ListView 源码学习笔记 [ 原创 ]

ListView 源码学习笔记

public class ListView extends AbsListView {
    /**
     * Used to indicate a no preference for a position type.
　　　* 指示一个没有被引用的位置
     */
    static final int NO_POSITION = -1;

    /**
     * Normal list that does not indicate choices
　　　* 普通列表显示(没有指定显示模式)
     */

    public static final int CHOICE_MODE_NONE = 0;

    /**
     * The list allows up to one choice
　　　* 单选模式
     */
    public static final int CHOICE_MODE_SINGLE = 1;

    /**
     * The list allows multiple choices
　　　* 多选模式
     */
    public static final int CHOICE_MODE_MULTIPLE = 2;

    /**
     * When arrow scrolling, ListView will never scroll more than this factor times the height of the list.
     * 
     */
    private static final float MAX_SCROLL_FACTOR = 0.33f;

    /**
     * When arrow scrolling, need a certain amount of pixels to preview next items. This is usually the fading edge,
     * but if that is small enough, we want to make sure we preview at least this many pixels.
     * 
     */
    private static final int MIN_SCROLL_PREVIEW_PIXELS = 2;

还有一些用到的重要的类和方法

public void setSelection(int position)

public void setCacheColorHint(int color)

public void setChoiceMode(int choiceMode)

public boolean performItemClick(View view, int position, long id)

public void setItemChecked(int position, boolean value)

下面的 mIsCacheColorOpaque 是与背景透明色相关的东西.

private boolean mIsCacheColorOpaque;

@Override
public boolean isOpaque() {
　　return (mCachingStarted && mIsCacheColorOpaque && mDividerIsOpaque &&
　　　　hasOpaqueScrollbars()) || super.isOpaque();
}

@Override
public void setCacheColorHint(int color) {
　　final boolean opaque = (color >>> 24) == 0xFF;
　　mIsCacheColorOpaque = opaque;
　　if (opaque) {
　　　　if (mDividerPaint == null) {
　　　　　　mDividerPaint = new Paint();
　　　　}
　　　　mDividerPaint.setColor(color);
　　}
　　super.setCacheColorHint(color);
}

下面的

/**
 * SparseBooleanArrays map integers to booleans. Unlike a normal array of booleans there can be gaps in the indices.
 * It is intended to be more efficient than using a HashMap to map Integers to Booleans.
 * 对于从 Integer 到 Boolean 的映射, 使用 SparseBooleanArrays 比 HashMap 更有效率.
 */
private SparseBooleanArray mCheckStates;
private LongSparseArray<Boolean> mCheckedIdStates;

public void setChoiceMode(int choiceMode) {
　　mChoiceMode = choiceMode;
　　if (mChoiceMode != CHOICE_MODE_NONE) {
　　　　if (mCheckStates == null) {
　　　　　　mCheckStates = new SparseBooleanArray();
　　　　}
　　　　if (mCheckedIdStates == null && mAdapter != null && mAdapter.hasStableIds()) {
　　　　　　mCheckedIdStates = new LongSparseArray<Boolean>();
　　　　}
　　}
}