问：您好，我需要计算多点触摸中每个手指所覆盖的像素。当手指一一向下滑动时，它应该加上像素数，而向上指的手指应该减去该手指的像素数。我不知道它到底有什么问题。请帮助我，我坚持下去。
public class MainActivity extends AppCompatActivity {
private static final int INVALID_POINTER_ID = -1;
private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;
private float mPosX;
private float mPosY;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
float TouchMajor=0.0f;
float TouchMinor=0.0f;
//float Size = 0.0f;
Boolean IsRightSideActive = false;
Boolean IsLeftSideActive = false;
float RightPixSize=0.0f;
float LeftPixSize=0.0f;
float RightPixChange = 0.0f;
float LeftPixChange = 0.0f;
float Pressure = 0.0f;
String Orientaation = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Image img = new Image(getApplicationContext());
setContentView(R.layout.activity_main);
final ImageView MyimageView = (ImageView)findViewById(R.id.imageView);
final TextView LeftPixelView = (TextView)findViewById(R.id.LeftPixelView);
final TextView RightPixelView = (TextView)findViewById(R.id.RightPixelView);
final TextView PressureView = (TextView)findViewById(R.id.PressureView);
final TextView OrientationView = (TextView)findViewById(R.id.OrientationView);
final Display display = getWindowManager().getDefaultDisplay();
final int ScreenWidth = display.getWidth();
if (MyimageView != null) {
MyimageView.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View arg0, MotionEvent event) {
// get pointer index from the event object
// int pointerIndex = event.getActionIndex();
mScaleDetector.onTouchEvent(event);
// get pointer ID
// int pointerId = event.getPointerId(pointerIndex);
// get masked (not specific to a pointer) action
int maskedAction = event.getActionMasked();
switch (maskedAction) {
case MotionEvent.ACTION_DOWN: {
final float x = event.getX();
final float y = event.getY();
mLastTouchX = x;
mLastTouchY = y;
///Toast toast = Toast.makeText(getApplicationContext(), "Action down", Toast.LENGTH_SHORT);
//toast.show();
int pointerIndex = event.getActionIndex();
mActivePointerId = event.getPointerId(0);
TouchMajor = event.getTouchMajor(pointerIndex);
TouchMinor = event.getTouchMinor(pointerIndex);
Pressure = event.getPressure(pointerIndex);
PressureView.setText("Pressure :"+Float.toString(Pressure));
//Orientaation =Double.toString( event.getOrientation(mActivePointerId));
//left Side of scren
if(event.getX(mActivePointerId) < ScreenWidth/2)
{
LeftPixChange = (TouchMajor + TouchMinor) / 2;
LeftPixSize = LeftPixChange;
LeftPixelView.setText(Float.toString(LeftPixSize));
OrientationView.setText("Left Side Clicked");
}
else if(event.getX(mActivePointerId) > ScreenWidth/2)
{
RightPixChange = (TouchMajor + TouchMinor) / 2;
RightPixSize = RightPixChange;
RightPixelView.setText(Float.toString(RightPixSize));
OrientationView.setText("Right Side Clicked");
}
break;
}
case MotionEvent.ACTION_POINTER_DOWN: {
final int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = event.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastTouchX = event.getX(newPointerIndex);
mLastTouchY = event.getY(newPointerIndex);
mActivePointerId = event.getPointerId(newPointerIndex);
}
TouchMajor = event.getTouchMajor(pointerIndex);
TouchMinor = event.getTouchMinor(pointerIndex);
Pressure =Pressure + event.getPressure(pointerIndex);
PressureView.setText("Cummulative pressure :"+Float.toString(Pressure));
//Orientaation = Orientaation+","+ event.getOrientation(mActivePointerId);
// OrientationView.setText(Orientaation);
//we take pointerindex here because pointerId remains same but index will be increased
if(event.getX(pointerIndex) < ScreenWidth/2)
{
LeftPixChange = (TouchMajor + TouchMinor) / 2;
LeftPixSize =LeftPixSize + LeftPixChange;
LeftPixelView.setText(Float.toString(LeftPixSize));
OrientationView.setText("Multi Left side clicked");
IsLeftSideActive = true;
}
else if(event.getX(pointerIndex) > ScreenWidth/2)
{
RightPixChange = (TouchMajor + TouchMinor) / 2;
RightPixSize =RightPixSize + RightPixChange;
RightPixelView.setText(Float.toString(RightPixSize));
OrientationView.setText("Multi Right side clicked");
IsRightSideActive = true;
}
else
{
OrientationView.setText("Both Sidse Clicked simultaneously");
}
break;
}
case MotionEvent.ACTION_MOVE: { // a pointer was moved
// TODO use data
final int pointerIndex = event.findPointerIndex(mActivePointerId);
final float x = event.getX(pointerIndex);
final float y = event.getY(pointerIndex);
if (!mScaleDetector.isInProgress()) {
final float dx = x - mLastTouchX;
final float dy = y - mLastTouchY;
mPosX += dx;
mPosY += dy;
MyimageView.invalidate();
}
mLastTouchX = x;
mLastTouchY = y;
break;
}
case MotionEvent.ACTION_UP:{
mActivePointerId = INVALID_POINTER_ID;
//Toast toast = Toast.makeText(getContext(), "Action UP", Toast.LENGTH_SHORT);
//toast.show();
RightPixelView.setText(Float.toString(0.0f));
LeftPixelView.setText(Float.toString(0.0f));
PressureView.setText("Pressure : 0.0");
OrientationView.setText("");
break;
}
case MotionEvent.ACTION_POINTER_UP:{
final int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = event.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastTouchX = event.getX(newPointerIndex);
mLastTouchY = event.getY(newPointerIndex);
mActivePointerId = event.getPointerId(newPointerIndex);
}
if(event.getX(pointerIndex) > ScreenWidth/2)
{
RightPixSize = RightPixSize - RightPixChange;
RightPixelView.setText(Double.toString(RightPixSize));
}
else if(event.getX(pointerIndex) < ScreenWidth/2){
LeftPixSize = LeftPixSize - LeftPixChange;
LeftPixelView.setText(Double.toString(LeftPixSize));
IsRightSideActive = false;
}
Pressure = Pressure - event.getPressure(event.getActionIndex());
PressureView.setText("Pressure :"+ Double.toString(Pressure));
break;
}
case MotionEvent.ACTION_CANCEL: {
// TODO use data
mActivePointerId = INVALID_POINTER_ID;
MyimageView.invalidate();
break;
}
}
MyimageView.invalidate();
return true;
}});
}
答：方法motionEvent.getSize（）应该可以为您提供所需的信息（但准确度可能会因设备的屏幕而异）。从这个区域可以得到像素数。
