在画布中拖动多个图像通过触摸Android

Question

如何在画布中拖动多个图像？我有一个代码来拖动单个图像。我试图移动多个图像。但它没有奏效。有没有办法做到这一点？这是一个移动图像的代码..提前

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; 
    } 
} 

} 

Answer 1

谢谢如果你不介意，我只是发表我的代码片段，也许它会帮助你找出问题。

要使用这个片段只是在你的布局XML文件中加入：

<com.m039.study.widgets.MultiTouch 
    android:layout_width = "match_parent" 
    android:layout_height = "match_parent" 
    /> 

这个片段只是画出圆圈上视图中的每个手指：

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; 
    } 
} 

附：请告诉我它是否有帮助。