    }

    private void touch_up(float x, float y, MotionEvent event) {
        if(isImage) {
            if(isTouchImage) {
                xImage = event.getX();
                yImage = event.getY();
            }
        }
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        final float x = event.getX();
        final float y = event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(x, y, event);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(x, y, event);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up(x, y, event);
                invalidate();
                break;
        }return true;
    }
}

我为每个事件创建了不同的方法，例如:

• ACTION_DOWN 事件的 touch_start 方法
• ACTION_MOVE 事件的 touch_move 方法
• ACTION_UP 事件的 touch_up 方法

Answer 1

Android 中的 Matrix 类使用 3×3 矩阵来实现所有的 2D 变换。

这是 Android 多点触控功能的快速实现 - 一根手指移动，两根手指缩放，三根手指旋转图像。

public class MultiTouch extends Activity implements OnTouchListener {

// these matrices will be used to move and zoom image
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
// we can be in one of these 3 states

private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;

// remember some things for zooming

private PointF start = new PointF(); 
private PointF mid = new PointF();
private float oldDist = 1f;
private float d = 0f;
private float newRot = 0f;
private float[] lastEvent = null;

@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ImageView view = (ImageView) findViewById(R.id.imageView);
view.setOnTouchListener(this);

}

public boolean onTouch(View v, MotionEvent event) {

// handle touch events here
ImageView view = (ImageView) v;
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
lastEvent = null;
break;

case MotionEvent.ACTION_POINTER_DOWN:

oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}

lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
d = rotation(event);
break;

case MotionEvent.ACTION_UP:

case MotionEvent.ACTION_POINTER_UP:

mode = NONE;
lastEvent = null;
break;

case MotionEvent.ACTION_MOVE:

if (mode == DRAG) {

matrix.set(savedMatrix);
float dx = event.getX() - start.x;
float dy = event.getY() - start.y;
matrix.postTranslate(dx, dy);

} else if (mode == ZOOM) {
float newDist = spacing(event);

if (newDist > 10f) {

matrix.set(savedMatrix);
float scale = (newDist / oldDist);
matrix.postScale(scale, scale, mid.x, mid.y);

}

if (lastEvent != null && event.getPointerCount() == 3) {

newRot = rotation(event);
float r = newRot - d;
float[] values = new float[9];
matrix.getValues(values);
float tx = values[2];
float ty = values[5];
float sx = values[0];
float xc = (view.getWidth() / 2) * sx;
float yc = (view.getHeight() / 2) * sx;
matrix.postRotate(r, tx + xc, ty + yc);

}
}
break;
}
view.setImageMatrix(matrix);
return true;
}
 /**

* Determine the space between the first two fingers

*/

private float spacing(MotionEvent event) {

float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);

}

/**

* Calculate the mid point of the first two fingers

*/

private void midPoint(PointF point, MotionEvent event) {

float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}
/**

* Calculate the degree to be rotated by.

* @param event

* @return Degrees

*/

private float rotation(MotionEvent event) {

double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);

}

}

然后，像这样对 ImageView 使用 scaleType=matrix

<ImageView
    android:id="@+id/imageView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scaleType="matrix"
    android:src="@drawable/app_icon" />