2
我在Android中与canvas有点混淆，并想知道是否有人可以为我澄清一些事情。Android - 画布混乱（绘图和滚动）
目前，我有这个代码我的视图类：
class HomerView extends View { // the custom View for drawing on
// set up Bitmap, canvas, path and paint
private Bitmap myBitmap; // the initial image we turn into our canvas
private Canvas myCanvas; // the canvas we are drawing on
private Rect myRect; // the mathematical path of the lines we draw
private Paint myBitmapPaint; // the paint we use to draw the bitmap
// get the width of the entire tablet screen
private int screenWidth = getContext().getResources()
.getDisplayMetrics().widthPixels;
// get the height of the entire tablet screen
private int screenHeight = getContext().getResources()
.getDisplayMetrics().heightPixels;
private int mX, mY, iX, iY; // current x,y and initial x,y
private static final float TOUCH_TOLERANCE = 4;
private static final int INVALID_POINTER_ID = -1;
private float mPosX;
private float mPosY;
private BitmapDrawable mImage;
private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
public HomerView(Context context) { // constructor of HomerView
super(context);
myBitmap = Bitmap.createBitmap(screenWidth, screenHeight,
Bitmap.Config.ARGB_8888); // set our drawable space - the bitmap which becomes the canvas we draw on
myCanvas = new Canvas(myBitmap); // set our canvas to our bitmap which we just set up
myRect = new Rect(); // make a new rect
myBitmapPaint = new Paint(Paint.DITHER_FLAG); // set dither to ON in our saved drawing - gives better color interaction
setHorizontalScrollBarEnabled(true);
setVerticalScrollBarEnabled(true);
TypedArray a = context.obtainStyledAttributes(R.styleable.View);
initializeScrollbars(a);
a.recycle();
computeVerticalScrollRange();
computeHorizontalScrollRange();
mImage = new BitmapDrawable(getResources(), myBitmap);
mScaleDetector = new ScaleGestureDetector(context,
new ScaleListener());
}
public HomerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mScaleDetector = new ScaleGestureDetector(context,
new ScaleListener());
}
public HomerView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
protected void onDraw(Canvas canvas) { // method used when we want to draw something to our canvas
super.onDraw(canvas);
if (addObjectMode == true) {
canvas.drawColor(Color.TRANSPARENT); // sets canvas colour
canvas.drawBitmap(myBitmap, 0, 0, myBitmapPaint); // save the canvas to bitmap - the numbers are the x, y coords we are drawing from
canvas.drawRect(myRect, myPaint); // draw the rectangle that the user has drawn using the paint we set up
} else if (moveMode == true) {
canvas.save();
System.out.println("X: " + mPosX + " Y: " + mPosY);
canvas.translate(mPosX, mPosY);
canvas.scale(mScaleFactor, mScaleFactor);
mImage.draw(canvas);
canvas.restore();
}
这是种2种不同的方法来绘制到屏幕我所理解的合并的。我的理解是，我有myBitmap（这是用户图纸绘制的），并且这适用于“addObjectMode”。但是，“moveMode”是我希望用户能够在他们绘制的房屋计划周围捏缩放滚动等。
目前，我可以很好地绘制物体，但是当我按下按钮启用moveMode时，绘图在我触摸或手势时消失。我知道这可能是因为onDraw()中的代码;但画布对我来说仍然有点神秘。
最后，我想要一个基本的撤销/重做功能，以及保存canvas/bitmap以后打开。任何人都可以提供任何建议或链接到任何全面的画布教程？
编辑：这可能是有用的，包括我的onTouchEvent方法too-
public boolean onTouchEvent(MotionEvent event) { // on any touch event
if (addObjectMode == true) {
float x = event.getX(); // get current X
float y = event.getY(); // get current Y
switch (event.getAction()) { // what action is the user performing?
case MotionEvent.ACTION_DOWN: // if user is touching down
touch_Start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE: // if user is moving finger while touched down
touch_Move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP: // if user has released finger
touch_Up();
invalidate();
break;
}
return true;
} else if (moveMode == true) {
mScaleDetector.onTouchEvent(event);
final int action = event.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
final float x = event.getX();
final float y = event.getY();
mLastTouchX = x;
mLastTouchY = y;
mActivePointerId = event.getPointerId(0);
break;
}
case MotionEvent.ACTION_MOVE: {
final int pointerIndex = event
.findPointerIndex(mActivePointerId);
final float x = event.getX(pointerIndex);
final float y = event.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 = (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);
}
break;
}
}
return true;
} else {
return false;
}
}
嗯......不行'mImage.draw（canvas）;'draw to canvas？我做了什么，而不是添加'\t \t \t \t canvas.drawBitmap（MYBITMAP，0，0，myBitmapPaint）;'canvas.restore前（）;虽然当我捏缩放并切换到“绘图模式”时，它立即恢复到初始缩放级别，就好像没有发生滚动一样。任何想法为什么？ – 2013-02-27 17:28:55
是，以同样的方式您的绘图并没有适用于您的movemode，你的翻译转换没有被应用到您的drawMode这里;） – Guian 2013-02-27 17:31:32
我建议你分开移动/从绘制方法来绘制mecanism出来，设法绘制在用户事件的唯一输出位图。那么onDraw方法只绘制输出位图。 – Guian 2013-02-27 17:34:12