如何在TextView的扩展类中正确绘制文本？

发布于 2024-10-05 18:45:29 字数 3165 浏览 10 评论 0原文

我目前正在扩展 TextView，在文本周围添加轮廓。到目前为止，我遇到的唯一问题是我无法将“轮廓”正确地放置在文本后面。如果我对扩展类进行编码，如下所示，我会得到一个如下所示的标签：

注意：在上面屏幕截图，我将填充颜色设置为白色，描边颜色设置为黑色。

我做错了什么？

public class OutlinedTextView extends TextView {
    /* ===========================================================
     * Constants
     * =========================================================== */
    private static final float OUTLINE_PROPORTION = 0.1f;

    /* ===========================================================
     * Members
     * =========================================================== */
    private final Paint mStrokePaint = new Paint();
    private int mOutlineColor = Color.TRANSPARENT;

    /* ===========================================================
     * Constructors
     * =========================================================== */
    public OutlinedTextView(Context context) {
        super(context);
        this.setupPaint();
    }
    public OutlinedTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }
    public OutlinedTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }

    /* ===========================================================
     * Overrides
     * =========================================================== */
    @Override
    protected void onDraw(Canvas canvas) {
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * OUTLINE_PROPORTION);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // Figure out the drawing coordinates
        //mStrokePaint.getTextBounds(text, 0, text.length(), mTextBounds);

        // draw everything
        canvas.drawText(text,
                super.getWidth() * 0.5f, super.getBottom() * 0.5f,
                mStrokePaint);
        super.onDraw(canvas);
    }

    /* ===========================================================
     * Private/Protected Methods
     * =========================================================== */
    private final void setupPaint() {
        mStrokePaint.setAntiAlias(true);
        mStrokePaint.setStyle(Paint.Style.STROKE);
        mStrokePaint.setTextAlign(Paint.Align.CENTER);
    }
    private final void setupAttributes(Context context, AttributeSet attrs) {
        final TypedArray array = context.obtainStyledAttributes(attrs,
                R.styleable.OutlinedTextView);
        mOutlineColor = array.getColor(
                R.styleable.OutlinedTextView_outlineColor, 0x00000000);
        array.recycle(); 

        // Force this text label to be centered
        super.setGravity(Gravity.CENTER_HORIZONTAL);
    }
}

原文

I'm currently working on extending a TextView, adding an outline around the text. Thus far, the only problem I've been having is my inability to position the "outline" correctly behind a text. If I code the extended class like the one portrayed below, I get a label that looks like this:

Note: in the above screenshot, I set the fill color to white, and the stroke color to black.

What am I doing wrong?

public class OutlinedTextView extends TextView {
    /* ===========================================================
     * Constants
     * =========================================================== */
    private static final float OUTLINE_PROPORTION = 0.1f;

    /* ===========================================================
     * Members
     * =========================================================== */
    private final Paint mStrokePaint = new Paint();
    private int mOutlineColor = Color.TRANSPARENT;

    /* ===========================================================
     * Constructors
     * =========================================================== */
    public OutlinedTextView(Context context) {
        super(context);
        this.setupPaint();
    }
    public OutlinedTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }
    public OutlinedTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }

    /* ===========================================================
     * Overrides
     * =========================================================== */
    @Override
    protected void onDraw(Canvas canvas) {
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * OUTLINE_PROPORTION);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // Figure out the drawing coordinates
        //mStrokePaint.getTextBounds(text, 0, text.length(), mTextBounds);

        // draw everything
        canvas.drawText(text,
                super.getWidth() * 0.5f, super.getBottom() * 0.5f,
                mStrokePaint);
        super.onDraw(canvas);
    }

    /* ===========================================================
     * Private/Protected Methods
     * =========================================================== */
    private final void setupPaint() {
        mStrokePaint.setAntiAlias(true);
        mStrokePaint.setStyle(Paint.Style.STROKE);
        mStrokePaint.setTextAlign(Paint.Align.CENTER);
    }
    private final void setupAttributes(Context context, AttributeSet attrs) {
        final TypedArray array = context.obtainStyledAttributes(attrs,
                R.styleable.OutlinedTextView);
        mOutlineColor = array.getColor(
                R.styleable.OutlinedTextView_outlineColor, 0x00000000);
        array.recycle(); 

        // Force this text label to be centered
        super.setGravity(Gravity.CENTER_HORIZONTAL);
    }
}

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梦年海沫深 2024-10-12 18:45:29

呸，我真是太蠢了。我只需要更改注释掉的行：

super.getPaint().getTextBounds(text, 0, text.length(), mTextBounds);

此外，为了实际渲染文本，我需要平均该视图的高度和文本的高度：

// draw everything
canvas.drawText(text,
    super.getWidth() * 0.5f, (super.getHeight() + mTextBounds.height()) * 0.5f,
    mStrokePaint);

整个代码现在如下所示：

public class OutlinedTextView extends TextView {
    /* ===========================================================
     * Constants
     * =========================================================== */
    private static final float OUTLINE_PROPORTION = 0.1f;

    /* ===========================================================
     * Members
     * =========================================================== */
    private final Paint mStrokePaint = new Paint();
    private final Rect mTextBounds = new Rect();
    private int mOutlineColor = Color.TRANSPARENT;

    /* ===========================================================
     * Constructors
     * =========================================================== */
    public OutlinedTextView(Context context) {
        super(context);
        this.setupPaint();
    }
    public OutlinedTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }
    public OutlinedTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }

    /* ===========================================================
     * Overrides
     * =========================================================== */
    @Override
    protected void onDraw(Canvas canvas) {
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * OUTLINE_PROPORTION);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // Figure out the drawing coordinates
        super.getPaint().getTextBounds(text, 0, text.length(), mTextBounds);

        // draw everything
        canvas.drawText(text,
                super.getWidth() * 0.5f, (super.getHeight() + mTextBounds.height()) * 0.5f,
                mStrokePaint);
        super.onDraw(canvas);
    }

    /* ===========================================================
     * Private/Protected Methods
     * =========================================================== */
    private final void setupPaint() {
        mStrokePaint.setAntiAlias(true);
        mStrokePaint.setStyle(Paint.Style.STROKE);
        mStrokePaint.setTextAlign(Paint.Align.CENTER);
    }
    private final void setupAttributes(Context context, AttributeSet attrs) {
        final TypedArray array = context.obtainStyledAttributes(attrs,
                R.styleable.OutlinedTextView);
        mOutlineColor = array.getColor(
                R.styleable.OutlinedTextView_outlineColor, 0x00000000);
        array.recycle(); 

        // Force this text label to be centered
        super.setGravity(Gravity.CENTER_HORIZONTAL);
    }
}

Bah, that was stupid of me. I just needed to change-up that commented-out line:

super.getPaint().getTextBounds(text, 0, text.length(), mTextBounds);

In addition, for actually rendering the text, I need to average this view's height and the text's height:

// draw everything
canvas.drawText(text,
    super.getWidth() * 0.5f, (super.getHeight() + mTextBounds.height()) * 0.5f,
    mStrokePaint);

The entire code now reads as follows:

public class OutlinedTextView extends TextView {
    /* ===========================================================
     * Constants
     * =========================================================== */
    private static final float OUTLINE_PROPORTION = 0.1f;

    /* ===========================================================
     * Members
     * =========================================================== */
    private final Paint mStrokePaint = new Paint();
    private final Rect mTextBounds = new Rect();
    private int mOutlineColor = Color.TRANSPARENT;

    /* ===========================================================
     * Constructors
     * =========================================================== */
    public OutlinedTextView(Context context) {
        super(context);
        this.setupPaint();
    }
    public OutlinedTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }
    public OutlinedTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.setupPaint();
        this.setupAttributes(context, attrs);
    }

    /* ===========================================================
     * Overrides
     * =========================================================== */
    @Override
    protected void onDraw(Canvas canvas) {
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * OUTLINE_PROPORTION);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // Figure out the drawing coordinates
        super.getPaint().getTextBounds(text, 0, text.length(), mTextBounds);

        // draw everything
        canvas.drawText(text,
                super.getWidth() * 0.5f, (super.getHeight() + mTextBounds.height()) * 0.5f,
                mStrokePaint);
        super.onDraw(canvas);
    }

    /* ===========================================================
     * Private/Protected Methods
     * =========================================================== */
    private final void setupPaint() {
        mStrokePaint.setAntiAlias(true);
        mStrokePaint.setStyle(Paint.Style.STROKE);
        mStrokePaint.setTextAlign(Paint.Align.CENTER);
    }
    private final void setupAttributes(Context context, AttributeSet attrs) {
        final TypedArray array = context.obtainStyledAttributes(attrs,
                R.styleable.OutlinedTextView);
        mOutlineColor = array.getColor(
                R.styleable.OutlinedTextView_outlineColor, 0x00000000);
        array.recycle(); 

        // Force this text label to be centered
        super.setGravity(Gravity.CENTER_HORIZONTAL);
    }
}

回复收藏 0 原文

要走就滚别墨迹 2024-10-12 18:45:29

我已经花了一段时间来研究其中的一些示例，因为似乎没有一个是完全正确的，当我最终掌握了文本发生的情况并戴上数学帽子后，我将 onDraw 更改为如下所示，无论文本的大小或它包含的视图的大小和形状如何，它都完美地位于...

@Override
protected void onDraw(Canvas canvas) {
    if (!isInEditMode()){
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * mOutlineSize);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // draw everything
        canvas.drawText(text,
                (this.getWidth()-mStrokePaint.measureText(text))/2, this.getBaseline(),
                mStrokePaint);
    }
    super.onDraw(canvas);
}

事实证明，与使用的许多解决方案相比，数学和矩形计算要少得多。

编辑：忘记提及我在初始化中复制了超级的文本对齐，并且不要强制它居中。此处计算的绘制文本位置始终是描边文本的正确居中位置。

I've been plugging away with some of these examples for a while, as none seemed to line up quite right, and once I finally got a handle on what is happening with text and put my maths hat on I changed my onDraw for this to be the following and it sits perfectly no matter the size of the text or what size and shape it's containing view is...

@Override
protected void onDraw(Canvas canvas) {
    if (!isInEditMode()){
        // Get the text to print
        final float textSize = super.getTextSize();
        final String text = super.getText().toString();

        // setup stroke
        mStrokePaint.setColor(mOutlineColor);
        mStrokePaint.setStrokeWidth(textSize * mOutlineSize);
        mStrokePaint.setTextSize(textSize);
        mStrokePaint.setFlags(super.getPaintFlags());
        mStrokePaint.setTypeface(super.getTypeface());

        // draw everything
        canvas.drawText(text,
                (this.getWidth()-mStrokePaint.measureText(text))/2, this.getBaseline(),
                mStrokePaint);
    }
    super.onDraw(canvas);
}

Turned out to be far less maths and Rect calculating than a lot of solutions used too.

Edit: Forgot to mention that I copy the textalign of the super in the initialisation and DON'T force it to center. The drawText position calculated here is always going to be the properly centered position for the stroked text.

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以往的大感动 2024-10-12 18:45:29

我已经尝试让它工作一段时间了，我有一个解决方案，但它仅适用于特殊情况！可以获取在 TextView 中使用的 Layout 对象来绘制文本。您可以创建该对象的副本并在 onDraw(Canvas) 方法中使用它。

    final Layout originalLayout = super.getLayout();
    final Layout layout = new StaticLayout(text, mStrokePaint,
    originalLayout.getWidth(), originalLayout.getAlignment(),
    originalLayout.getSpacingMultiplier(), originalLayout.getSpacingAdd(), true);

    canvas.save();
    canvas.translate( layout.getLineWidth(0) * 0.5f, 0.0f );
    layout.draw(canvas);
    canvas.restore();

但我确信这不是绘制轮廓的好方法。我不知道如何跟踪 TextView.getLayout() 对象中的更改。此外，它不适用于多行 TextView 和不同的重力。最终这段代码的性能非常差，因为它在每次绘制时都会分配一个 Layout 对象。我不太明白它是如何工作的，所以我不想使用它。

I've been trying to make it work for some time and I have a solution, but it's for a special case only! It's possible to get Layout object that is used inside the TextView for drawing text. You can create a copy of this object and use it inside the onDraw(Canvas) method.

    final Layout originalLayout = super.getLayout();
    final Layout layout = new StaticLayout(text, mStrokePaint,
    originalLayout.getWidth(), originalLayout.getAlignment(),
    originalLayout.getSpacingMultiplier(), originalLayout.getSpacingAdd(), true);

    canvas.save();
    canvas.translate( layout.getLineWidth(0) * 0.5f, 0.0f );
    layout.draw(canvas);
    canvas.restore();

But I'm sure that it's not a good way for drawing outlines. I don't know how to track changes in a TextView.getLayout() object. Also it doesn't work for multiline TextViews and different gravities. And eventually this code has very poor performance because it allocates a Layout object on every draw. I don't understand exactly how it works, so I'd prefer not to use it.

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故人如初 2024-10-12 18:45:29

TextView 类中有一些属性，例如 android:shadowColor、android:shadowDx、android:shadowDy > 和android:shadowRadius。在我看来，他们做的事情和你想要实现的事情是一样的。所以也许你应该首先尝试一个简单的 TextView 。