如何在画布中拖动多个图像？我有一个拖动单个图像的代码。我尝试移动多个图像。但这没有用。有什么办法可以做到这一点吗？这是移动一张图像的代码。
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
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;
public class MyImageView extends View {
private static final int INVALID_POINTER_ID = -1;
private Drawable mImage;
private float mPosX;
private float mPosY;
private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
public MyImageView(Context context) {
this(context, null, 0);
mImage = getResources().getDrawable(R.drawable.baby1);
mImage.setBounds(0, 0, mImage.getIntrinsicWidth(), mImage.getIntrinsicHeight());
}
public MyImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
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: {
final float x = ev.getX();
final float y = ev.getY();
mLastTouchX = x;
mLastTouchY = y;
mActivePointerId = ev.getPointerId(0);
break;
}
case MotionEvent.ACTION_MOVE: {
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(pointerIndex);
final float y = ev.getY(pointerIndex);
// Only move if the ScaleGestureDetector isn't processing a gesture.
if (!mScaleDetector.isInProgress()) {
final float dx = x - mLastTouchX;
final float dy = y - mLastTouchY;
mPosX += dx;
mPosY += dy;
invalidate();
}
mLastTouchX = x;
mLastTouchY = y;
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) {
// 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) {
super.onDraw(canvas);
canvas.save();
Log.d("DEBUG", "X: "+mPosX+" Y: "+mPosY);
canvas.translate(mPosX, mPosY);
canvas.scale(mScaleFactor, mScaleFactor);
mImage.draw(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;
}
}
}
也许存储要拖动的多个视图的 X Y 坐标并覆盖 onTouch 并检查 xy 坐标是否在任何图像视图内（此代码可以在 java、cpp 等的 geeksforgeeks 网站上找到），如果没有则不要不做任何其他事情，更新视图的坐标，使用单选视图中的代码将视图“拖动”到新坐标。唯一的额外步骤是使用图像视图的 xy 坐标检查触摸事件是否在“内部” ' 的景色
或者检查Android在画布上拖动两个图像，它提供了一个处理所有图像的库
要使用此代码片段，只需添加到您的布局 xml 文件中：
<com.m039.study.widgets.MultiTouch
android:layout_width = "match_parent"
android:layout_height = "match_parent"
/>
这个片段只是在视图上的每个手指上画圆圈：
package com.m039.study.widgets;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.MotionEvent;
import android.view.GestureDetector;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Color;
import java.util.Stack;
public class MultiTouch extends View {
private static final String TAG = "m039";
public MultiTouch(Context c) {
super(c);
}
public MultiTouch(Context context, AttributeSet attrs) {
super(context, attrs);
}
static class Point {
public float x;
public float y;
public int pid = -1;
public boolean isOk = false;
}
Paint mPaintCircle = new Paint();
Paint mPaintText = new Paint();
Stack<Point> mPoints = new Stack<Point>();
{
mPaintCircle.setColor(Color.GREEN);
mPaintText.setColor(Color.RED);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (Point point : mPoints) {
if (point.isOk) {
canvas.drawCircle(point.x, point.y, 50, mPaintCircle);
canvas.drawText(Integer.toString(point.pid), point.x, point.y + 50, mPaintText);
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getActionMasked();
int pid = (event.getAction() & event.ACTION_POINTER_ID_MASK) >> event.ACTION_POINTER_ID_SHIFT;
int index = (event.getAction() & event.ACTION_POINTER_INDEX_MASK) >> event.ACTION_POINTER_INDEX_SHIFT;
switch (action) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_POINTER_DOWN:
Point point = new Point();
point.isOk = true;
point.pid = pid;
point.x = event.getX(index);
point.y = event.getY(index);
mPoints.push(point);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
for (Point p: mPoints) {
int pindex = event.findPointerIndex(p.pid);
if (pindex != -1) {
p.x = event.getX(pindex);
p.y = event.getY(pindex);
}
}
invalidate();
break;
case MotionEvent.ACTION_POINTER_UP:
if (mPoints.size() >= 1) {
mPoints.pop();
}
invalidate();
break;
case MotionEvent.ACTION_UP:
default:
mPoints.clear();
invalidate();
break;
}
return true;
}
}