我们可以在Android中使用缩放手势检测器进行缩放缩放吗？

Question

我们可以在Android中使用缩放手势检测器进行缩放缩放吗？

Answer 1

你可以用它

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class MyImageView extends View {

private static final int INVALID_POINTER_ID = -1;

    private Drawable mImage;
    private float mPosX;
    private float mPosY;

    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;

    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;

    public MyImageView(Context context) {
        this(context, null, 0);
    mImage=act.getResources().getDrawable(context.getResources().getIdentifier("imag­ename", "drawable", "packagename"));

        mImage.setBounds(0, 0, mImage.getIntrinsicWidth(), mImage.getIntrinsicHeight());
    }

    public MyImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // Let the ScaleGestureDetector inspect all events.
        mScaleDetector.onTouchEvent(ev);

        final int action = ev.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();

            mLastTouchX = x;
            mLastTouchY = y;
            mActivePointerId = ev.getPointerId(0);
            break;
        }

        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);

            // Only move if the ScaleGestureDetector isn't processing a gesture.
            if (!mScaleDetector.isInProgress()) {
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;

                mPosX += dx;
                mPosY += dy;

                invalidate();
            }

            mLastTouchX = x;
            mLastTouchY = y;

            break;
        }

        case MotionEvent.ACTION_UP: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_CANCEL: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_POINTER_UP: {
            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
                    >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
            final int pointerId = ev.getPointerId(pointerIndex);
            if (pointerId == mActivePointerId) {
                // This was our active pointer going up. Choose a new
                // active pointer and adjust accordingly.
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                mLastTouchX = ev.getX(newPointerIndex);
                mLastTouchY = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
            }
            break;
        }
        }

        return true;
    }

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

        canvas.save();
        Log.d("DEBUG", "X: "+mPosX+" Y: "+mPosY);
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        mImage.draw(canvas);
        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));

            invalidate();
            return true;
        }
    }

}

在你的电话中称呼这个 activity.setContentView(new MyImageView(this));

Answer 2

您可以创建一个可重用的类OnTouchListener来实现此目的.

public class MyScaleGestures implements OnTouchListener, OnScaleGestureListener {       
    private View view;
    private ScaleGestureDetector gestureScale;
    private float scaleFactor = 1;  
    private boolean inScale = false;

    public MyScaleGestures (Context c){ gestureScale = new ScaleGestureDetector(c, this); }

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        this.view = view; 
        gestureScale.onTouchEvent(event);
        return true;
    }   

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scaleFactor *= detector.getScaleFactor();
        scaleFactor = (scaleFactor < 1 ? 1 : scaleFactor); // prevent our view from becoming too small //
        scaleFactor = ((float)((int)(scaleFactor * 100))) / 100; // Change precision to help with jitter when user just rests their fingers //
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);
        return true;
    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        inScale = true;
        return true;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector) { inScale = false; }
}

然后将其指定为您View的OnTouchListener喜欢.

myView.setOnTouchListener(new MyScaleGestures(context));

如果要添加滚动功能,View则需要onScroll从OnGestureListener界面实现.您可以将此覆盖添加到MyScaleGestures类中以实现此目的.

@Override
public boolean onScroll(MotionEvent event1, MotionEvent event2, float x, float y) {
    float newX = view.getX();
    float newY = view.getY();
    if(!inScale){
        newX -= x;
        newY -= y;
    }
    WindowManager wm = (WindowManager) view.getContext().getSystemService(Context.WINDOW_SERVICE);
    Display d = wm.getDefaultDisplay();
    Point p = new Point();
    d.getSize(p);

    if (newX > (view.getWidth() * scaleFactor - p.x) / 2){
        newX = (view.getWidth() * scaleFactor - p.x) / 2;
    } else if (newX < -((view.getWidth() * scaleFactor - p.x) / 2)){
        newX = -((view.getWidth() * scaleFactor - p.x) / 2);
    }

    if (newY > (view.getHeight() * scaleFactor - p.y) / 2){
        newY = (view.getHeight() * scaleFactor - p.y) / 2;
    } else if (newY < -((view.getHeight() * scaleFactor - p.y) / 2)){
        newY = -((view.getHeight() * scaleFactor - p.y) / 2);
    }

    view.setX(newX);
    view.setY(newY);

    return true;
}

完成上述所有操作的最终结果将为您提供类似这样的课程:

public class StandardGestures implements OnTouchListener, OnGestureListener, OnDoubleTapListener, OnScaleGestureListener {
    private View view;
    private GestureDetector gesture;
    private ScaleGestureDetector gestureScale;
    private float scaleFactor = 1;
    private boolean inScale;

    public StandardGestures(Context c){
        gesture = new GestureDetector(c, this);
        gestureScale = new ScaleGestureDetector(c, this);
    }

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        this.view = view;
        gesture.onTouchEvent(event);
        gestureScale.onTouchEvent(event);
        return true;
    }

    @Override
    public boolean onDown(MotionEvent event) {
        return true;
    }

    @Override
    public boolean onFling(MotionEvent event1, MotionEvent event2, float x, float y) {
        return true;
    }

    @Override
    public void onLongPress(MotionEvent event) {
    }

    @Override
    public boolean onScroll(MotionEvent event1, MotionEvent event2, float x, float y) {
        float newX = view.getX();
        float newY = view.getY();
        if(!inScale){
            newX -= x;
            newY -= y;
        }
        WindowManager wm = (WindowManager) view.getContext().getSystemService(Context.WINDOW_SERVICE);
        Display d = wm.getDefaultDisplay();
        Point p = new Point();
        d.getSize(p);

        if (newX > (view.getWidth() * scaleFactor - p.x) / 2){
            newX = (view.getWidth() * scaleFactor - p.x) / 2;
        } else if (newX < -((view.getWidth() * scaleFactor - p.x) / 2)){
            newX = -((view.getWidth() * scaleFactor - p.x) / 2);
        }

        if (newY > (view.getHeight() * scaleFactor - p.y) / 2){
            newY = (view.getHeight() * scaleFactor - p.y) / 2;
        } else if (newY < -((view.getHeight() * scaleFactor - p.y) / 2)){
            newY = -((view.getHeight() * scaleFactor - p.y) / 2);
        }

        view.setX(newX);
        view.setY(newY);

        return true;
    }

    @Override
    public void onShowPress(MotionEvent event) {
    }

    @Override
    public boolean onSingleTapUp(MotionEvent event) {
        return true;
    }

    @Override
    public boolean onDoubleTap(MotionEvent event) {
        view.setVisibility(View.GONE);
        return true;
    }

    @Override
    public boolean onDoubleTapEvent(MotionEvent event) {
        return true;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent event) {
        return true;
    }

    @Override
    public boolean onScale(ScaleGestureDetector detector) {

        scaleFactor *= detector.getScaleFactor();
        scaleFactor = scaleFactor < 1 ? 1 : scaleFactor; // prevent our image from becoming too small
        scaleFactor = (float) (int) (scaleFactor * 100) / 100; // Change precision to help with jitter when user just rests their fingers //
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);
        onScroll(null, null, 0, 0); // call scroll to make sure our bounds are still ok //
        return true;
    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        inScale = true;
        return true;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
        inScale = false;
        onScroll(null, null, 0, 0); // call scroll to make sure our bounds are still ok //
    }
}

Answer 3

ScaleGestureDetector从Android 2.2(又名Froyo,API级别8)开始提供.请参阅:http://android-developers.blogspot.com/2010/06/making-sense-of-multitouch.html

在2.0/2.1中,您没有ScaleGestureDetector,但是您可以使用Ed Burnette的ZDNet博客条目提供双指缩放,Pieter888链接到上面:http://www.zdnet.com/blog/burnette/how -to-使用的多点触摸功能于机器人-2-部分-6-实现最捏变焦手势/ 1847