我正在尝试使用大型Canvas（大小为1440 * 2560）开发绘图应用程序。我已经实现了多点触控（双指）捏缩放和平移。
问题：
在Canvas上执行放大之后
我尝试缩小或平移此画布，首先将画布移动一定距离（左侧），然后进行滚动或缩放。
实施：
为了实现此应用程序，我创建了大小为3180 * 5420的自定义视图。我已将Canvas放置在此自定义视图的中心。要实现 Pinch-缩放我正在使用 ScaleGestureDetector 。对于平移我使用的是 ScrollView 。
代码：
自定义视图
public class DrawingView extends View {
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
private static Bitmap RedoIt= Bitmap.createBitmap(1440,2560, Config.ARGB_8888);;
private static Canvas mcanvas=new Canvas(RedoIt);
DrawingView drawview=(DrawingView)findViewById(R.id.single_touch_view);
@SuppressLint("NewApi")
public DrawingView(Context context, AttributeSet attrs) {
super(context, attrs);
paint.setAntiAlias(true);
paint.setStrokeWidth(5f);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
} }
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
pathCounter++;
g.setFlag(false);
canvas.scale(mScaleFactor, mScaleFactor,scalePointX,scalePointY);
canvas.drawBitmap(RedoIt,870,1430, null); // to place canvas at center
if(g.getstr().equals("OLIVE"))
setColorint(128,128,0);
else if(g.getstr().equals("ORANGE"))
setColorint(255,153,0);
else if(g.getstr().equals("BROWN"))
setColorint(165,42,42);
else
setColor(g.getstr());
paths.add(path);
colorsMap.put(path,paint.getColor());
canvas.restore();
}
public boolean onTouchEvent(MotionEvent event) {
// Get the coordinates of the touch event.
float eventX = event.getX()-870;
float eventY = event.getY()-1430;
**// for Pinch Zoom and panning**
mode=1;
switch (event.getAction()& MotionEvent.ACTION_MASK) {
case Mot
ionEvent.ACTION_DOWN:
x1=event.getX(pointerIndex)-870;
y1=event.getY(pointerIndex)-1430;
return true;
case MotionEvent.ACTION_POINTER_DOWN:
mSecondPointerId = event.getPointerId(1);
counter=0;
pointerIndex2 = event.findPointerIndex(mSecondPointerId);
x2=event.getX(pointerIndex2)-870;
y2=event.getY(pointerIndex2)-1430;
mScaleDetector = new ScaleGestureDetector(DrawingView.this.getContext() , new ScaleListener());
dist1=(float) Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
case MotionEvent.ACTION_MOVE:
{
x3=event.getX(pointerIndex)-870;
y3=event.getY(pointerIndex)-1430;
x4=event.getX(pointerIndex2)-870;
y4=event.getY(pointerIndex2)-1430;
dist2=(float) Math.sqrt(Math.pow(x3-x4,2)+Math.pow(y3-y4,2));
counter++;
if(counter==4){
**//To detect two finger Panning action**
if(Math.abs(dist1-dist2)<5){
flag=true; // Enable panning
getParent().requestDisallowInterceptTouchEvent(false);
}
}}
break;
case MotionEvent.ACTION_POINTER_UP:
mode =1;
flag2=false;
getParent().requestDisallowInterceptTouchEvent(true);
return true;
default:
return false;
}
invalidate();
if(flag==false)// no panning action detected
{
flagZoom=true;
mScaleDetector.onTouchEvent(event);
getParent().requestDisallowInterceptTouchEvent(true);
}
return true;
}
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
public boolean onScaleBegin(ScaleGestureDetector detector) {
getParent().requestDisallowInterceptTouchEvent(true);
super.onScaleBegin(detector);
return true;
}
public boolean onScale(ScaleGestureDetector detector) {
scalePointX = detector.getFocusX();
scalePointY = detector.getFocusY();
getParent().requestDisallowInterceptTouchEvent(true);
mScaleFactor *= detector.getScaleFactor();
mScaleFactor = Math.max(0.25f, Math.min(mScaleFactor, 2.0f));
invalidate();
return true;
}
public void onScaleEnd(ScaleGestureDetector detector1) {
getParent().requestDisallowInterceptTouchEvent(false);
super.onScaleEnd(detector1);
}
}
自定义视图布局文件：
<HorizontalScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:fadeScrollbars="false"
android:id="@+id/horizontalscrollview"
>
<ScrollView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:fadeScrollbars="false"
android:id="@+id/scrollview">
<AbsoluteLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<!-- This is the view on which we will draw. -->
<view
android:layout_width="3180px"
android:layout_height="5420px"
android:scaleType="matrix"
android:layout_x="0px"
android:layout_y="0px"
class="com.example.DrawingView"
android:id="@+id/single_touch_view"
android:scrollbars="horizontal|vertical"
android:background="@drawable/brown_wood" />
</AbsoluteLayout>
</ScrollView>
</HorizontalScrollView>
由于我始终保持 ScaleGesturedetector 处于活动状态，这可能是此问题的可能原因。有没有办法禁用 ScaleGesturedetector ？或者代码中的任何其他修改都是必需的。