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Measure and layout properly
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Fulfil the onMeasure contract by allowing AT_MOST and UNSPECIFIED specs
instead of failing at runtime. In addition, use the view's padding to
make child views smaller, the way it should be. There is one problem,
which is that the ViewFlowIndicator implementations assume that the
scrolled region is the whole width of the container, whereas it might
actually be smaller, so they show wrong positions if left/right padding
is non-zero. This will probably require an interface change to fix.
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@orac
orac committed Jul 16, 2013
1 parent 0c77791 commit 97740a6
Showing 1 changed file with 114 additions and 57 deletions.
171 changes: 114 additions & 57 deletions viewflow/src/org/taptwo/android/widget/ViewFlow.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
Expand All @@ -15,27 +15,21 @@
*/
package org.taptwo.android.widget;

import java.util.EnumSet;
import java.util.LinkedList;

import org.taptwo.android.widget.viewflow.R;

import android.content.Context;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.*;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.widget.AbsListView;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.Scroller;
import org.taptwo.android.widget.viewflow.R;

import java.util.EnumSet;
import java.util.LinkedList;

/**
* A horizontally scrollable {@link ViewGroup} with items populated from an
Expand Down Expand Up @@ -74,6 +68,9 @@ public class ViewFlow extends AdapterView<Adapter> {
private AdapterDataSetObserver mDataSetObserver;
private FlowIndicator mIndicator;
private int mLastOrientation = -1;
/** Extra return value from obtainView: tells you whether the item it returned on the last call was recycled rather than created by the adapter.
* This is a member because getting a second return value requires an allocation. */
private boolean mLastObtainedViewWasRecycled = false;

private OnGlobalLayoutListener orientationChangeListener = new OnGlobalLayoutListener() {

Expand All @@ -94,9 +91,9 @@ public static interface ViewSwitchListener {
* This method is called when a new View has been scrolled to.
*
* @param view
* the {@link View} currently in focus.
* the {@link View} currently in focus.
* @param position
* The position in the adapter of the {@link View} currently in focus.
* The position in the adapter of the {@link View} currently in focus.
*/
void onSwitched(View view, int position);

Expand Down Expand Up @@ -153,44 +150,90 @@ public int getViewsCount() {

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);

final int width = MeasureSpec.getSize(widthMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode != MeasureSpec.EXACTLY && !isInEditMode()) {
throw new IllegalStateException(
"ViewFlow can only be used in EXACTLY mode.");
}

final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (heightMode != MeasureSpec.EXACTLY && !isInEditMode()) {
throw new IllegalStateException(
"ViewFlow can only be used in EXACTLY mode.");

int childWidth = 0;
int childHeight = 0;
int childState = 0;

final int widthPadding = getWidthPadding();
final int heightPadding = getHeightPadding();

int count = mAdapter == null ? 0 : mAdapter.getCount();
if (count > 0 && (widthMode == MeasureSpec.UNSPECIFIED || widthMode == MeasureSpec.AT_MOST ||
heightMode == MeasureSpec.UNSPECIFIED)) {
final View child = obtainView(0);

int childTargetWidthSpec = widthMeasureSpec;
if (widthMode == MeasureSpec.AT_MOST) {
int childTargetSize = widthSize - widthPadding;
childTargetWidthSpec = MeasureSpec.makeMeasureSpec(childTargetSize, MeasureSpec.AT_MOST);
}
child.measure(childTargetWidthSpec, heightMeasureSpec);
childWidth = child.getMeasuredWidth();
childHeight = child.getMeasuredHeight();
childState = child.getMeasuredState();
mRecycledViews.add(child);
}
if (widthMode == MeasureSpec.UNSPECIFIED) {
widthSize = childWidth + widthPadding;
} else if (widthMode == MeasureSpec.AT_MOST) {
widthSize = childWidth + widthPadding;
widthSize = resolveSizeAndState(widthSize, widthMeasureSpec, childState);
}

// The children are given the same width and height as the workspace
final int count = getChildCount();
for (int i = 0; i < count; i++) {
getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
if (heightMode == MeasureSpec.UNSPECIFIED) {
heightSize = heightPadding + childHeight;
} else {
heightSize |= (childState&MEASURED_STATE_MASK);
}

setMeasuredDimension(widthSize, heightSize);
}

private int getWidthPadding() {
return getPaddingLeft() + getPaddingRight() + getHorizontalFadingEdgeLength() * 2;
}

private int getChildWidth() {
return getWidth() - getWidthPadding();
}

private int getHeightPadding() {
return getPaddingTop() + getPaddingBottom();
}

private int getChildHeight() {
return getHeight() - getHeightPadding();
}

@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);

measureChildren(
MeasureSpec.makeMeasureSpec(w - getWidthPadding(), MeasureSpec.AT_MOST),
MeasureSpec.makeMeasureSpec(h - getHeightPadding(), MeasureSpec.AT_MOST));

if (mFirstLayout) {
mScroller.startScroll(0, 0, mCurrentScreen * width, 0, 0);
mScroller.startScroll(0, 0, mCurrentScreen * w, 0, 0);
mFirstLayout = false;
}
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int childLeft = 0;
int childLeft = getPaddingLeft() + getHorizontalFadingEdgeLength();

final int count = getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != View.GONE) {
final int childWidth = child.getMeasuredWidth();
child.layout(childLeft, 0, childLeft + childWidth,
child.getMeasuredHeight());
child.layout(childLeft, getPaddingTop(), childLeft + childWidth,
getPaddingTop() + child.getMeasuredHeight());
childLeft += childWidth;
}
}
Expand Down Expand Up @@ -253,7 +296,7 @@ public boolean onInterceptTouchEvent(MotionEvent ev) {
} else if (deltaX > 0) {
final int availableToScroll = getChildAt(
getChildCount() - 1).getRight()
- scrollX - getWidth();
- scrollX - getChildWidth();
if (availableToScroll > 0) {
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
Expand Down Expand Up @@ -351,7 +394,7 @@ public boolean onTouchEvent(MotionEvent ev) {
} else if (deltaX > 0) {
final int availableToScroll = getChildAt(
getChildCount() - 1).getRight()
- scrollX - getWidth();
- scrollX - getChildWidth();
if (availableToScroll > 0) {
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
Expand Down Expand Up @@ -419,13 +462,13 @@ protected void onScrollChanged(int h, int v, int oldh, int oldv) {
* horizontal scroll origin here, since we use a view buffer.
*/
int hPerceived = h + (mCurrentAdapterIndex - mCurrentBufferIndex)
* getWidth();
* getChildWidth();
mIndicator.onScrolled(hPerceived, v, oldh, oldv);
}
}

private void snapToDestination() {
final int screenWidth = getWidth();
final int screenWidth = getChildWidth();
final int whichScreen = (getScrollX() + (screenWidth / 2))
/ screenWidth;

Expand All @@ -441,7 +484,7 @@ private void snapToScreen(int whichScreen) {

mNextScreen = whichScreen;

final int newX = whichScreen * getWidth();
final int newX = whichScreen * getChildWidth();
final int delta = newX - getScrollX();
mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 2);
invalidate();
Expand All @@ -464,12 +507,12 @@ public void computeScroll() {
* Scroll to the {@link View} in the view buffer specified by the index.
*
* @param indexInBuffer
* Index of the view in the view buffer.
* Index of the view in the view buffer.
*/
private void setVisibleView(int indexInBuffer, boolean uiThread) {
mCurrentScreen = Math.max(0,
Math.min(indexInBuffer, getChildCount() - 1));
int dx = (mCurrentScreen * getWidth()) - mScroller.getCurrX();
int dx = (mCurrentScreen * getChildWidth()) - mScroller.getCurrX();
mScroller.startScroll(mScroller.getCurrX(), mScroller.getCurrY(), dx,
0, 0);
if(dx == 0)
Expand All @@ -485,7 +528,7 @@ private void setVisibleView(int indexInBuffer, boolean uiThread) {
* ViewFlow} scrolls.
*
* @param l
* the scroll listener
* the scroll listener
*/
public void setOnViewSwitchListener(ViewSwitchListener l) {
mViewSwitchListener = l;
Expand Down Expand Up @@ -529,10 +572,10 @@ public View getSelectedView() {
.get(mCurrentBufferIndex) : null);
}

@Override
public int getSelectedItemPosition() {
return mCurrentAdapterIndex;
}
@Override
public int getSelectedItemPosition() {
return mCurrentAdapterIndex;
}

/**
* Set the FlowIndicator
Expand Down Expand Up @@ -675,30 +718,44 @@ private void postViewSwitched(int direction) {
logBuffer();
}

@Override protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
final LayoutParams lp = child.getLayoutParams();
assert lp != null;
lp.height = getChildHeight();
lp.width = getChildWidth();
final int childWidthSpec = MeasureSpec.makeMeasureSpec(lp.width, MeasureSpec.EXACTLY);
final int childHeightSpec = MeasureSpec.makeMeasureSpec(lp.height, MeasureSpec.EXACTLY);
child.measure(childWidthSpec, childHeightSpec);
}

private View setupChild(View child, boolean addToEnd, boolean recycle) {
ViewGroup.LayoutParams p = (ViewGroup.LayoutParams) child
.getLayoutParams();
if (p == null) {
p = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT, 0);
}
final LayoutParams lp = child.getLayoutParams();
assert lp != null;
measureChild(child, 0, 0);
if (recycle)
attachViewToParent(child, (addToEnd ? -1 : 0), p);
attachViewToParent(child, (addToEnd ? -1 : 0), lp);
else
addViewInLayout(child, (addToEnd ? -1 : 0), p, true);
addViewInLayout(child, (addToEnd ? -1 : 0), lp, true);
return child;
}

private View makeAndAddView(int position, boolean addToEnd) {
return makeAndAddView(position, addToEnd, getRecycledView());
View view = obtainView(position);
return setupChild(view, addToEnd, mLastObtainedViewWasRecycled);
}

private View makeAndAddView(int position, boolean addToEnd, View convertView) {
private View obtainView(int position) {
View convertView = getRecycledView();
View view = mAdapter.getView(position, convertView, this);
if(view != convertView && convertView != null)
mRecycledViews.add(convertView);
return setupChild(view, addToEnd, view == convertView);
mLastObtainedViewWasRecycled = (view == convertView);
ViewGroup.LayoutParams p = view.getLayoutParams();
if (p == null) {
p = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
view.setLayoutParams(p);
}
return view;
}

class AdapterDataSetObserver extends DataSetObserver {
Expand Down

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