【发布时间】：2012-08-23 14:08:43
【问题描述】：
我为 ImageView 创建了一个缩放和平移类。
我正在尝试创建的功能。 - 它平移单指触摸和移动 - 它可以缩放和平移两根手指的触摸和移动
在大多数情况下，这非常有效。 当我执行以下操作时，它有一个小错误： - 我用一根手指平移（状态：没问题） - 我放下第二根手指，缩放和平移（状态：没问题） - 我松开我的第二根手指（状态：图像跳跃一点）
希望有人能帮我解决这个问题。
我认为它必须与“case MotionEvent.ACTION_POINTER_UP”中的 mLastTouchX 和 mLastTouchY 重置有关
任何帮助将不胜感激！
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;
public class MyImageView extends ImageView {
private static final int INVALID_POINTER_ID = -1;
private float mPosX;
private float mPosY;
private float mLastTouchX;
private float mLastTouchY;
private float mLastGestureX;
private float mLastGestureY;
private int mActivePointerId = INVALID_POINTER_ID;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
public MyImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
}
public MyImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
// Let the ScaleGestureDetector inspect all events.
mScaleDetector.onTouchEvent(ev);
final int action = ev.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
if (!mScaleDetector.isInProgress()) {
final float x = ev.getX();
final float y = ev.getY();
mLastTouchX = x;
mLastTouchY = y;
mActivePointerId = ev.getPointerId(0);
}
break;
}
case MotionEvent.ACTION_POINTER_1_DOWN: {
if (mScaleDetector.isInProgress()) {
final float gx = mScaleDetector.getFocusX();
final float gy = mScaleDetector.getFocusY();
mLastGestureX = gx;
mLastGestureY = gy;
}
break;
}
case MotionEvent.ACTION_MOVE: {
// Only move if the ScaleGestureDetector isn't processing a gesture.
if (!mScaleDetector.isInProgress()) {
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(pointerIndex);
final float y = ev.getY(pointerIndex);
final float dx = x - mLastTouchX;
final float dy = y - mLastTouchY;
mPosX += dx;
mPosY += dy;
invalidate();
mLastTouchX = x;
mLastTouchY = y;
}
else{
final float gx = mScaleDetector.getFocusX();
final float gy = mScaleDetector.getFocusY();
final float gdx = gx - mLastGestureX;
final float gdy = gy - mLastGestureY;
mPosX += gdx;
mPosY += gdy;
invalidate();
mLastGestureX = gx;
mLastGestureY = gy;
}
break;
}
case MotionEvent.ACTION_UP: {
mActivePointerId = INVALID_POINTER_ID;
break;
}
case MotionEvent.ACTION_CANCEL: {
mActivePointerId = INVALID_POINTER_ID;
break;
}
case MotionEvent.ACTION_POINTER_UP: {
final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
Log.d("DEBUG", "mActivePointerId");
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastTouchX = ev.getX(newPointerIndex);
mLastTouchY = ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
}
break;
}
}
return true;
}
@Override
public void onDraw(Canvas canvas) {
canvas.save();
canvas.translate(mPosX, mPosY);
if (mScaleDetector.isInProgress()) {
canvas.scale(mScaleFactor, mScaleFactor, mScaleDetector.getFocusX(), mScaleDetector.getFocusY());
}
else{
canvas.scale(mScaleFactor, mScaleFactor);
}
super.onDraw(canvas);
canvas.restore();
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor();
// Don't let the object get too small or too large.
mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));
invalidate();
return true;
}
}
}
【问题讨论】：
-
嗯。尝试了您的代码并用小图像观察，然后我用第二根手指将图像“跳转”到它。是你提到的错误吗？
-
是的，跳跃就是我要解决的问题。
-
看起来是因为使用了焦点坐标。今天稍后将尝试调试代码。
-
顺便说一句，然后你放第二根手指的预期行为是什么？似乎缩放图像应该放在手指之间。
-
当两根手指放下时，它会缩放图像，但它也会同时使用两根手指的中点进行平移。
标签： android imageview zooming pinch pan