Android缩放图像视图与ViewPager冲突的滑动手势
创始人
2024-08-21 14:00:22
0

要解决Android缩放图像视图(ImageView)与ViewPager冲突的滑动手势问题,可以通过自定义一个可缩放的ImageView,然后在ViewPager中使用这个自定义的ImageView来代替原生的ImageView。

以下是一个示例代码,展示了如何实现这个自定义的可缩放的ImageView:

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;

public class ZoomableImageView extends AppCompatImageView {
    private Matrix matrix;
    private float[] matrixValues;

    private PointF startPoint;
    private float startDistance;
    private float startScale;
    private float maxScale;

    private ScaleGestureDetector scaleGestureDetector;
    private GestureDetector gestureDetector;

    public ZoomableImageView(Context context) {
        super(context);
        init();
    }

    public ZoomableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public ZoomableImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        matrix = new Matrix();
        matrixValues = new float[9];
        startPoint = new PointF();

        scaleGestureDetector = new ScaleGestureDetector(getContext(), new ScaleGestureListener());
        gestureDetector = new GestureDetector(getContext(), new DoubleTapGestureListener());

        setScaleType(ScaleType.MATRIX);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        scaleGestureDetector.onTouchEvent(event);
        gestureDetector.onTouchEvent(event);

        switch (event.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                startPoint.set(event.getX(), event.getY());
                break;
            case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount() == 1) {
                    float dx = event.getX() - startPoint.x;
                    float dy = event.getY() - startPoint.y;
                    startPoint.set(event.getX(), event.getY());

                    matrix.postTranslate(dx, dy);
                    setImageMatrix(matrix);
                }
                break;
        }

        return true;
    }

    private class ScaleGestureListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            float scaleFactor = detector.getScaleFactor();
            float focusX = detector.getFocusX();
            float focusY = detector.getFocusY();

            matrix.getValues(matrixValues);
            float currentScale = matrixValues[Matrix.MSCALE_X];

            float newScale = currentScale * scaleFactor;
            if (newScale < startScale) {
                newScale = startScale;
            } else if (newScale > maxScale) {
                newScale = maxScale;
            }

            float scaleRatio = newScale / currentScale;
            matrix.postScale(scaleRatio, scaleRatio, focusX, focusY);
            setImageMatrix(matrix);

            return true;
        }

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            matrix.getValues(matrixValues);
            startScale = matrixValues[Matrix.MSCALE_X];
            maxScale = startScale * 3; // 设置最大缩放比例为初始缩放比例的3倍

            return true;
        }
    }

    private class DoubleTapGestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            matrix.getValues(matrixValues);
            float currentScale = matrixValues[Matrix.MSCALE_X];

            float targetScale;
            if (currentScale < maxScale) {
                targetScale = maxScale;
            } else {
                targetScale = startScale;
            }

            float scaleRatio = targetScale / currentScale;
            matrix.postScale(scaleRatio, scaleRatio, e.getX(), e.getY());
            setImageMatrix(matrix);

            return true;
        }
    }
}

在ViewPager布局中使用这个自定义的ImageView:



    


这样就可以在ViewPager中实现缩放图像的功能,并避免与ViewPager的滑动手势冲突。

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