canvas.scale（）无法正常工作

Question

I have the following code, that when I pinch in the screen it will join/split the objects.

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.view.ScaleGestureDetector.SimpleOnScaleGestureListener;
import android.view.animation.ScaleAnimation;
import android.widget.RelativeLayout;

public class GDTicketGroupView extends RelativeLayout{

//Constants
int kNumberofTickets = 3;
int kTicketWidth = 225;
int kTicketHeight = 100;
int kMarginLeft = 12;
int kMarginTop = 12;
int kMarginRight = 12;
int kMarginBottom = 12;
float kMinScale = 0.5f;
float kNormalScale = 1.0f;
float kMaxScale = 1.2f; 
//Variables
float mScaleFactor = 1;
Boolean scaling = false;
RelativeLayout gestureview;
//Temporary
float tmpScale = 1; 
//Objects
ScaleGestureDetector scaleGestureDetector;
GDTicketView Ticket;

public GDTicketGroupView(Context context) {
    super(context);

    //Creating the GestureDetector
    scaleGestureDetector = new ScaleGestureDetector(context, new simpleOnScaleGestureListener());

    //Gesture View
    gestureview = new RelativeLayout(context);
    RelativeLayout.LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    gestureview.setLayoutParams(params);

    //Adding SubViews
    addTickets(context);

    //Only for Testing
    setBackgroundColor(Color.RED);
}
public GDTicketGroupView(Context context, AttributeSet attrs) {
    super(context, attrs);

    //Creating the GestureDetector
    scaleGestureDetector = new ScaleGestureDetector(context, new simpleOnScaleGestureListener());

    //Adding SubViews
    addTickets(context);

    //Only for Testing
    setBackgroundColor(Color.RED);
}
public GDTicketGroupView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    //Creating the GestureDetector
    scaleGestureDetector = new ScaleGestureDetector(context, new simpleOnScaleGestureListener());

    //Adding SubViews
    addTickets(context);

    //Only for Testing
    setBackgroundColor(Color.RED);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
    scaleGestureDetector.onTouchEvent(event);
    return true;
}   
@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.save();
    if (scaling == true){
        if (mScaleFactor >= kMinScale * tmpScale && mScaleFactor < kMaxScale * tmpScale){
            canvas.scale(kNormalScale, mScaleFactor);
            Log.d("DEBUG", "mScaleFactor >= kMinScale * tmpScale && mScaleFactor < kMaxScale * tmpScale"+" is True");
        }
    }
    canvas.restore();
    Log.d("DEBUG", "onDraw is running");
}
public class simpleOnScaleGestureListener extends SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor = detector.getScaleFactor();
        Log.d("DEBUG", "mScaleFactor is "+mScaleFactor+", so Scale is Running");
        scaling = true;
        invalidate();
    return true;
    }
    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
        //Expand Animation
        if (mScaleFactor >= kMinScale){
            ScaleAnimation anim = new ScaleAnimation(1, 1, 1, 1);
            startAnimation(anim);
            tmpScale=1;
            adjustTickets();
        } else if (mScaleFactor < kMinScale){
            ScaleAnimation anim = new ScaleAnimation(1, 1, mScaleFactor, 1);
            startAnimation(anim);
            tmpScale = kMinScale;
            adjustTickets();
        }
        scaling = false;
        Log.d("DEBUG", "Scale have ended");
    }
}   
public void adjustTickets(){
    //First Ticket
    GDTicketView firstTicket = (GDTicketView)findViewWithTag(1);

    //Last Ticket
    GDTicketView lastTicket = (GDTicketView)findViewWithTag(kNumberofTickets);

    // Creating average variables       
    int totalY = firstTicket.getTop() + lastTicket.getTop();
    int parcialY = totalY / (kNumberofTickets - 1);

    // The rest of the tickets
    for (int i = 2; i <= kNumberofTickets - 1; i++) {
        GDTicketView ticketBeingAdjusted = (GDTicketView)findViewWithTag(i);
        RelativeLayout.LayoutParams params = new LayoutParams(kTicketWidth, kTicketHeight);
        params.setMargins(kMarginLeft, (i - 1) * parcialY, kMarginRight, kMarginBottom);
        ticketBeingAdjusted.setLayoutParams(params);

    }
}
public void addTickets(Context context){
    for(int i = 1; i <= kNumberofTickets; i++){
        Ticket = new GDTicketView(context);
        RelativeLayout.LayoutParams params = new LayoutParams(kTicketWidth, kTicketHeight);
        params.setMargins(kMarginLeft, kMarginTop, kMarginRight, kMarginBottom);
        params.addRule(CENTER_HORIZONTAL);
        if (i != 1){
            params.setMargins(kMarginLeft, kMarginTop+kTicketHeight, kMarginRight, kMarginBottom);
            GDTicketView ticket = (GDTicketView)findViewWithTag(i-1);
            if (ticket.getId() == View.NO_ID){
                ticket.setId(i);
            }
            params.addRule(RelativeLayout.ALIGN_TOP, ticket.getId());
        }
        Ticket.setTag(i);
        Ticket.setBackgroundColor(Color.GREEN);
        Log.d("INIT", "Ticket View " + i +" added correctly");
        addView(Ticket, params);
    }
}
}

In the onDraw method, whan the mScaleFactor change, the view don't change the height, but in the logcat mScaleFactor it's not 1 so, I think that something don't work right.

Answer 1

You call these methods in order:

save()
scale()
restore()

But you don't draw anything after calling scale() . Your code changes the scale factor and then restores it back to the original scale factor of 1,1.

I see that you also use two ScaleAnimation instances. One doesn't do anything since it scales from 1,1 to 1,1. The other one should work though.