Canvas.drawTextOnPath(…) not working on Lollipop

问题:

canvas.DrawTextOnPath does not seem to work on a Lollipop device. See the difference here. (The Nexus 10 image is correct but Lollipop does not display correctly)

The code is a simple path draw.

// Path for the inner circle
unitPath = new Path();
unitPath.addArc(unitRect, 180.0f, 180.0f);

// Draw the text and the path
canvas.drawTextOnPath("Inner Circle", unitPath, 0.0f, 0.0f, unitPaint);
canvas.drawPath(unitPath,unitPaint);

The Android Studio test project illustrating this issue can be seen here for anyone who wants to see it. https://dl.dropboxusercontent.com/u/6768304/WebLinks/TestApp.rar

Is there something "different" I need to do on this device?

回答1:

OK so it seems that DrawTextOnPath is a little broken now with font sizes below 1.0f

The solution is to scale everything up, draw the text then shrink it back down.

The drawTitle method in the demo project would change from this:

private void drawTitle(Canvas canvas) {
    canvas.drawTextOnPath(upperTitle, upperTitlePath, 0.0f, 0.02f, unitPaint);
    canvas.drawTextOnPath(lowerTitle, lowerTitlePath, 0.0f, 0.0f, unitPaint);
    canvas.drawTextOnPath(unitTitle, unitPath, 0.0f, 0.0f, unitPaint);
    canvas.drawPath(unitPath,unitPaint);
}

to this:

private void drawTitle(Canvas canvas) {
    //Save original font size
    float originalTextSize = unitPaint.getTextSize();

    // set a magnification factor
    final float magnifier = 100f;

    // Scale the canvas
    canvas.save();
    canvas.scale(1f / magnifier, 1f / magnifier);

    // create new rects and paths based on the new scale
    unitRect = new RectF();
    unitRect.set((faceRect.left + unitPosition) * magnifier, (faceRect.top + unitPosition) * magnifier, (faceRect.right - unitPosition) * magnifier, (faceRect.bottom - unitPosition) * magnifier);
    unitPath = new Path();
    unitPath.addArc(unitRect, 180.0f, 180.0f);

    titleRect = new RectF();
    titleRect.set((faceRect.left + titlePosition) * magnifier, (faceRect.top + titlePosition) * magnifier, (faceRect.right - titlePosition) * magnifier, (faceRect.bottom - titlePosition) * magnifier);
    upperTitlePath = new Path();
    upperTitlePath.addArc(titleRect, 180.0f, 180.0f);

    titleRect = new RectF();
    titleRect.set((faceRect.left + titlePosition) * magnifier, (faceRect.top + titlePosition) * magnifier, (faceRect.right - titlePosition) * magnifier, (faceRect.bottom - titlePosition) * magnifier);
    lowerTitlePath = new Path();
    lowerTitlePath.addArc(titleRect, -180.0f, -180.0f);

    // increase the font size
    unitPaint.setTextSize(originalTextSize * magnifier);

    // do the drawing of the text
    canvas.drawTextOnPath(unitTitle, unitPath, 0.0f, 0.0f, unitPaint);
    canvas.drawTextOnPath(upperTitle, upperTitlePath, 0.0f, 0.02f, unitPaint);
    canvas.drawTextOnPath(lowerTitle, lowerTitlePath, 0.0f, 0.0f, unitPaint);

    // bring everything back to normal
    canvas.restore();
    unitPaint.setTextSize(originalTextSize);

    canvas.drawPath(unitPath, unitPaint);
}

回答2:

Yes, broken as of Lollipop. Worked perfectly in 4.4.4.

https://code.google.com/p/android/issues/detail?id=40965

I'm setting text size to 5.f if it was smaller, scaling the canvas down, and scaling the baseline path up appropriately. Slow but it works, can't wait till I can remove this awful cludge.