diff options
Diffstat (limited to 'src/com/android/calculator2/CalculatorResult.java')
| -rw-r--r-- | src/com/android/calculator2/CalculatorResult.java | 89 |
1 files changed, 68 insertions, 21 deletions
diff --git a/src/com/android/calculator2/CalculatorResult.java b/src/com/android/calculator2/CalculatorResult.java index d14135c..a916c30 100644 --- a/src/com/android/calculator2/CalculatorResult.java +++ b/src/com/android/calculator2/CalculatorResult.java @@ -48,7 +48,7 @@ import android.support.v4.view.ViewCompat; // A text widget that is "infinitely" scrollable to the right, // and obtains the text to display via a callback to Logic. public class CalculatorResult extends TextView { - static final int MAX_RIGHT_SCROLL = 100000000; + static final int MAX_RIGHT_SCROLL = 10000000; static final int INVALID = MAX_RIGHT_SCROLL + 10000; // A larger value is unlikely to avoid running out of space final OverScroller mScroller; @@ -71,8 +71,10 @@ public class CalculatorResult extends TextView { // Large positive values mean the decimal point is scrolled off the // left of the display. Zero means decimal point is barely displayed // on the right. - private int mLastPos; // Position already reflected in display. - private int mMinPos; // Maximum position before all digits disappear of the right. + private int mLastPos; // Position already reflected in display. Pixels. + private int mMinPos; // Minimum position before all digits disappear off the right. Pixels. + private int mMaxPos; // Maximum position before we start displaying the infinite + // sequence of trailing zeroes on the right. Pixels. private Object mWidthLock = new Object(); // Protects the next two fields. private int mWidthConstraint = -1; @@ -109,14 +111,14 @@ public class CalculatorResult extends TextView { // Ignore scrolls of error string, etc. if (!mScrollable) return true; mScroller.fling(mCurrentPos, 0, - (int) velocityX, 0 /* horizontal only */, - mMinPos, MAX_RIGHT_SCROLL, 0, 0); + mMinPos, mMaxPos, 0, 0); ViewCompat.postInvalidateOnAnimation(CalculatorResult.this); return true; } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { - // TODO: Should we be dealing with any edge effects here? + int distance = (int)distanceX; if (!mScroller.isFinished()) { mCurrentPos = mScroller.getFinalX(); } @@ -124,9 +126,14 @@ public class CalculatorResult extends TextView { stopActionMode(); CalculatorResult.this.cancelLongPress(); if (!mScrollable) return true; + if (mCurrentPos + distance < mMinPos) { + distance = mMinPos - mCurrentPos; + } else if (mCurrentPos + distance > mMaxPos) { + distance = mMaxPos - mCurrentPos; + } int duration = (int)(e2.getEventTime() - e1.getEventTime()); if (duration < 1 || duration > 100) duration = 10; - mScroller.startScroll(mCurrentPos, 0, (int)distanceX, 0, (int)duration); + mScroller.startScroll(mCurrentPos, 0, distance, 0, (int)duration); ViewCompat.postInvalidateOnAnimation(CalculatorResult.this); return true; } @@ -177,18 +184,45 @@ public class CalculatorResult extends TextView { } } - // Display a new result, given initial displayed - // precision and the string representing the whole part of - // the number to be displayed. - // We pass the string, instead of just the length, so we have - // one less place to fix in case we ever decide to - // correctly use a variable width font. - void displayResult(int initPrec, String truncatedWholePart) { + // Given that the last non-zero digit is at pos, compute the precision we have to ask + // ask for to actually get the digit at pos displayed. This is not an identity + // function, since we may need to drop digits to the right to make room for the exponent. + private int addExpSpace(int lastDigit) { + if (lastDigit < getMaxChars() - 1) { + // The decimal point will be in view when displaying the rightmost digit. + // no exponent needed. + // TODO: This will change if we stop scrolling to the left of the decimal + // point, which might be desirable in the traditional scientific notation case. + return lastDigit; + } + // When the last digit is displayed, the exponent will look like "e-<lastDigit>". + // The length of that string is the extra precision we need. + return lastDigit + (int)Math.ceil(Math.log10((double)lastDigit)) + 2; + } + + // Display a new result, given initial displayed precision, position of the rightmost + // nonzero digit (or Integer.MAX_VALUE if non-terminating), and the string representing + // the whole part of the number to be displayed. + // We pass the string, instead of just the length, so we have one less place to fix in case + // we ever decide to fully handle a variable width font. + void displayResult(int initPrec, int leastDigPos, String truncatedWholePart) { mLastPos = INVALID; synchronized(mWidthLock) { mCurrentPos = initPrec * mCharWidth; } - mMinPos = - (int) Math.ceil(getPaint().measureText(truncatedWholePart)); + // Should logically be + // mMinPos = - (int) Math.ceil(getPaint().measureText(truncatedWholePart)), but + // we eventually transalate to a character position by dividing by mCharWidth. + // To avoid rounding issues, we use the analogous computation here. + mMinPos = - truncatedWholePart.length() * mCharWidth; + if (leastDigPos < MAX_RIGHT_SCROLL) { + mMaxPos = Math.min(addExpSpace(leastDigPos) * mCharWidth, MAX_RIGHT_SCROLL); + } else { + mMaxPos = MAX_RIGHT_SCROLL; + } + mScrollable = (leastDigPos != (initPrec == -1 ? 0 : initPrec)); + // We assume that initPrec allows most significant digit to be displayed. + // If there is nothing to the right of initPrec, there is no point in scrolling. redisplay(); } @@ -212,8 +246,6 @@ public class CalculatorResult extends TextView { // would have been in had we not done so. // This minimizes jumps as a result of scrolling. Result is NOT internationalized, // uses "e" for exponent. - // last_included[0] is set to the position of the last digit we actually include; - // thus caller can tell whether result is exact. public String formatResult(String res, int digs, int maxDigs, boolean truncated, boolean negative) { @@ -313,13 +345,16 @@ public class CalculatorResult extends TextView { return (currentCharPos >= BoundedRational.digitsRequired(rat)); } - // May be called asynchronously from non-UI thread. + /** + * Return the maximum number of characters that will fit in the result display. + * May be called asynchronously from non-UI thread. + */ int getMaxChars() { - // We only use 2/3 of the available space, since the left 1/3 of the result is not - // visible when it is shown in large size. + // We only use 4/5 of the available space, since at least the left 4/5 of the result + // is not visible when it is shown in large size. int result; synchronized(mWidthLock) { - result = 2 * mWidthConstraint / (3 * mCharWidth); + result = 4 * mWidthConstraint / (5 * mCharWidth); // We can apparently finish evaluating before onMeasure in CalculatorText has been // called, in which case we get 0 or -1 as the width constraint. } @@ -331,6 +366,19 @@ public class CalculatorResult extends TextView { } } + /** + * Return the fraction of the available character space occupied by the + * current result. + * Should be called only with a valid result displayed. + */ + float getOccupancy() { + if (mScrollable) { + return 1.0f; + } else { + return (float)getText().length() / getMaxChars(); + } + } + int getCurrentCharPos() { synchronized(mWidthLock) { return mCurrentPos/mCharWidth; @@ -359,7 +407,6 @@ public class CalculatorResult extends TextView { setText(result); } mValid = true; - mScrollable = true; } @Override |