Question

我有问题！我加载了一个大图像（1600x1200），当应用程序启动时，视图就是左上角。我想在它开始时显示中心或其他位置。或者如果我给出了某些坐标并从这一点开始查看会更好。你有什么想法吗？

提前致谢！

Answer 1

您没有向我们展示任何代码，因此我们不了解您的布局或限制，但假设整个屏幕上有ImageView;解决此问题的一种方法是让ScrollView与ImageView - 孩子在一起。然后，您可以使用ScrollView - 方法scrollTo(int x, int y)滚动到任意位置。

在此处阅读更多内容：http://developer.android.com/reference/android/widget/ScrollView.html

Answer 2

我的代码是：

public Scroll(Context context, AttributeSet attrs) {
    super(context, attrs);
    mScroller = new Scroller(context);
    mGestureDetector = new GestureDetector(this);
    mScale = 1;
    mZoomController = new ZoomButtonsController(this);
    mZoomController.setAutoDismissed(true);
    mZoomController.setOnZoomListener(this);
    mZoomController.setZoomSpeed(25);
    mZoomController.setZoomInEnabled(mScale < MAX_ZOOM);
    mZoomController.setZoomOutEnabled(mScale > MIN_ZOOM);
    makeZoomLabel(context, mZoomController);

    mZoomFormat = NumberFormat.getPercentInstance();
    mZoomLabel.setText("Zoom: " + mZoomFormat.format(mScale));

    mPicture = makeContent();

    setVerticalScrollBarEnabled(true);
    setHorizontalScrollBarEnabled(true);
    TypedArray a = context.obtainStyledAttributes(R.styleable.Scroll);
    initializeScrollbars(a);
    a.recycle();
    mMatrix = new Matrix();
    mDst = new float[2];
}

public Scroll(Context context) {
    this(context, null);
}

@Override
protected void onDetachedFromWindow() {
    super.onDetachedFromWindow();
    mZoomController.setVisible(false);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    return mGestureDetector.onTouchEvent(event);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.save();
    if (mScroller.computeScrollOffset()) {
        mX = mScroller.getCurrX();
        mY = mScroller.getCurrY();
        invalidate();
    }

    mMatrix.reset();
    mMatrix.preTranslate(mX * mScale, mY * mScale);

    int w = getWidth();
    int h = getHeight();
    float pivotX = Math.max(Math.min(-mX, w / 2), 2 * w - WIDTH - mX);
    float pivotY = Math.max(Math.min(-mY, h / 2), 2 * h - HEIGHT - mY);
    mMatrix.preScale(mScale, mScale, pivotX, pivotY);
    canvas.concat(mMatrix);

    // draw content
    mPicture.draw(canvas);
    canvas.restore();
}

@Override
protected int computeHorizontalScrollExtent() {
    return Math.round(computeHorizontalScrollRange() * getWidth() / (WIDTH * mScale));
}
@Override
protected int computeHorizontalScrollOffset() {
    mMatrix.mapPoints(mDst, SRC);
    float x = -mDst[0] / mScale;
    return Math.round(computeHorizontalScrollRange() * x / WIDTH);
}
@Override
protected int computeVerticalScrollExtent() {
    return Math.round(computeVerticalScrollRange() * getHeight() / (HEIGHT * mScale));
}
@Override
protected int computeVerticalScrollOffset() {
    mMatrix.mapPoints(mDst, SRC);
    float y = -mDst[1] / mScale;
    return Math.round(computeVerticalScrollRange() * y / HEIGHT);
}

public boolean onDown(MotionEvent e) {
    mZoomController.setVisible(false);
    return true;
}

public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    int minX = (int) (getWidth() - WIDTH);
    int minY = (int) (getHeight() - HEIGHT);
    mScroller.fling((int) mX, (int) mY, (int) velocityX, (int) velocityY, minX, 0, minY, 0);
    invalidate();
    return true;
}

public void onLongPress(MotionEvent e) {
    mZoomController.setVisible(true);
}

public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
    mX -= distanceX / mScale;
    mY -= distanceY / mScale;
    mX = Math.max(getWidth() - WIDTH, Math.min(0, mX));
    mY = Math.max(getHeight() - HEIGHT, Math.min(0, mY));
    invalidate();
    return true;
}

public void onShowPress(MotionEvent e) {
}

public boolean onSingleTapUp(MotionEvent e) {
    return false;
}

public void onVisibilityChanged(boolean visible) {
}

public void onZoom(boolean zoomIn) {
    mScale += zoomIn? 0.1 : -0.1;
    mScale = Math.min(MAX_ZOOM, Math.max(MIN_ZOOM, mScale));
    mZoomLabel.setText("Zoom: " + mZoomFormat.format(mScale));
    invalidate();

    mZoomController.setZoomInEnabled(mScale != MAX_ZOOM);
    mZoomController.setZoomOutEnabled(mScale != MIN_ZOOM);
}

private void makeZoomLabel(Context context, ZoomButtonsController zoomController) {
    ViewGroup container = zoomController.getContainer();
    View controls = zoomController.getZoomControls();
    LayoutParams p0 = controls.getLayoutParams();
    container.removeView(controls);
    LinearLayout layout = new LinearLayout(context);
    layout.setOrientation(LinearLayout.VERTICAL);
    mZoomLabel = new TextView(context);
    mZoomLabel.setPadding(12, 0, 12, 0);
    mZoomLabel.setTypeface(Typeface.DEFAULT_BOLD);
    mZoomLabel.setTextColor(0xff000000);
    PaintDrawable d = new PaintDrawable(0xeeffffff);
    d.setCornerRadius(6);
    mZoomLabel.setBackgroundDrawable(d);
    mZoomLabel.setTextSize(20);
    mZoomLabel.setGravity(Gravity.CENTER_HORIZONTAL);
    LinearLayout.LayoutParams p1 = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    p1.gravity = Gravity.CENTER_HORIZONTAL;
    layout.addView(mZoomLabel, p1);
    layout.addView(controls);
    container.addView(layout, p0);
}

private Picture makeContent() {
    Picture picture = new Picture();


    Canvas c = picture.beginRecording(WIDTH, HEIGHT);

    //draw something

    picture.endRecording();
    return picture;
}

}

从特定位置开始查看图像

2 个答案: