Calculate baseline y for drawing text on canvas in Android-CodePudding

I am using the following code to draw text.

    final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    final Rect rect = new Rect();
    paint.getTextBounds(text, 0, text.length(), rect);

    final int width = rect.width();
    final int height = rect.height();

    Bitmap rendered = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

    final Canvas gOfRendered = new Canvas(rendered);

    paint.setColor(Color.WHITE);

    gOfRendered.drawText(
            text, 0, height - paint.getFontMetrics().descent - paint.getFontMetrics().leading, paint
    );

    gOfRendered.drawColor(0x11ffffff); // to see the bounds

Canvas.drawText needs the y coordinate as a baseline. Some strings such as "back" in the above output does not have a descent. It gets cut and it does not make sense to subtract paint.getFontMetrics().descent in those cases. How do I make sure that the baseline is calculated correctly?

Alternately, is there a text drawing method which takes the origin y coordinate and not the baseline?

I am looking for a way to draw text exactly within the bounds given by Paint.getTextBounds()

CodePudding user response：

I use this function to draw multiline text:

void drawMultilineText(Canvas canvas, String text, float x, float y) {
    for (String line: text.split("\n")) {
        canvas.drawText(line, x, y, mPaintText);
        y  = mPaintText.descent() - mPaintText.ascent();
    }
}

Please also check

activity_main.xml

<androidx.constraintlayout.widget.ConstraintLayout 
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.example.textbaseline.MyView
        android:id="@ id/myView2"
        android:layout_width="200dp"
        android:layout_height="75dp"
        android:layout_margin="8dp"
        android:background="@android:color/black"
        android:text="apple"
        app:layout_constraintBottom_toTopOf="@ id/myView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_chainStyle="packed" />

    <com.example.textbaseline.MyView
        android:id="@ id/myView"
        android:layout_width="200dp"
        android:layout_height="75dp"
        android:layout_margin="8dp"
        android:background="@android:color/black"
        android:text="Retrograde"
        app:layout_constraintBottom_toTopOf="@ id/myView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@ id/myView2" />

    <com.example.textbaseline.MyView
        android:id="@ id/myView3"
        android:layout_width="200dp"
        android:layout_height="75dp"
        android:background="@android:color/black"
        android:text="back"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@ id/myView" />

</androidx.constraintlayout.widget.ConstraintLayout>