问题
I have made custom Relative Layout for Zooming with lot of research since I am new to Android and now I want to incorporate the panning/dragging which should behave like Imageview, that is, bound limits.
I am not using a matrix but the ScaleGestureDetector.SimpleOnScaleGestureListener. Now I want to incorporate the panning/dragging in the same.
How do I achieve drag/panning in my code? Here is my custom relative layout with proper commenting and understanding.
/*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : Custom Layout Zoom
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
package com.layoutzooming;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.GestureDetector.OnDoubleTapListener;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.view.ViewParent;
import android.widget.RelativeLayout;
public class ZoomLayout extends RelativeLayout implements OnDoubleTapListener, OnGestureListener{
//ScalingFactor i.e. Amount of Zoom
static float mScaleFactor = 1.0f;
// Maximum and Minimum Zoom
private static float MIN_ZOOM = 1.0f;
private static float MAX_ZOOM = 3.0f;
//Different Operation to be used
private final int NONE_OPERATION=0;
private final int ZOOM_OPERATION=2;
private float mWidth= 1280;
private float mHeight=800;
// Mode to select the operation
private int mode;
//Track X and Y coordinate of the finger when it first touches the screen
private float mInitialX = 0f;
private float mInitialY = 0f;
// Track the Bound of the Image after zoom to calculate the offset
static Rect mClipBound;
// mDetector to detect the scaleGesture for the pinch Zoom
private ScaleGestureDetector mDetector;
// mDoubleTapDetector to detect the double tap
private GestureDetector mDoubleTapDetector;
//Pivot point for Scaling
static float gx=0,gy=0;
/*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : Constructor is called when used via XML
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
public ZoomLayout(Context context, AttributeSet attrs) {
super(context, attrs);
setWillNotDraw(false);
mClipBound = new Rect();
// Intialize ScaleGestureDetector
mDetector = new ScaleGestureDetector(getContext(), new ZoomListener());
mDoubleTapDetector = new GestureDetector(context,this);
mDoubleTapDetector.setOnDoubleTapListener(this);
}
/*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : Constructor is called when used via code
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
public ZoomLayout(Context context) {
super(context);
setWillNotDraw(false);
mClipBound = new Rect();
// Intialize ScaleGestureDetector
mDetector = new ScaleGestureDetector(getContext(), new ZoomListener());
mDoubleTapDetector = new GestureDetector(context,this);
mDoubleTapDetector.setOnDoubleTapListener(this);
}
/*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : OnTouchEvent of the layout which handles all type of motion-events possible
* @ Returns : true - we are handling the touchEvent.
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
@Override
public boolean onTouchEvent(MotionEvent event) {
// Handles all type of motion-events possible
switch(event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
// Event occurs when the first finger is pressed on the Screen
Log.d("Print", "Event: Action_Down " );
mInitialX = event.getX();
mInitialY = event.getY();
break;
case MotionEvent.ACTION_POINTER_DOWN:
//Event occurs when the second finger is pressed down
Log.d("Print", "Event: Action_Pointer_Down " );
// If second finger is pressed on the screen with the first set the Mode to Zoom operation
mode=ZOOM_OPERATION;
break;
case MotionEvent.ACTION_UP:
//Event occurs when all the finger are taken of the screen
Log.d("Print", "Event: Action_UP " );
//If all the fingers are taken up there will be no operation
mode = NONE_OPERATION;
break;
}
// Give the event to the mDetector to get the scaling Factor
mDetector.onTouchEvent(event);
// Give the event to the mDoubleTapDetector for the doubleTap
mDoubleTapDetector.onTouchEvent(event);
return true;
}
/*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : By overriding the onInterceptTouchEvent y overriding the onInterceptTouchEvent,
* This allows you to watch events as they are dispatched to your children, and
* take ownership of the current gesture at any point. Allowing onTouchEvent of RelativeLayout to handle the
* all the motioin events .
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
onTouchEvent(ev);
return super.onInterceptTouchEvent(ev);
}
/*
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @descriptiont : invalidateChildInParent
*
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
@Override
public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
return super.invalidateChildInParent(location, dirty);
}
/*
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @descriptiont : Correctly sets the x,y position of the children relative to each other for different scale factors.
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
{
int count = getChildCount();
for(int i=0;i<count;i++){
View child = getChildAt(i);
if(child.getVisibility()!=GONE){
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)child.getLayoutParams();
child.layout(
(int)(params.leftMargin ),
(int)(params.topMargin ),
(int)((params.leftMargin + child.getMeasuredWidth()) ),
(int)((params.topMargin + child.getMeasuredHeight()))
);
}
}
}
/*
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @description : Called by draw to draw the ChildViews. We need to gained control before the children are
* drawn so that to apply the scaling Factors
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
@Override
protected void dispatchDraw(Canvas canvas) {
//Save the canvas to set the scaling factor returned from detector
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.scale(mScaleFactor, mScaleFactor,gx,gy);
super.dispatchDraw(canvas);
mClipBound = canvas.getClipBounds();
canvas.restore();
}
/*
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
* @name : ZoomListener
* @description : Class which defines the listener for ScaleGestureDetector
*
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*/
private class ZoomListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
// getting the scaleFactor from the detector
mScaleFactor *= detector.getScaleFactor(); // Gives the scaling factor from the previous scaling to the current
// Log.d("Print", "detector scaling Factor" + mScaleFactor);
gx = detector.getFocusX();
gy = detector.getFocusY();
// Limit the scale factor in the MIN and MAX bound
mScaleFactor= Math.max(Math.min(mScaleFactor, MAX_ZOOM),MIN_ZOOM);
// Log.d("Print", "Bounded scaling Factor" + mScaleFactor);
/*//Force canvas to redraw itself only if the one event is to happen (say Zooming only ) else do not invalidate here for multi operations
As what we de for scrolling or panning will not reflect here. So we will add this in onDraw method
invalidate();*/
// Here we are only zooming so invalidate has to be done
invalidate();
requestLayout();
// we have handle the onScale
return true;
}
}
@Override
public boolean onDoubleTap(MotionEvent e) {
// Make the mScaleFactor to its normal value
mScaleFactor=1.0f;
// Force the canvas to redraw itself again as the changes has been occured.
invalidate();
requestLayout();
return false;
}
@Override
public boolean onDoubleTapEvent(MotionEvent e) {
// Log.d("Print", "OnDoubleTapEvent");
return false;
}
@Override
public boolean onSingleTapConfirmed(MotionEvent e) {
// Log.d("Print", "OnSingleTap");
return false;
}
@Override
public boolean onDown(MotionEvent e) {
// TODO Auto-generated method stub
return false;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
return false;
}
@Override
public void onLongPress(MotionEvent e) {
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
return false;
}
@Override
public void onShowPress(MotionEvent e) {
}
@Override
public boolean onSingleTapUp(MotionEvent e) {
return false;
}
}
回答1:
I am doing the same thing. I put the following in the onTouchEvent ACTION_UP event.
if (mScaleFactor > 1)
{
gx = gx - (event.getX() - mInitialX);
gy = gy - (event.getY() - mInitialY);
invalidate();
requestLayout();
}
Where mScaleFactor, mInitialX, mInitialY are from the ScaleGestureDetector onScale function. The scaling is working well. Once scaled up though I cannot select views on the layout. Sometimes it works and sometimes it doesn't.
来源：https://stackoverflow.com/questions/10257321/scroll-panning-or-drag-in-custom-layout