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。但它没有用。有没有办法做到这一点？这是移动一个图像的代码..提前感谢

 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

如果您不介意我只发布我的代码段，也许它可以帮助您找出问题所在。

要使用此代码段，只需添加布局xml文件：

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

此代码段只是在视图上的每个手指上绘制圆圈：

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;
    }
}

P.S。请告诉我它是否有用。

通过触摸android在画布中拖动多个图像

1 个答案: