私はcanvasアンドロイドで少し混乱していて、誰かが私のためにいくつかのことを明確にすることができるかどうか疑問に思っていました.
現在、View クラス内に次のコードがあります。
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();
}
これは、私が理解しているように、画面に描画するための2つの異なるアプローチの一種です。私の理解では、myBitmap（ユーザーの描画が描かれているもの）があり、これは"addObjectMode"で正常に機能します。ただし、「moveMode」は、ユーザーが描画した家の平面図の周りでズームスクロールなどをピンチできるようにしたい場合です。
現在、オブジェクトをうまく描画できますが、ボタンを押して有効にするmoveModeと、タッチまたはジェスチャーすると描画が消えます。これはおそらくonDraw();のコードが原因であることは承知しています。しかし、キャンバスはまだ私にとって少し謎です。
最終的には、基本的な元に戻す/やり直し機能と、canvas/bitmap後で開くために保存する機能が必要になります。包括的なキャンバス チュートリアルへのアドバイスやリンクを提供できる人はいますか?
onTouchEvent編集：私の方法も含めると便利かもしれません-
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;
}
}