Develop Reference

Calculate max number of characters (having predefined size eg 20dp) that will fit in a text view android

I need to calculate how many characters (having pre-defined size eg 20dp) will fit on the text view to divide the long text into different Views? Like any reader app
I'm using the following code that works fine for a single line. My question is how to determine the max number of lines that will fit in text view in various screen sizes?
string abc = "This string is a loooong string";
final float densityMultiplier = getResources().getDisplayMetrics().density;
final float scaledPx = 20 * densityMultiplier;
int numChars;
Paint paint = txtArea.getPaint();
paint.setTextSize(scaledPx);
for (numChars = 1; numChars <= abc.length(); ++numChars)
{
if (paint.measureText(abc, 0, numChars) >= screenWidthDp)
{
break;
}
}

Simply use TextView.getLineHeight() to get height of a line

getTextWidths method is giving wrong result

There is a problem with some Paint class methods. I should get the width of spanned string given to the TextView. Let's say I'm measuring text at first row. When I measure it programmatically it gives 286, but the width of the screen is 240? Maybe someone had such a problem?Any help will be appreciated...
The code for calculating width of spanned text:
private int calcWidthSize(CharSequence spannedString, int currentSize) {
int res = 0;
Paint paint = new Paint();
float[] a= new float[444];
paint.setTextSize(currentSize);
paint.getTextWidths(spannedString,0,spannedString.length(),a);
for (int num=0;num<a.length;num++){
res+=(int)a[num];
}
return res;
}

Solved.The width of display is in pixels format and equals to 240.Text measure gives us result in dp format

Get absolute position for a given offset on TextView (Android)

I have a TextView in which I want to place a solid color block over given words of the TextView, for example:
"This is a text string, I want to put a rectangle over this WORD" - so, "WORD" would have a rectangle with a solid color over it.
To do this, I am thinking about overriding the onDraw(Canvas canvas) method, in order to draw a block over the text. My only problem is to find an efficient way to get the absolute position of a given word or character.
Basically, I am looking for something that does the exact opposite of the getOffsetForPosition(float x, float y) method

Based on this post: How get coordinate of a ClickableSpan inside a TextView?, I managed to use this code in order to put a rectangle on top of the text:
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.WHITE);
// Initialize global value
TextView parentTextView = this;
Rect parentTextViewRect = new Rect();
// Find where the WORD is
String targetWord = "WORD";
int startOffsetOfClickedText = this.getText().toString().indexOf(targetWord);
int endOffsetOfClickedText = startOffsetOfClickedText + targetWord.length();
// Initialize values for the computing of clickedText position
Layout textViewLayout = parentTextView.getLayout();
double startXCoordinatesOfClickedText = textViewLayout.getPrimaryHorizontal((int)startOffsetOfClickedText);
double endXCoordinatesOfClickedText = textViewLayout.getPrimaryHorizontal((int)endOffsetOfClickedText);
// Get the rectangle of the clicked text
int currentLineStartOffset = textViewLayout.getLineForOffset((int)startOffsetOfClickedText);
int currentLineEndOffset = textViewLayout.getLineForOffset((int)endOffsetOfClickedText);
boolean keywordIsInMultiLine = currentLineStartOffset != currentLineEndOffset;
textViewLayout.getLineBounds(currentLineStartOffset, parentTextViewRect);
// Update the rectangle position to his real position on screen
int[] parentTextViewLocation = {0,0};
parentTextView.getLocationOnScreen(parentTextViewLocation);
double parentTextViewTopAndBottomOffset = (
//parentTextViewLocation[1] -
parentTextView.getScrollY() +
parentTextView.getCompoundPaddingTop()
);
parentTextViewRect.top += parentTextViewTopAndBottomOffset;
parentTextViewRect.bottom += parentTextViewTopAndBottomOffset;
// In the case of multi line text, we have to choose what rectangle take
if (keywordIsInMultiLine){
WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
int screenHeight = display.getHeight();
int dyTop = parentTextViewRect.top;
int dyBottom = screenHeight - parentTextViewRect.bottom;
boolean onTop = dyTop > dyBottom;
if (onTop){
endXCoordinatesOfClickedText = textViewLayout.getLineRight(currentLineStartOffset);
}
else{
parentTextViewRect = new Rect();
textViewLayout.getLineBounds(currentLineEndOffset, parentTextViewRect);
parentTextViewRect.top += parentTextViewTopAndBottomOffset;
parentTextViewRect.bottom += parentTextViewTopAndBottomOffset;
startXCoordinatesOfClickedText = textViewLayout.getLineLeft(currentLineEndOffset);
}
}
parentTextViewRect.left += (
parentTextViewLocation[0] +
startXCoordinatesOfClickedText +
parentTextView.getCompoundPaddingLeft() -
parentTextView.getScrollX()
);
parentTextViewRect.right = (int) (
parentTextViewRect.left +
endXCoordinatesOfClickedText -
startXCoordinatesOfClickedText
);
canvas.drawRect(parentTextViewRect, paint);
}

You can use spans for that.
First you create a spannable for your text, like this:
Spannable span = new SpannableString(text);
Then you put a span around the word that you want to highlight, somewhat like this:
span.setSpan(new UnderlineSpan(), start, end,
Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
Unfortunately I don't know of an existing span that puts a border around a word. I found UnderlineSpan, and also BackgroundColorSpan, perhaps these are also useful for you, or you can have a look at the code and see if you can create a BorderSpan based on one of those.

Instead of drawing a rectangle over the WORD, you could simply replace its characters with an appropriate unicode symbol like U+25AE (▮ Black vertical rectangle).
So you'd get
"This is a text string, I want to put a rectangle over this ▮▮▮▮"
If that is sufficient. See for example Wikipedia for a wast list of unicode symbols.
If you actually need to paint that black box you can do the following as long as your text is in a single line:
Calculate the width of the text part before 'WORD' as explained here to find the left edge of the box and calcuate the width of 'WORD' using the same method to find the width of the box.
For a multiline text the explained method might also work but I think you'll have to do quite a lot of work here.

use getLayout().getLineBottom and textpaint.measureText to manually do the reverse calculation of getOffsetForPosition.
below is an example of using the calculated x,y for some textOffset to position the handle drawable when the textview gets clicked.
class TextViewCustom extends TextView{
float lastX,lastY;
#Override
public boolean onTouchEvent(MotionEvent event) {
boolean ret = super.onTouchEvent(event);
lastX=event.getX();
lastY=event.getY();
return ret;
}
BreakIterator boundary;
Drawable handleLeft;
private void init() {// call it in constructors
boundary = BreakIterator.getWordInstance();
handleLeft=getResources().getDrawable(R.drawable.abc_text_select_handle_left_mtrl_dark);
setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
int line = getLayout().getLineForVertical((int) lastY);
int offset = getLayout().getOffsetForHorizontal(line, lastX);
int wordEnd = boundary.following(offset);
int wordStart = boundary.previous();
CMN.Log(getText().subSequence(wordStart, wordEnd));
int y = getLayout().getLineBottom(line);
int trimA = getLayout().getLineStart(line);
float x = getPaddingLeft()+getPaint().measureText(getText(), trimA, wordStart);
x-=handleLeft.getIntrinsicWidth()*1.f*9/12;
handleLeft.setBounds((int)x,y,(int)(x+handleLeft.getIntrinsicWidth()),y+handleLeft.getIntrinsicHeight());
invalidate();
}
});
}
#Override
public void setText(CharSequence text, BufferType type) {
super.setText(text, type);
if(boundary!=null)
boundary.setText(text.toString());
}
}

How can I get the height of a given string's descender?

How can I get the height of a given string's descender?
For instance,
abc should return 0.
abcl should return 0.
abcp should return distance from descnder line to baseline.
abclp should return distance from descnder line to baseline.
The best I could came out so far is
private int getDecender(String string, Paint paint) {
// Append "l", to ensure there is Ascender
string = string + "l";
final String stringWithoutDecender = "l";
final Rect bounds = new Rect();
final Rect boundsForStringWithoutDecender = new Rect();
paint.getTextBounds(string, 0, string.length(), bounds);
paint.getTextBounds(stringWithoutDecender, 0, stringWithoutDecender.length(), boundsForStringWithoutDecender);
return bounds.height() - boundsForStringWithoutDecender.height();
}
However, my code smell is that they are not good enough. Is there any better and faster way?

Actually I was looking for the same functionality. It turns out there is much simpler way,
you do not even need separate function for that.
If you just call getTextBounds() on a given string, the returned bounding box will already have that information.
For example:
paint.getTextBounds(exampleString1 , 0, exampleString1.length(), bounds);
if (bounds.bottom > 0) Log.i("Test", "String HAS descender");
else Log.i("Test", "String DOES NOT HAVE descender");
Simply saying bounds.top tells you the ascent of the string (it has negative value as Y axis 0 point is at the baseline of the string) and bounds.bottom tells you the descent of the string (which can be 0 or positive value for strings having descent).

You should have a look at Paint.FontMetrics. The descent member will give you "The recommended distance below the baseline for singled spaced text.".

Measuring text height to be drawn on Canvas ( Android )

Any straight forward way to measure the height of text?
The way I am doing it now is by using Paint's measureText() to get the width, then by trial and error finding a value to get an approximate height. I've also been messing around with FontMetrics, but all these seem like approximate methods that suck.
I am trying to scale things for different resolutions. I can do it, but I end up with incredibly verbose code with lots of calculations to determine relative sizes. I hate it! There has to be a better way.

There are different ways to measure the height depending on what you need.
#1 getTextBounds
If you are doing something like precisely centering a small amount of fixed text, you probably want getTextBounds. You can get the bounding rectangle like this
Rect bounds = new Rect();
mTextPaint.getTextBounds(mText, 0, mText.length(), bounds);
int height = bounds.height();
As you can see for the following images, different strings will give different heights (shown in red).
These differing heights could be a disadvantage in some situations when you just need a constant height no matter what the text is. See the next section.
#2 Paint.FontMetrics
You can calculate the hight of the font from the font metrics. The height is always the same because it is obtained from the font, not any particular text string.
Paint.FontMetrics fm = mTextPaint.getFontMetrics();
float height = fm.descent - fm.ascent;
The baseline is the line that the text sits on. The descent is generally the furthest a character will go below the line and the ascent is generally the furthest a character will go above the line. To get the height you have to subtract ascent because it is a negative value. (The baseline is y=0 and y descreases up the screen.)
Look at the following image. The heights for both of the strings are 234.375.
If you want the line height rather than just the text height, you could do the following:
float height = fm.bottom - fm.top + fm.leading; // 265.4297
These are the bottom and top of the line. The leading (interline spacing) is usually zero, but you should add it anyway.
The images above come from this project. You can play around with it to see how Font Metrics work.
#3 StaticLayout
For measuring the height of multi-line text you should use a StaticLayout. I talked about it in some detail in this answer, but the basic way to get this height is like this:
String text = "This is some text. This is some text. This is some text. This is some text. This is some text. This is some text.";
TextPaint myTextPaint = new TextPaint();
myTextPaint.setAntiAlias(true);
myTextPaint.setTextSize(16 * getResources().getDisplayMetrics().density);
myTextPaint.setColor(0xFF000000);
int width = 200;
Layout.Alignment alignment = Layout.Alignment.ALIGN_NORMAL;
float spacingMultiplier = 1;
float spacingAddition = 0;
boolean includePadding = false;
StaticLayout myStaticLayout = new StaticLayout(text, myTextPaint, width, alignment, spacingMultiplier, spacingAddition, includePadding);
float height = myStaticLayout.getHeight();

What about paint.getTextBounds() (object method)

#bramp's answer is correct - partially, in that it does not mention that the calculated boundaries will be the minimum rectangle that contains the text fully with implicit start coordinates of 0, 0.
This means, that the height of, for example "Py" will be different from the height of "py" or "hi" or "oi" or "aw" because pixel-wise they require different heights.
This by no means is an equivalent to FontMetrics in classic java.
While width of a text is not much of a pain, height is.
In particular, if you need to vertically center-align the drawn text, try getting the boundaries of the text "a" (without quotes), instead of using the text you intend to draw.
Works for me...
Here's what I mean:
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.LINEAR_TEXT_FLAG);
paint.setStyle(Paint.Style.FILL);
paint.setColor(color);
paint.setTextAlign(Paint.Align.CENTER);
paint.setTextSize(textSize);
Rect bounds = new Rect();
paint.getTextBounds("a", 0, 1, bounds);
buffer.drawText(this.myText, canvasWidth >> 1, (canvasHeight + bounds.height()) >> 1, paint);
// remember x >> 1 is equivalent to x / 2, but works much much faster
Vertically center aligning the text means vertically center align the bounding rectangle - which is different for different texts (caps, long letters etc). But what we actually want to do is to also align the baselines of rendered texts, such that they did not appear elevated or grooved. So, as long as we know the center of the smallest letter ("a" for example) we then can reuse its alignment for the rest of the texts. This will center align all the texts as well as baseline-align them.

The height is the text size you have set on the Paint variable.
Another way to find out the height is
mPaint.getTextSize();

You could use the android.text.StaticLayout class to specify the bounds required and then call getHeight(). You can draw the text (contained in the layout) by calling its draw(Canvas) method.

You can simply get the text size for a Paint object using getTextSize() method.
For example:
Paint mTextPaint = new Paint (Paint.ANTI_ALIAS_FLAG);
//use densityMultiplier to take into account different pixel densities
final float densityMultiplier = getContext().getResources()
.getDisplayMetrics().density;
mTextPaint.setTextSize(24.0f*densityMultiplier);
//...
float size = mTextPaint.getTextSize();

You must use Rect.width() and Rect.Height() which returned from getTextBounds() instead. That works for me.

If anyone still has problem, this is my code.
I have a custom view which is square (width = height) and I want to assign a character to it. onDraw() shows how to get height of character, although I'm not using it. Character will be displayed in the middle of view.
public class SideBarPointer extends View {
private static final String TAG = "SideBarPointer";
private Context context;
private String label = "";
private int width;
private int height;
public SideBarPointer(Context context) {
super(context);
this.context = context;
init();
}
public SideBarPointer(Context context, AttributeSet attrs) {
super(context, attrs);
this.context = context;
init();
}
public SideBarPointer(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.context = context;
init();
}
private void init() {
// setBackgroundColor(0x64FF0000);
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
height = this.getMeasuredHeight();
width = this.getMeasuredWidth();
setMeasuredDimension(width, width);
}
protected void onDraw(Canvas canvas) {
float mDensity = context.getResources().getDisplayMetrics().density;
float mScaledDensity = context.getResources().getDisplayMetrics().scaledDensity;
Paint previewPaint = new Paint();
previewPaint.setColor(0x0C2727);
previewPaint.setAlpha(200);
previewPaint.setAntiAlias(true);
Paint previewTextPaint = new Paint();
previewTextPaint.setColor(Color.WHITE);
previewTextPaint.setAntiAlias(true);
previewTextPaint.setTextSize(90 * mScaledDensity);
previewTextPaint.setShadowLayer(5, 1, 2, Color.argb(255, 87, 87, 87));
float previewTextWidth = previewTextPaint.measureText(label);
// float previewTextHeight = previewTextPaint.descent() - previewTextPaint.ascent();
RectF previewRect = new RectF(0, 0, width, width);
canvas.drawRoundRect(previewRect, 5 * mDensity, 5 * mDensity, previewPaint);
canvas.drawText(label, (width - previewTextWidth)/2, previewRect.top - previewTextPaint.ascent(), previewTextPaint);
super.onDraw(canvas);
}
public void setLabel(String label) {
this.label = label;
Log.e(TAG, "Label: " + label);
this.invalidate();
}
}