如何将文本添加到浮动操作按钮？

Question

我想在浮动操作按钮而不是图像上显示文本。我尝试使用android：contentDescription =“string”但操作按钮似乎是空的我需要设置一些颜色或做任何其他事情。请让我知道。

Answer 1

In our project we are using a custom class called TextDrawable. This class extends Drawable and in its method draw(Canvas) it simple draws the text on canvas. The class is suitable for our specific needs but I think, the idea (mainly in draw() method will help you:

public class TextDrawable extends Drawable {

protected final Paint textPaint;
protected ColorStateList color;
protected String text;
protected int iHeight;
protected int iWidth;
protected int measuredWidth, measuredHeight;
private float ascent;
/**
 * A flag whether the drawable is stateful - whether to redraw if the state of view has changed
 */
protected boolean stateful;
/**
 * Vertical alignment of text
 */
private VerticalAlignment verticalAlignment;

.... some constructors...
public TextDrawable(Context ctx, String text, ColorStateList color, float textSize, VerticalAlignment verticalAlignment) {
    textPaint = new Paint();
    this.text = text;
    initPaint();
    this.textPaint.setTextSize(textSize);
    measureSize();
    setBounds(0, 0, iWidth, iHeight);
    this.color = color;
    textPaint.setColor(color.getDefaultColor());
    this.verticalAlignment = verticalAlignment;
}

/**
 * Set bounds of drawable to start on coordinate [0,0] and end on coordinate[measuredWidth,
 * measuredHeight]
 */
public final void setBoundsByMeasuredSize() {
    setBounds(0, 0, measuredWidth, measuredHeight);
    invalidateSelf();
}

@Override
public boolean isStateful() {
    return stateful;
}

public void setStateful(boolean stateful) {
    this.stateful = stateful;
}

private void initPaint() {
    textPaint.setAntiAlias(true);
    textPaint.setTextAlign(Paint.Align.CENTER);
}

/**
 * Vertical alignment of text within the drawable (Horizontally it is always aligned to center
 */
public VerticalAlignment getVerticalAlignment() {
    return verticalAlignment;
}

/**
 * Vertical alignment of text within the drawable (Horizontally it is always aligned to center
 */
public void setVerticalAlignment(VerticalAlignment verticalAlignment) {
    if (this.verticalAlignment != verticalAlignment) {
        this.verticalAlignment = verticalAlignment;
        invalidateSelf();
    }
}

/**
 * Displayed text
 */
public String getText() {
    return text;
}

/**
 * Displayed text
 */

public void setText(String text) {
    if (this.text == null || !this.text.equals(text)) {
        this.text = text;
        invalidateSelf();
    }
}

/**
 * The color of text
 */
public ColorStateList getColor() {
    return color;
}

/**
 * The color of text
 */
public void setColor(ColorStateList colorStateList) {
    if (this.color == null || !this.color.equals(colorStateList)) {
        this.color = colorStateList;
        invalidateSelf();
    }
}

/**
 * The color of text
 */
public void setColor(int color) {
    setColor(ColorStateList.valueOf(color));
}

/**
 * Text size
 */
public void setTextSize(float size) {
    if (this.textPaint.getTextSize() != size) {
        this.textPaint.setTextSize(size);
        measureSize();
        invalidateSelf();
    }
}

/**
 * Text size
 */
public void setTextSize(int unit, float size, Context context) {
    setTextSize(TypedValue.applyDimension(unit, size, context.getResources().getDisplayMetrics()));
}

/**
 * This method is called by default when any property that may have some influence on the size
 * of drawable This method should use measuredWidth and measuredHeight properties to store the
 * measured walues By default the measuredWIdth and measuredHeight are set to iWidth and iHeight
 * (size of text) by this method.
 */
protected void measureSize() {
    ascent = -textPaint.ascent();
    iWidth = (int) (0.5f + textPaint.measureText(text));
    iHeight = (int) (0.5f + textPaint.descent() + ascent);
    measuredWidth = iWidth;
    measuredHeight = iHeight;
}

public float getTextSize() {
    return textPaint.getTextSize();
}

@Override
protected boolean onStateChange(int[] state) {
    int clr = color != null ? color.getColorForState(state, 0) : 0;
    if (textPaint.getColor() != clr) {
        textPaint.setColor(clr);
        return true;
    } else {
        return false;
    }
}

public Typeface getTypeface() {
    return textPaint.getTypeface();
}

public void setTypeface(Typeface typeface) {
    if (!textPaint.getTypeface().equals(typeface)) {
        textPaint.setTypeface(typeface);
        invalidateSelf();
    }
}

/**
 * The method is called before the text is drawn. This method can be overridden to draw some background (by default this method does nothing).
 * @param canvas The canvas where to draw.
 * @param bounds The bounds of the drawable.
 */
protected void drawBefore(Canvas canvas, Rect bounds) {

}

/**
 * The method is called after the text is drawn. This method can be overriden to draw some more graphics over the text (by default this method does nothing).
 * @param canvas The canvas where to draw.
 * @param bounds The bound of the drawable.
 */
protected void drawAfter(Canvas canvas, Rect bounds) {

}

@Override
public void draw(Canvas canvas) {
    if (text == null || text.isEmpty()) {
        return;
    }
    final Rect bounds = getBounds();
    int stack = canvas.save();
    canvas.translate(bounds.left, bounds.top);
    drawBefore(canvas, bounds);
    if (text != null && !text.isEmpty()) {
        final float x = bounds.width() >= iWidth ? bounds.centerX() : iWidth * 0.5f;
        float y = 0;
        switch (verticalAlignment) {
            case BASELINE:
                y = (bounds.height() - iHeight) * 0.5f + ascent;
                break;
            case TOP:
                y = bounds.height();
                break;
            case BOTTOM:
                y = bounds.height();
                break;
        }
        canvas.drawText(text, x, y, textPaint);
    }
    drawAfter(canvas, bounds);
    canvas.restoreToCount(stack);

}

@Override
public void setAlpha(int alpha) {
    if (textPaint.getAlpha() != alpha) {
        textPaint.setAlpha(alpha);
        invalidateSelf();
    }
}

@Override
public void setColorFilter(ColorFilter cf) {
    if (textPaint.getColorFilter() == null || !textPaint.getColorFilter().equals(cf)) {
        textPaint.setColorFilter(cf);
        invalidateSelf();
    }
}

@Override
public int getOpacity() {
    return PixelFormat.TRANSLUCENT;
}

public enum VerticalAlignment {
    TOP, BOTTOM, BASELINE
}

and how to use it:

fab.setImageDrawable(new TextDrawable(fab.getContext(), "FAB", ColorStateList.valueOf(Color.BLACK), 32.f, VerticalAlignment.BASELINE));

(fab is FloatingActionButton)