Question

我目前正致力于扩展TextView，在文本周围添加大纲。到目前为止，我遇到的唯一问题是我无法在文本背后正确定位“轮廓”。如果我像下面描述的那样对扩展类进行编码，我得到一个如下所示的标签：

注意：在上面的屏幕截图中，我将填充颜色设置为白色，将笔触颜色设置为黑色。

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);
    }
}

Answer 1

巴哈，那是我的愚蠢。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，我需要平均此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);

现在整个代码如下：

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);
    }
}

Answer 2

我已经暂时搁置了一些这样的例子，因为似乎没有一个正确排列，一旦我终于掌握了文本发生的事情并把我的数学帽子放在上面我改变了我的onDraw对于这个是以下，无论文本的大小或它包含视图的大小和形状，它都完美无缺......

@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);
}

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超级文本标志，不要强迫它居中。此处计算的drawText位置始终是描边文本的正确居中位置。

Answer 3

我一直试图让它工作一段时间，我有一个解决方案，但它仅适用于特殊情况！可以在Layout内使用TextView对象来绘制文本。您可以创建此对象的副本，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。我不明白它究竟是如何工作的，所以我宁愿不使用它。

Answer 4

TextView课程中有一些属性，例如android:shadowColor，android:shadowDx，android:shadowDy和android:shadowRadius。在我看来，他们做同样的事情你想要实现。所以也许你应该先尝试一个简单的TextView。

如何在TextView的扩展类中正确绘制文本？

4 个答案: