在Android中缩小缩放布局

Question

这是我的代码，用于执行缩放操作。只有当我在没有任何在ClickListner上实现的小部件的布局中使用它时，它才有效。如果我把手指放在这些小部件上，我不知道如何放大我的布局。

package com.example.cosmin.catanadvice;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.FrameLayout;
/**
 * Layout that provides pinch-zooming of content. This view should have exactly     one child
 * view containing the content.
 */
public class ZoomLayout extends FrameLayout implements ScaleGestureDetector.OnScaleGestureListener {
private enum Mode {
    NONE,
    DRAG,
    ZOOM
}
private static final String TAG = "ZoomLayout";
private static final float MIN_ZOOM = 1.0f;
private static final float MAX_ZOOM = 4.0f;
private Mode mode = Mode.NONE;
private float scale = 1.0f;
private float lastScaleFactor = 0f;
// Where the finger first  touches the screen
private float startX = 0f;
private float startY = 0f;
// How much to translate the canvas
private float dx = 0f;
private float dy = 0f;
private float prevDx = 0f;
private float prevDy = 0f;
public ZoomLayout(Context context) {
    super(context);
    init(context);
}
public ZoomLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}
public ZoomLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init(context);
}
private void init(Context context) {
    final ScaleGestureDetector scaleDetector = new ScaleGestureDetector(context, this);
    this.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent motionEvent) {
            switch (motionEvent.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    Log.i(TAG, "DOWN");
                    if (scale > MIN_ZOOM) {
                        mode = Mode.DRAG;
                        startX = motionEvent.getX() - prevDx;
                        startY = motionEvent.getY() - prevDy;
                    }
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (mode == Mode.DRAG) {
                        dx = motionEvent.getX() - startX;
                        dy = motionEvent.getY() - startY;
                    }
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    mode = Mode.ZOOM;
                    break;
                case MotionEvent.ACTION_POINTER_UP:
                    mode = Mode.DRAG;
                    break;
                case MotionEvent.ACTION_UP:
                    Log.i(TAG, "UP");
                    mode = Mode.NONE;
                    prevDx = dx;
                    prevDy = dy;
                    break;
            }
            scaleDetector.onTouchEvent(motionEvent);
            if ((mode == Mode.DRAG && scale >= MIN_ZOOM) || mode == Mode.ZOOM) {
                getParent().requestDisallowInterceptTouchEvent(true);
                float maxDx = (child().getWidth() - (child().getWidth() / scale)) / 2 * scale;
                float maxDy = (child().getHeight() - (child().getHeight() / scale))/ 2 * scale;
                dx = Math.min(Math.max(dx, -maxDx), maxDx);
                dy = Math.min(Math.max(dy, -maxDy), maxDy);
                Log.i(TAG, "Width: " + child().getWidth() + ", scale " + scale + ", dx " + dx
                        + ", max " + maxDx);
                applyScaleAndTranslation();
            }
            return true;
        }
    });
}
// ScaleGestureDetector
@Override
public boolean onScaleBegin(ScaleGestureDetector scaleDetector) {
    Log.i(TAG, "onScaleBegin");
    return true;
}
@Override
public boolean onScale(ScaleGestureDetector scaleDetector) {
    float scaleFactor = scaleDetector.getScaleFactor();
    Log.i(TAG, "onScale" + scaleFactor);
    if (lastScaleFactor == 0 || (Math.signum(scaleFactor) == Math.signum(lastScaleFactor))) {
        scale *= scaleFactor;
        scale = Math.max(MIN_ZOOM, Math.min(scale, MAX_ZOOM));
        lastScaleFactor = scaleFactor;
    } else {
        lastScaleFactor = 0;
    }
    return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector scaleDetector) {
    Log.i(TAG, "onScaleEnd");
}
private void applyScaleAndTranslation() {
    child().setScaleX(scale);
    child().setScaleY(scale);
    child().setTranslationX(dx);
    child().setTranslationY(dy);
}
private View child() {
    return getChildAt(0);
}
}

Answer 1

您可以使用已经实现此功能的第三方库之一，支持各种手势：

https://github.com/chrisbanes/PhotoView