[转载]Android通过手势(多点)缩放和拖拽图片
2012-03-26 01:20
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[b]原文地址:[/b]Android通过手势(多点)缩放和拖拽图片 作者:望夜
在MotionEvent中有两个事件值得注意一下,分别是ACTION_DOWN和ACTION_POINTER_DOWN。
ACTION_DOWN:这个很好理解,当屏幕检测到有手指按下之后就触发到这个事件。
ACTION_POINTER_DOWN:这个是实现多点的关键,当屏幕检测到有多个手指同时按下之后,就触发了这个事件。
通过getAction()可以获得当前屏幕的事件类型:ACTION_DOWN, ACTION_MOVE, ACTION_UP, orACTION_CANCEL。但是如果像获得如上的ACTION_POINTER_DOWN,则得和ACTION_MASK相与才能得到ACTION_POINTER_DOWN事件。
所以我们运用一个switch-case结构就可以实现对图片进行拖拽或缩放,而缩放的只要思想是在移动的过程中计算两个点之间的距离,然后再进行缩放。
上代码:
@Override
publicboolean onTouch(View v, MotionEvent event) {
ImageViewview = (ImageView) v;
dumpEvent(event);
// Handletouch events here...
switch(event.getAction() & MotionEvent.ACTION_MASK){
caseMotionEvent.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;
caseMotionEvent.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");
}//ACTION_DOWN, ACTION_MOVE, ACTION_UP, or ACTION_CANCEL.
break;
caseMotionEvent.ACTION_UP:
caseMotionEvent.ACTION_POINTER_UP:
mode =NONE;
break;
caseMotionEvent.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);
returntrue; // indicate event was handled
}
private voiddumpEvent(MotionEvent event) {
Stringnames[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",
"POINTER_DOWN","POINTER_UP", "7?", "8?", "9?" };
StringBuilder sb = new StringBuilder();
int action= event.getAction();
intactionCode = 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());
}
复制代码
求两点间距离:
private float spacing(MotionEvent event) {
float x =event.getX(0) - event.getX(1);
float y =event.getY(0) - event.getY(1);
returnFloatMath.sqrt(x * x + y * y);
}
复制代码
求两点间中点:
private voidmidPoint(PointF point, MotionEvent event) {
float x =event.getX(0) + event.getX(1);
在MotionEvent中有两个事件值得注意一下,分别是ACTION_DOWN和ACTION_POINTER_DOWN。
ACTION_DOWN:这个很好理解,当屏幕检测到有手指按下之后就触发到这个事件。
ACTION_POINTER_DOWN:这个是实现多点的关键,当屏幕检测到有多个手指同时按下之后,就触发了这个事件。
通过getAction()可以获得当前屏幕的事件类型:ACTION_DOWN, ACTION_MOVE, ACTION_UP, orACTION_CANCEL。但是如果像获得如上的ACTION_POINTER_DOWN,则得和ACTION_MASK相与才能得到ACTION_POINTER_DOWN事件。
所以我们运用一个switch-case结构就可以实现对图片进行拖拽或缩放,而缩放的只要思想是在移动的过程中计算两个点之间的距离,然后再进行缩放。
上代码:
@Override
publicboolean onTouch(View v, MotionEvent event) {
ImageViewview = (ImageView) v;
dumpEvent(event);
// Handletouch events here...
switch(event.getAction() & MotionEvent.ACTION_MASK){
caseMotionEvent.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;
caseMotionEvent.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");
}//ACTION_DOWN, ACTION_MOVE, ACTION_UP, or ACTION_CANCEL.
break;
caseMotionEvent.ACTION_UP:
caseMotionEvent.ACTION_POINTER_UP:
mode =NONE;
break;
caseMotionEvent.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);
returntrue; // indicate event was handled
}
private voiddumpEvent(MotionEvent event) {
Stringnames[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",
"POINTER_DOWN","POINTER_UP", "7?", "8?", "9?" };
StringBuilder sb = new StringBuilder();
int action= event.getAction();
intactionCode = 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());
}
复制代码
求两点间距离:
private float spacing(MotionEvent event) {
float x =event.getX(0) - event.getX(1);
float y =event.getY(0) - event.getY(1);
returnFloatMath.sqrt(x * x + y * y);
}
复制代码
求两点间中点:
private voidmidPoint(PointF point, MotionEvent event) {
float x =event.getX(0) + event.getX(1);
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