Java tutorial
/* * Copyright (C) 2014 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * 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 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.support.v7.internal.widget; import android.content.Context; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.support.v4.graphics.drawable.DrawableCompat; import android.support.v7.graphics.drawable.DrawableWrapper; import android.util.AttributeSet; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.ListAdapter; import android.widget.ListView; import java.lang.reflect.Field; /** * This class contains a number of useful things for ListView. Mainly used by * {@link android.support.v7.widget.ListPopupWindow}. * * @hide */ public class ListViewCompat extends ListView { public static final int INVALID_POSITION = -1; public static final int NO_POSITION = -1; private static final int[] STATE_SET_NOTHING = new int[] { 0 }; final Rect mSelectorRect = new Rect(); int mSelectionLeftPadding = 0; int mSelectionTopPadding = 0; int mSelectionRightPadding = 0; int mSelectionBottomPadding = 0; private Field mIsChildViewEnabled; private GateKeeperDrawable mSelector; public ListViewCompat(Context context) { this(context, null); } public ListViewCompat(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ListViewCompat(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); try { mIsChildViewEnabled = AbsListView.class.getDeclaredField("mIsChildViewEnabled"); mIsChildViewEnabled.setAccessible(true); } catch (NoSuchFieldException e) { e.printStackTrace(); } } @Override public void setSelector(Drawable sel) { mSelector = sel != null ? new GateKeeperDrawable(sel) : null; super.setSelector(mSelector); final Rect padding = new Rect(); if (sel != null) { sel.getPadding(padding); } mSelectionLeftPadding = padding.left; mSelectionTopPadding = padding.top; mSelectionRightPadding = padding.right; mSelectionBottomPadding = padding.bottom; } @Override protected void drawableStateChanged() { super.drawableStateChanged(); setSelectorEnabled(true); updateSelectorStateCompat(); } @Override protected void dispatchDraw(Canvas canvas) { final boolean drawSelectorOnTop = false; if (!drawSelectorOnTop) { drawSelectorCompat(canvas); } super.dispatchDraw(canvas); } protected void updateSelectorStateCompat() { Drawable selector = getSelector(); if (selector != null && shouldShowSelectorCompat()) { selector.setState(getDrawableState()); } } protected boolean shouldShowSelectorCompat() { return touchModeDrawsInPressedStateCompat() && isPressed(); } protected boolean touchModeDrawsInPressedStateCompat() { return false; } protected void drawSelectorCompat(Canvas canvas) { if (!mSelectorRect.isEmpty()) { final Drawable selector = getSelector(); if (selector != null) { selector.setBounds(mSelectorRect); selector.draw(canvas); } } } /** * Find a position that can be selected (i.e., is not a separator). * * @param position The starting position to look at. * @param lookDown Whether to look down for other positions. * @return The next selectable position starting at position and then searching either up or * down. Returns {@link #INVALID_POSITION} if nothing can be found. */ public int lookForSelectablePosition(int position, boolean lookDown) { final ListAdapter adapter = getAdapter(); if (adapter == null || isInTouchMode()) { return INVALID_POSITION; } final int count = adapter.getCount(); if (!getAdapter().areAllItemsEnabled()) { if (lookDown) { position = Math.max(0, position); while (position < count && !adapter.isEnabled(position)) { position++; } } else { position = Math.min(position, count - 1); while (position >= 0 && !adapter.isEnabled(position)) { position--; } } if (position < 0 || position >= count) { return INVALID_POSITION; } return position; } else { if (position < 0 || position >= count) { return INVALID_POSITION; } return position; } } protected void positionSelectorLikeTouchCompat(int position, View sel, float x, float y) { positionSelectorLikeFocusCompat(position, sel); Drawable selector = getSelector(); if (selector != null && position != INVALID_POSITION) { DrawableCompat.setHotspot(selector, x, y); } } protected void positionSelectorLikeFocusCompat(int position, View sel) { // If we're changing position, update the visibility since the selector // is technically being detached from the previous selection. final Drawable selector = getSelector(); final boolean manageState = selector != null && position != INVALID_POSITION; if (manageState) { selector.setVisible(false, false); } positionSelectorCompat(position, sel); if (manageState) { final Rect bounds = mSelectorRect; final float x = bounds.exactCenterX(); final float y = bounds.exactCenterY(); selector.setVisible(getVisibility() == VISIBLE, false); DrawableCompat.setHotspot(selector, x, y); } } protected void positionSelectorCompat(int position, View sel) { final Rect selectorRect = mSelectorRect; selectorRect.set(sel.getLeft(), sel.getTop(), sel.getRight(), sel.getBottom()); // Adjust for selection padding. selectorRect.left -= mSelectionLeftPadding; selectorRect.top -= mSelectionTopPadding; selectorRect.right += mSelectionRightPadding; selectorRect.bottom += mSelectionBottomPadding; try { // AbsListView.mIsChildViewEnabled controls the selector's state so we need to // modify it's value final boolean isChildViewEnabled = mIsChildViewEnabled.getBoolean(this); if (sel.isEnabled() != isChildViewEnabled) { mIsChildViewEnabled.set(this, !isChildViewEnabled); if (position != INVALID_POSITION) { refreshDrawableState(); } } } catch (IllegalAccessException e) { e.printStackTrace(); } } /** * Measures the height of the given range of children (inclusive) and returns the height * with this ListView's padding and divider heights included. If maxHeight is provided, the * measuring will stop when the current height reaches maxHeight. * * @param widthMeasureSpec The width measure spec to be given to a child's * {@link View#measure(int, int)}. * @param startPosition The position of the first child to be shown. * @param endPosition The (inclusive) position of the last child to be * shown. Specify {@link #NO_POSITION} if the last child * should be the last available child from the adapter. * @param maxHeight The maximum height that will be returned (if all the * children don't fit in this value, this value will be * returned). * @param disallowPartialChildPosition In general, whether the returned height should only * contain entire children. This is more powerful--it is * the first inclusive position at which partial * children will not be allowed. Example: it looks nice * to have at least 3 completely visible children, and * in portrait this will most likely fit; but in * landscape there could be times when even 2 children * can not be completely shown, so a value of 2 * (remember, inclusive) would be good (assuming * startPosition is 0). * @return The height of this ListView with the given children. */ public int measureHeightOfChildrenCompat(int widthMeasureSpec, int startPosition, int endPosition, final int maxHeight, int disallowPartialChildPosition) { final int paddingTop = getListPaddingTop(); final int paddingBottom = getListPaddingBottom(); final int paddingLeft = getListPaddingLeft(); final int paddingRight = getListPaddingRight(); final int reportedDividerHeight = getDividerHeight(); final Drawable divider = getDivider(); final ListAdapter adapter = getAdapter(); if (adapter == null) { return paddingTop + paddingBottom; } // Include the padding of the list int returnedHeight = paddingTop + paddingBottom; final int dividerHeight = ((reportedDividerHeight > 0) && divider != null) ? reportedDividerHeight : 0; // The previous height value that was less than maxHeight and contained // no partial children int prevHeightWithoutPartialChild = 0; View child = null; int viewType = 0; int count = adapter.getCount(); for (int i = 0; i < count; i++) { int newType = adapter.getItemViewType(i); if (newType != viewType) { child = null; viewType = newType; } child = adapter.getView(i, child, this); // Compute child height spec int heightMeasureSpec; final ViewGroup.LayoutParams childLp = child.getLayoutParams(); if (childLp != null && childLp.height > 0) { heightMeasureSpec = MeasureSpec.makeMeasureSpec(childLp.height, MeasureSpec.EXACTLY); } else { heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); } child.measure(widthMeasureSpec, heightMeasureSpec); if (i > 0) { // Count the divider for all but one child returnedHeight += dividerHeight; } returnedHeight += child.getMeasuredHeight(); if (returnedHeight >= maxHeight) { // We went over, figure out which height to return. If returnedHeight > // maxHeight, then the i'th position did not fit completely. return (disallowPartialChildPosition >= 0) // Disallowing is enabled (> -1) && (i > disallowPartialChildPosition) // We've past the min pos && (prevHeightWithoutPartialChild > 0) // We have a prev height && (returnedHeight != maxHeight) // i'th child did not fit completely ? prevHeightWithoutPartialChild : maxHeight; } if ((disallowPartialChildPosition >= 0) && (i >= disallowPartialChildPosition)) { prevHeightWithoutPartialChild = returnedHeight; } } // At this point, we went through the range of children, and they each // completely fit, so return the returnedHeight return returnedHeight; } protected void setSelectorEnabled(boolean enabled) { if (mSelector != null) { mSelector.setEnabled(enabled); } } private static class GateKeeperDrawable extends DrawableWrapper { private boolean mEnabled; public GateKeeperDrawable(Drawable drawable) { super(drawable); mEnabled = true; } void setEnabled(boolean enabled) { mEnabled = enabled; } @Override public boolean setState(int[] stateSet) { if (mEnabled) { return super.setState(stateSet); } return false; } @Override public void draw(Canvas canvas) { if (mEnabled) { super.draw(canvas); } } @Override public void setHotspot(float x, float y) { if (mEnabled) { super.setHotspot(x, y); } } @Override public void setHotspotBounds(int left, int top, int right, int bottom) { if (mEnabled) { super.setHotspotBounds(left, top, right, bottom); } } @Override public boolean setVisible(boolean visible, boolean restart) { if (mEnabled) { return super.setVisible(visible, restart); } return false; } } }