通过手势实现Android ImageView 缩放
方法一：
将以下代码写到MulitPointTouchListener.java中，然后对你相应的图片进行OnTouchListener。
例如：imageView.setOnTouchListener(new MulitPointTouchListener ());
在xml中要将ImageView的缩放格式改成Matrix
例如：android:scaleType="matrix"
这样就可以实现图片的缩放了
下面是MulitPointTouchListener.java代码：
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public
class
MulitPointTouchListener
implements
OnTouchListener {
private
static
final
String TAG =
"Touch"
;
// These matrices will be used to move and zoom image
Matrix matrix =
new
Matrix();
Matrix savedMatrix =
new
Matrix();
// We can be in one of these 3 states
static
final
int
NONE =
0
;
static
final
int
DRAG =
1
;
static
final
int
ZOOM =
2
;
int
mode = NONE;
// Remember some things for zooming
PointF start =
new
PointF();
PointF mid =
new
PointF();
float
oldDist = 1f;
@Override
public
boolean
onTouch(View v, MotionEvent event) {
ImageView view = (ImageView) v;
// Log.e("view_width",
// view.getImageMatrix()..toString()+"*"+v.getWidth());
// Dump touch event to log
dumpEvent(event);
// Handle touch events here...
switch
(event.getAction() & MotionEvent.ACTION_MASK) {
case
MotionEvent.ACTION_DOWN:
matrix.set(view.getImageMatrix());
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
//Log.d(TAG, "mode=DRAG");
mode = DRAG;
//Log.d(TAG, "mode=NONE");
break
;
case
MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
//Log.d(TAG, "oldDist=" + oldDist);
if
(oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
//Log.d(TAG, "mode=ZOOM");
}
break
;
case
MotionEvent.ACTION_UP:
case
MotionEvent.ACTION_POINTER_UP:
mode = NONE;
//Log.e("view.getWidth", view.getWidth() + "");
//Log.e("view.getHeight", view.getHeight() + "");
break
;
case
MotionEvent.ACTION_MOVE:
if
(mode == DRAG) {
// ...
matrix.set(savedMatrix);
matrix.postTranslate(event.getX() - start.x, event.getY()
- start.y);
}
else
if
(mode == ZOOM) {
float
newDist = spacing(event);
//Log.d(TAG, "newDist=" + newDist);
if
(newDist > 10f) {
matrix.set(savedMatrix);
float
scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break
;
}
view.setImageMatrix(matrix);
return
true
;
// indicate event was handled
}
private
void
dumpEvent(MotionEvent event) {
String names[] = {
"DOWN"
,
"UP"
,
"MOVE"
,
"CANCEL"
,
"OUTSIDE"
,
"POINTER_DOWN"
,
"POINTER_UP"
,
"7?"
,
"8?"
,
"9?"
};
StringBuilder sb =
new
StringBuilder();
int
action = event.getAction();
int
actionCode = action & MotionEvent.ACTION_MASK;
sb.append(
"event ACTION_"
).append(names[actionCode]);
if
(actionCode == MotionEvent.ACTION_POINTER_DOWN
|| actionCode == MotionEvent.ACTION_POINTER_UP) {
sb.append(
"(pid "
).append(
action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
sb.append(
")"
);
}
sb.append(
"["
);
for
(
int
i =
0
; i < event.getPointerCount(); i++) {
sb.append(
"#"
).append(i);
sb.append(
"(pid "
).append(event.getPointerId(i));
sb.append(
")="
).append((
int
) event.getX(i));
sb.append(
","
).append((
int
) event.getY(i));
if
(i +
1
< event.getPointerCount())
sb.append(
";"
);
}
sb.append(
"]"
);
//Log.d(TAG, sb.toString());
}
private
float
spacing(MotionEvent event) {
float
x = event.getX(
0
) - event.getX(
1
);
float
y = event.getY(
0
) - event.getY(
1
);
return
FloatMath.sqrt(x * x + y * y);
}
private
void
midPoint(PointF point, MotionEvent event) {
float
x = event.getX(
0
) + event.getX(
1
);
float
y = event.getY(
0
) + event.getY(
1
);
point.set(x /
2
, y /
2
);
}
}
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方法二：自定义一个ImageView，例如TouchImageView：
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import
android.content.Context;
import
android.graphics.Matrix;
import
android.graphics.PointF;
import
android.graphics.drawable.Drawable;
import
android.util.AttributeSet;
import
android.util.Log;
import
android.view.MotionEvent;
import
android.view.ScaleGestureDetector;
import
android.view.View;
import
android.widget.ImageView;
public
class
TouchImageView
extends
ImageView {
Matrix matrix;
// We can be in one of these 3 states
static
final
int
NONE =
0
;
static
final
int
DRAG =
1
;
static
final
int
ZOOM =
2
;
int
mode = NONE;
// Remember some things for zooming
PointF last =
new
PointF();
PointF start =
new
PointF();
float
minScale = 1f;
float
maxScale = 3f;
float
[] m;
int
viewWidth, viewHeight;
static
final
int
CLICK =
3
;
float
saveScale = 1f;
protected
float
origWidth, origHeight;
int
oldMeasuredWidth, oldMeasuredHeight;
ScaleGestureDetector mScaleDetector;
Context context;
public
TouchImageView(Context context) {
super
(context);
sharedConstructing(context);
}
public
TouchImageView(Context context, AttributeSet attrs) {
super
(context, attrs);
sharedConstructing(context);
}
private
void
sharedConstructing(Context context) {
super
.setClickable(
true
);
this
.context = context;
mScaleDetector =
new
ScaleGestureDetector(context,
new
ScaleListener());
matrix =
new
Matrix();
m =
new
float
[
9
];
setImageMatrix(matrix);
setScaleType(ScaleType.MATRIX);
setOnTouchListener(
new
OnTouchListener() {
@Override
public
boolean
onTouch(View v, MotionEvent event) {
mScaleDetector.onTouchEvent(event);
PointF curr =
new
PointF(event.getX(), event.getY());
switch
(event.getAction()) {
case
MotionEvent.ACTION_DOWN:
last.set(curr);
start.set(last);
mode = DRAG;
break
;
case
MotionEvent.ACTION_MOVE:
if
(mode == DRAG) {
float
deltaX = curr.x - last.x;
float
deltaY = curr.y - last.y;
float
fixTransX = getFixDragTrans(deltaX, viewWidth, origWidth * saveScale);
float
fixTransY = getFixDragTrans(deltaY, viewHeight, origHeight * saveScale);
matrix.postTranslate(fixTransX, fixTransY);
fixTrans();
last.set(curr.x, curr.y);
}
break
;
case
MotionEvent.ACTION_UP:
mode = NONE;
int
xDiff = (
int
) Math.abs(curr.x - start.x);
int
yDiff = (
int
) Math.abs(curr.y - start.y);
if
(xDiff < CLICK && yDiff < CLICK)
performClick();
break
;
case
MotionEvent.ACTION_POINTER_UP:
mode = NONE;
break
;
}
setImageMatrix(matrix);
invalidate();
return
true
;
// indicate event was handled
}
});
}
public
void
setMaxZoom(
float
x) {
maxScale = x;
}
private
class
ScaleListener
extends
ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public
boolean
onScaleBegin(ScaleGestureDetector detector) {
mode = ZOOM;
return
true
;
}
@Override
public
boolean
onScale(ScaleGestureDetector detector) {
float
mScaleFactor = detector.getScaleFactor();
float
origScale = saveScale;
saveScale *= mScaleFactor;
if
(saveScale > maxScale) {
saveScale = maxScale;
mScaleFactor = maxScale / origScale;
}
else
if
(saveScale < minScale) {
saveScale = minScale;
mScaleFactor = minScale / origScale;
}
if
(origWidth * saveScale <= viewWidth || origHeight * saveScale <= viewHeight)
matrix.postScale(mScaleFactor, mScaleFactor, viewWidth /
2
, viewHeight /
2
);
else
matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY());
fixTrans();
return
true
;
}
}
void
fixTrans() {
matrix.getValues(m);
float
transX = m[Matrix.MTRANS_X];
float
transY = m[Matrix.MTRANS_Y];
float
fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale);
float
fixTransY = getFixTrans(transY, viewHeight, origHeight * saveScale);
if
(fixTransX !=
0
|| fixTransY !=
0
)
matrix.postTranslate(fixTransX, fixTransY);
}
float
getFixTrans(
float
trans,
float
viewSize,
float
contentSize) {
float
minTrans, maxTrans;
if
(contentSize <= viewSize) {
minTrans =
0
;
maxTrans = viewSize - contentSize;
}
else
{
minTrans = viewSize - contentSize;
maxTrans =
0
;
}
if
(trans < minTrans)
return
-trans + minTrans;
if
(trans > maxTrans)
return
-trans + maxTrans;
return
0
;
}
float
getFixDragTrans(
float
delta,
float
viewSize,
float
contentSize) {
if
(contentSize <= viewSize) {
return
0
;
}
return
delta;
}
@Override
protected
void
onMeasure(
int
widthMeasureSpec,
int
heightMeasureSpec) {
super
.onMeasure(widthMeasureSpec, heightMeasureSpec);
viewWidth = MeasureSpec.getSize(widthMeasureSpec);
viewHeight = MeasureSpec.getSize(heightMeasureSpec);
//
// Rescales image on rotation
//
if
(oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight
|| viewWidth ==
0
|| viewHeight ==
0
)
return
;
oldMeasuredHeight = viewHeight;
oldMeasuredWidth = viewWidth;
if
(saveScale ==
1
) {
//Fit to screen.
float
scale;
Drawable drawable = getDrawable();
if
(drawable ==
null
|| drawable.getIntrinsicWidth() ==
0
|| drawable.getIntrinsicHeight() ==
0
)
return
;
int
bmWidth = drawable.getIntrinsicWidth();
int
bmHeight = drawable.getIntrinsicHeight();
Log.d(
"bmSize"
,
"bmWidth: "
+ bmWidth +
" bmHeight : "
+ bmHeight);
float
scaleX = (
float
) viewWidth / (
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