/**
* Recursive function to find all viable candidate combinations for laying out the next three
* rows.
*/
private void generateCombos(int imageIndex) {
if (mCombosGenerated >= MAX_COMBOS) {
// Consider a maximum of 30 combinations for any iteration of this.
return;
}
if (mPartialCombo.size() == MAX_ROWS_PER_COMBO || imageIndex == mImageCount) {
// If the partial combo contains max rows OR we are out of images, this combination
// is complete.
StringBuilder builder = null;
if (DEBUG_COMBOS) {
builder = new StringBuilder();
builder.append('[');
builder.append(mPartialCombo.computeScore());
builder.append("] ");
for (int i = 0; i < mPartialCombo.size(); i++) {
if (i != 0) {
builder.append(", ");
}
Row row = mPartialCombo.getRow(i);
builder.append(row.startIndex());
builder.append(" - ");
builder.append(row.startIndex() + row.size() - 1);
}
}
// Increment number of combos that have been generated.
mCombosGenerated++;
float scoreDiff =
mBestCombo == null ? -1f : mPartialCombo.computeScore() - mBestCombo.computeScore();
// Pseudo-randomly decide whether to select between combos of equal score.
if (scoreDiff == 0f) {
mSameScoreCount++;
int randomInt = mRandom.nextInt(mSameScoreCount);
scoreDiff = (randomInt == 0) ? -1 : 1;
} else if (scoreDiff < 0f) {
mSameScoreCount = 1;
}
if (scoreDiff < 0f) {
// Found new best combo, so save it (as a clone, since the partial combo wil continue
// to be modified during combo generation.
mBestCombo = mPartialCombo.clone();
}
if (DEBUG_COMBOS) {
if (scoreDiff < 0f) {
// Indicate in the log that the combo was selected as current best.
builder.append(" ***");
}
Log.d("DebugCombos", builder.toString());
}
return;
}
// For the current partial combination, compute possibilities for the next row. We will
// consider each row of ideal height, plus up to one overheight and one underheight row.
Row row = new Row(imageIndex);
int overHeightSize = 0;
for (int i = imageIndex; i < mImageCount; i++) {
// Add photo to next row under consideration.
row.addImage();
if (row.getAspect() < mMinRowAspect) {
overHeightSize++;
} else {
// Add this row to the current partial combination and calculate the next set of
// possible rows.
mPartialCombo.addRow(row.clone());
generateCombos(i + 1);
mPartialCombo.removeRow();
if (row.getAspect() > mMaxRowAspect) {
break;
}
}
}
if (overHeightSize > 0) {
mPartialCombo.addRow(new Row(imageIndex, overHeightSize));
generateCombos(imageIndex + overHeightSize);
mPartialCombo.removeRow();
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// Fill any available width.
int measuredWidth = MeasureSpec.getSize(widthMeasureSpec);
// Don't re-measure everything unless width changes.
if (mMeasuredWidth != measuredWidth) {
mMeasuredWidth = measuredWidth;
// From the full list of images, repeatedly carve off individual rows. Rows will be
// selected to ensure a minimal amount of cropping while maintaining the aspect ratio of
// each individual bitmap.
int imageIndex = 0;
while (imageIndex < mImageCount) {
// To determine the next row, lay out the next three rows in ideal fashion and take the
// first row.
// This is accomplished by calculating a number of possible combinations for the next three
// rows
// and scoring each combination. The first row of the highest scoring combination will be
// accepted.
Assert.assertTrue(mPartialCombo.size() == 0);
mBestCombo = null;
mCombosGenerated = 0;
mSameScoreCount = 0;
if (DEBUG_COMBOS) {
Log.d("DebugCombos", "ROW #" + (mLayoutRows.size() + 1));
}
generateCombos(imageIndex);
// Add first row from highest scoring combo to the list of rows for layout.
Row row = mBestCombo.getRow(0);
mLayoutRows.add(row);
// Skip past images that are already laid out.
imageIndex += row.size();
}
// Calculate total height by adding together height of all rows.
mMeasuredHeight = 0;
for (int i = 0; i < mLayoutRows.size(); i++) {
Row row = mLayoutRows.get(i);
row.measure(mMeasuredWidth);
mMeasuredHeight += row.getMeasuredHeight();
mMeasuredHeight += mBorderSize;
}
}
// Height may be constrained by container.
int measuredHeight = mMeasuredHeight;
switch (MeasureSpec.getMode(heightMeasureSpec)) {
case MeasureSpec.AT_MOST:
measuredHeight = Math.min(mMeasuredHeight, MeasureSpec.getSize(heightMeasureSpec));
break;
case MeasureSpec.EXACTLY:
measuredHeight = MeasureSpec.getSize(heightMeasureSpec);
break;
}
setMeasuredDimension(measuredWidth, measuredHeight);
}