How to outline a TextView?

问题:

What I want to do? (blue will be changed as white)

What I did?
I have found a class which extends TextView that able to outline textview very close to what I want. The problem is that I could not change stroke color to any color, it draws always as black. How to set border color as white?

What is my output:

Where are my codes?

public class TypeFaceTextView extends TextView {

private static Paint getWhiteBorderPaint(){
    Paint p = new Paint(Color.WHITE);
    return p;
}

private static final Paint BLACK_BORDER_PAINT = getWhiteBorderPaint();

static {
    BLACK_BORDER_PAINT.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
}

@Override
public void setText(CharSequence text, BufferType type) {

    super.setText(String.format(text.toString()), type);
}

private static final int BORDER_WIDTH = 1;

private Typeface typeface;

public TypeFaceTextView(Context context) {
    super(context);
}

public TypeFaceTextView(Context context, AttributeSet attrs) {
    super(context, attrs);

    setDrawingCacheEnabled(false);

    setTypeface(attrs);
}

private void setTypeface(AttributeSet attrs) {
    final String typefaceFileName = attrs.getAttributeValue(null, "typeface");
    if (typefaceFileName != null) {
        typeface = Typeface.createFromAsset(getContext().getAssets(), typefaceFileName);
    }

    setTypeface(typeface);
}

public TypeFaceTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    setTypeface(attrs);
}

@Override
public void draw(Canvas aCanvas) {
    aCanvas.saveLayer(null, BLACK_BORDER_PAINT, Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
            | Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.MATRIX_SAVE_FLAG);

    drawBackground(aCanvas, -BORDER_WIDTH, -BORDER_WIDTH);
    drawBackground(aCanvas, BORDER_WIDTH + BORDER_WIDTH, 0);
    drawBackground(aCanvas, 0, BORDER_WIDTH + BORDER_WIDTH);
    drawBackground(aCanvas, -BORDER_WIDTH - BORDER_WIDTH, 0);

    aCanvas.restore();
    super.draw(aCanvas);

}

private void drawBackground(Canvas aCanvas, int aDX, int aDY) {
    aCanvas.translate(aDX, aDY);
    super.draw(aCanvas);
}
}

回答1:

1) create your textview object extends TextView

public class YourTextView extends TextView { .........

2) Do this on its draw method

@Override
public void draw(Canvas canvas) {
        for (int i = 0; i < 5; i++) {
        super.draw(canvas);
    }
}

3) set textview's xml side as below

android:shadowColor="@color/white"
android:shadowRadius="5"

回答2:

Couldn't this this but try experimenting with: PorterDuff.Mode

http://developer.android.com/reference/android/graphics/PorterDuff.Mode.html

Try changing it to 'ADD' or 'CLEAR', hope this helps.

回答3:

You need to change your getWhiteBorderPaint() method to the following:

private static Paint getWhiteBorderPaint(){
    Paint p = new Paint();
    p.setColor(Color.WHITE);
    return p;
}

The Paint constructor only takes bitmasked flags and doesn't support arbitrary ints as parameters.

回答4:

Investigated into the original problem stated by this question. Found the solution.

First, change DST_OUT to DARKEN

static {
    BLACK_BORDER_PAINT.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DARKEN));
}

Secondly, save the original text color, and put the intended outline color up, draw the outline, and then restore the original text color.

@Override
public void draw(Canvas aCanvas) {
    int originalColor = this.getCurrentTextColor();
    this.setTextColor(0xff000000); //set it to white.

    aCanvas.saveLayer(null, borderPaint, Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
            | Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.MATRIX_SAVE_FLAG);

        drawBackground(aCanvas, -BORDER_WIDTH, -BORDER_WIDTH);
        drawBackground(aCanvas, BORDER_WIDTH + BORDER_WIDTH, 0);
        drawBackground(aCanvas, 0, BORDER_WIDTH + BORDER_WIDTH);
        drawBackground(aCanvas, -BORDER_WIDTH - BORDER_WIDTH, 0);

    this.setTextColor(originalColor);
    aCanvas.restore();
    super.draw(aCanvas);
}

回答5:

I found simple way to outline view without inheritance from TextView. I had wrote simple library that use Android's Spannable for outlining text. This solution gives possibility to outline only part of text.

Library: OutlineSpan

Class (you can copy only class):OutlineSpan