Android之MotionEvent学习
getAction()方法返回的是int类型，用到的只有低16位（0x0000），其中：低八位是动作的类型，高8位是触摸点索引值的表示
1、如果mAction的值是0x0000，则表示是第一个触控点的ACTION_DOWN操作。
如果mAction的值是0x0100，则表示是第二个触控点的ACTION_DOWN操作。
第三个的ACTION_DOWN呢？相信你可以推出来是0x0200。
总而言之，mAction时的低8位（也就是0-7位）是动作类型信息。
mAction的8-15位呢，是触控点的索引信息。（即表示是哪一个触控点的事件）。
2、应用1）获得动作类型： int action = event.getAction() & ACTION_MASK 或者使用 getActionMasked()
2）获得触摸点索引类型： int pointerIndex = (event.getAction() & ACTION_POINTER_INDEX_MASK ) >> ACTION_POINTER_INDEX_SHIFT
或者使用 getActionIndex()
3）getAction()与getActionMasked()区别
/**
* Bit mask of the parts of the action code that are the action itself.
*/
public static final int ACTION_MASK = 0xff;
/**
* Return the kind of action being performed.
* Consider using {@link #getActionMasked} and {@link #getActionIndex} to retrieve
* the separate masked action and pointer index.
* @return The action, such as {@link #ACTION_DOWN} or
* the combination of {@link #ACTION_POINTER_DOWN} with a shifted pointer index.
*/
public final int getAction() {
return nativeGetAction(mNativePtr);
}
/**
* Return the masked action being performed, without pointer index information.
* Use {@link #getActionIndex} to return the index associated with pointer actions.
* @return The action, such as {@link #ACTION_DOWN} or {@link #ACTION_POINTER_DOWN}.
*/
public final int getActionMasked() {
return nativeGetAction(mNativePtr) & ACTION_MASK;
}
4）getActionIndex()源码：
/**
* For {@link #ACTION_POINTER_DOWN} or {@link #ACTION_POINTER_UP}
* as returned by {@link #getActionMasked}, this returns the associated
* pointer index.
* The index may be used with {@link #getPointerId(int)},
* {@link #getX(int)}, {@link #getY(int)}, {@link #getPressure(int)},
* and {@link #getSize(int)} to get information about the pointer that has
* gone down or up.
* @return The index associated with the action.
*/
public final int getActionIndex() {
return (nativeGetAction(mNativePtr) & ACTION_POINTER_INDEX_MASK)
>> ACTION_POINTER_INDEX_SHIFT;
}
其中ACTION_POINTER_INDEX_MASK，ACTION_POINTER_INDEX_SHIFT分别为：
/**
* Bits in the action code that represent a pointer index, used with
* {@link #ACTION_POINTER_DOWN} and {@link #ACTION_POINTER_UP}. Shifting
* down by {@link #ACTION_POINTER_INDEX_SHIFT} provides the actual pointer
* index where the data for the pointer going up or down can be found; you can
* get its identifier with {@link #getPointerId(int)} and the actual
* data with {@link #getX(int)} etc.
*/
public static final int ACTION_POINTER_INDEX_MASK = 0xff00;
/**
* Bit shift for the action bits holding the pointer index as
* defined by {@link #ACTION_POINTER_INDEX_MASK}.
*/
public static final int ACTION_POINTER_INDEX_SHIFT = 8;
5）getAction()常用动作：
public static final int ACTION_DOWN = 0;//单点触摸动作
public static final int ACTION_UP = 1;//单点触摸离开动作
public static final int ACTION_MOVE = 2;//触摸点移动动作
public static final int ACTION_CANCEL = 3;//触摸动作取消
public static final int ACTION_OUTSIDE = 4;//触摸动作超出边界
public static final int ACTION_POINTER_DOWN = 5;//多点触摸动作
public static final int ACTION_POINTER_UP = 6;//多点离开动作
以下是一些非touch事件：
public static final int ACTION_HOVER_MOVE = 7;
public static final int ACTION_SCROLL = 8;
public static final int ACTION_HOVER_ENTER = 9;
public static final int ACTION_HOVER_EXIT = 10;
6）判断是否为多点触控：event.getPointerCount() > 1
/* The number of pointers of data contained in this event. Always >= 1.*/
public final int getPointerCount() {
return nativeGetPointerCount(mNativePtr);
}
7）获得触摸事件的X,Y坐标
float x = event.getXPrecision()*event.getX()+event.getX(); float y = event.getYPrecision()*event.getY()+event.getY();
单击事件采用getX(),getY();多点触摸事件采用getX(int pointerIndex)，getY(int pointerIndex)，pointerIndex为多点触摸的指针索引
I . getX(),getY()源码：
/*{@link #getX(int)} for the first pointer index (may be an arbitrary pointer identifier).*/
public final float getX() {
return nativeGetAxisValue(mNativePtr, AXIS_X, 0, HISTORY_CURRENT);
}
public final float getY() {
return nativeGetAxisValue(mNativePtr, AXIS_Y, 0, HISTORY_CURRENT);
}
II . getX(int),getY(int)源码：
/**
* Returns the X coordinate of this event for the given pointer
* <em>index</em> (use {@link #getPointerId(int)} to find the pointer
* identifier for this index).
* Whole numbers are pixels; the
* value may have a fraction for input devices that are sub-pixel precise.
* @param pointerIndex Raw index of pointer to retrieve. Value may be from 0
* (the first pointer that is down) to {@link #getPointerCount()}-1.
*/
public final float getX(int pointerIndex) {
return nativeGetAxisValue(mNativePtr, AXIS_X, pointerIndex, HISTORY_CURRENT);
}
public final float getY(int pointerIndex) {
return nativeGetAxisValue(mNativePtr, AXIS_Y, pointerIndex, HISTORY_CURRENT);
}
III . getXPrecision(),getYPrecision()源码：
/**
* Return the precision of the X coordinates being reported. You can
* multiply this number with {@link #getX} to find the actual hardware
* value of the X coordinate.
* @return Returns the precision of X coordinates being reported.
*/
public final float getXPrecision() {
return nativeGetXPrecision(mNativePtr);
}
public final float getYPrecision() {
return nativeGetYPrecision(mNativePtr);
}
8）MotionEvent的getX()，getY()与getRawX(),getRawY()区别
getRawX()和getRawY()获得的是相对屏幕的位置，getX()和getY()获得的永远是相对view的触摸位置坐标（这两个值不会超过view的长度和宽度）。
RawX,RawY 相对于屏幕位置坐标
X,Y 相对于容器的位置坐标
getRawX()获取的是屏幕上的原生（original raw)x坐标，而getX(int pointerIndex)只是说获取的是指定的触控点坐标，getX()就是获取第一个触控点的坐标。所以， getRawX()就是说，获取的是相对于屏幕左上角的x坐标，而getX()是获取相对控件左上角的x坐标。
/**
* Returns the original raw X coordinate of this event. For touch
* events on the screen, this is the original location of the event
* on the screen, before it had been adjusted for the containing window
* and views.
*/
public final float getRawX() {
return nativeGetRawAxisValue(mNativePtr, AXIS_X, 0, HISTORY_CURRENT);
}
public final float getRawY() {
return nativeGetRawAxisValue(mNativePtr, AXIS_Y, 0, HISTORY_CURRENT);
}
9）应用实例：
@Override
public boolean onTouchEvent(MotionEvent event)
{
int action = event.getActionMasked();
switch (action) {
//单点触控
case MotionEvent.ACTION_DOWN:
Toast.makeText(this, "ACTION_DOWN", Toast.LENGTH_SHORT).show();
Log.e("ACTION_DOWN", "*****************************************************");
Log.w("ACTION_DOWN", "getAction : " + event.getAction());
Log.i("ACTION_DOWN", "getActionMasked: " + event.getActionMasked());
float posX = event.getX();
float posY = event.getY();
Log.i("ACTION_DOWN", "getX :: (" + posX + "," + posY + ")");
posX = event.getXPrecision();
posY = event.getYPrecision();
Log.i("ACTION_DOWN", "getPrecision:: (" + posX + "," + posY + ")");
posX = event.getXPrecision() * event.getX() + event.getX();
posY = event.getYPrecision() * event.getY() + event.getY();
Log.i("ACTION_DOWN", "getTotal :: (" + posX + "," + posY + ")");
posX = event.getRawX();
posY = event.getRawY();
Log.i("ACTION_DOWN", "getRaw :: (" + posX + "," + posY + ")");
return true;
//多点触控
case MotionEvent.ACTION_POINTER_DOWN:
Toast.makeText(this, "ACTION_POINTER_DOWN", Toast.LENGTH_SHORT).show();
Log.e("ACTION_POINTER_DOWN", "*****************************************************");
Log.i("ACTION_POINTER_DOWN", "getPointerCount: " + event.getPointerCount());
Log.w("ACTION_POINTER_DOWN", "getAction : " + event.getAction());
Log.i("ACTION_POINTER_DOWN", "getActionMasked: " + event.getActionMasked());
Log.i("ACTION_POINTER_DOWN", "getActionIndex : " + event.getActionIndex());
Log.i("ACTION_POINTER_DOWN", "getActionId : " + (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK));
Log.w("ACTION_POINTER_DOWN", "getPointerId : " + event.getPointerId(event.getActionIndex()));
Log.w("ACTION_POINTER_DOWN", "------------------------------------------------------");
float posX0 = event.getX(0);
float posX1 = event.getX(1);
float posY0 = event.getY(0);
float posY1 = event.getY(1);
Log.i("ACTION_POINTER_DOWN", "Pointer1:: (" + posX0 + "," + posY0 + ")");
Log.i("ACTION_POINTER_DOWN", "Pointer2:: (" + posX1 + "," + posY1 + ")");
return true;
default:
return super.onTouchEvent(event);
}
}
测试结果：
