簡單分析一下listview右側(cè)快速拖動(dòng)條的實(shí)現(xiàn).
1 IndexScroller
首先實(shí)現(xiàn)一個(gè)IndexScroller類,這個(gè)類用于控制右側(cè)的快速拖動(dòng)條.
1.1 構(gòu)造方法:
public IndexScroller(Context context, ListView lv) {
mDensity = context.getResources().getDisplayMetrics().density;
mScaledDensity = context.getResources().getDisplayMetrics().scaledDensity;
mListView = lv;
setAdapter(mListView.getAdapter());
mIndexbarWidth = 20 * mDensity;
mIndexbarMargin = 10 * mDensity;
mPreviewPadding = 5 * mDensity;
}
構(gòu)造方法主要是設(shè)置高寬,綁定listview(需要實(shí)現(xiàn)SectionIndexer接口)和adapter.
1.2 攔截觸摸事件:
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
// If down event occurs inside index bar region, start indexing
if (mState != STATE_HIDDEN && contains(ev.getX(), ev.getY())) {
setState(STATE_SHOWN);
// It demonstrates that the motion event started from index bar
mIsIndexing = true;
// Determine which section the point is in, and move the list to that section
mCurrentSection = getSectionByPoint(ev.getY());
mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
return true;
}
break;
case MotionEvent.ACTION_MOVE:
if (mIsIndexing) {
// If this event moves inside index bar
if (contains(ev.getX(), ev.getY())) {
// Determine which section the point is in, and move the list to that section
mCurrentSection = getSectionByPoint(ev.getY());
mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
}
return true;
}
break;
case MotionEvent.ACTION_UP:
if (mIsIndexing) {
mIsIndexing = false;
mCurrentSection = -1;
}
if (mState == STATE_SHOWN)
setState(STATE_HIDING);
break;
}
return false;
}
當(dāng)檢測到按下和移動(dòng)時(shí),根據(jù)位置獲取當(dāng)前按下的Section,然后調(diào)用SectionIndexer的方法獲取對應(yīng)的Listv的位置,然后設(shè)置listeview 的setSelection.
當(dāng)松開時(shí),隱藏listview.
1.3 繪制
繪制主要使用Paint在Canvas上繪制右側(cè)圖形,其實(shí)本身并不復(fù)雜,不再詳述.
public void draw(Canvas canvas) {
if (mState == STATE_HIDDEN)
return;
// mAlphaRate determines the rate of opacity
Paint indexbarPaint = new Paint();
indexbarPaint.setColor(Color.BLACK);
indexbarPaint.setAlpha((int) (64 * mAlphaRate));
indexbarPaint.setAntiAlias(true);
canvas.drawRoundRect(mIndexbarRect, 5 * mDensity, 5 * mDensity, indexbarPaint);
if (mSections != null && mSections.length > 0) {
// Preview is shown when mCurrentSection is set
if (mCurrentSection >= 0) {
Paint previewPaint = new Paint();
previewPaint.setColor(Color.BLACK);
previewPaint.setAlpha(96);
previewPaint.setAntiAlias(true);
previewPaint.setShadowLayer(3, 0, 0, Color.argb(64, 0, 0, 0));
Paint previewTextPaint = new Paint();
previewTextPaint.setColor(Color.WHITE);
previewTextPaint.setAntiAlias(true);
previewTextPaint.setTextSize(50 * mScaledDensity);
float previewTextWidth = previewTextPaint.measureText(mSections[mCurrentSection]);
float previewSize = 2 * mPreviewPadding + previewTextPaint.descent() - previewTextPaint.ascent();
RectF previewRect = new RectF((mListViewWidth - previewSize) / 2
, (mListViewHeight - previewSize) / 2
, (mListViewWidth - previewSize) / 2 + previewSize
, (mListViewHeight - previewSize) / 2 + previewSize);
canvas.drawRoundRect(previewRect, 5 * mDensity, 5 * mDensity, previewPaint);
canvas.drawText(mSections[mCurrentSection], previewRect.left + (previewSize - previewTextWidth) / 2 - 1
, previewRect.top + mPreviewPadding - previewTextPaint.ascent() + 1, previewTextPaint);
}
Paint indexPaint = new Paint();
indexPaint.setColor(Color.WHITE);
indexPaint.setAlpha((int) (255 * mAlphaRate));
indexPaint.setAntiAlias(true);
indexPaint.setTextSize(12 * mScaledDensity);
float sectionHeight = (mIndexbarRect.height() - 2 * mIndexbarMargin) / mSections.length;
float paddingTop = (sectionHeight - (indexPaint.descent() - indexPaint.ascent())) / 2;
for (int i = 0; i < mSections.length; i++) {
float paddingLeft = (mIndexbarWidth - indexPaint.measureText(mSections[i])) / 2;
if (mCurrentSection==i) {
Paint selectPaint = new Paint();
selectPaint.setColor(Color.GREEN);
selectPaint.setAlpha((int) (255 * mAlphaRate));
selectPaint.setAntiAlias(true);
selectPaint.setTextSize(12 * mScaledDensity);
canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft
, mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - selectPaint.ascent(), selectPaint);
}else {
canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft
, mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - indexPaint.ascent(), indexPaint);
}
}
}
}
至此,IndexScroller的工作已經(jīng)完成.
2 IndexableListView
我們注意到上面的IndexScroller其實(shí)只是一個(gè)普通類,所以里面的draw 攔截按鍵等方法并不會被真正被調(diào)用,所以我們需要在IndexableListView中調(diào)用這些方法.
IndexableListView是一個(gè)繼承自ListView的類,首先通過setFastScrollEnabled方法來創(chuàng)建IndexScroller對象.
public void setFastScrollEnabled(boolean enabled) {
mIsFastScrollEnabled = enabled;
if (mIsFastScrollEnabled) {
if (mScroller == null)
mScroller = new IndexScroller(getContext(), this);
} else {
if (mScroller != null) {
mScroller.hide();
mScroller = null;
}
}
}
重寫draw方法,調(diào)用IndexScroller的draw方法:
public void draw(Canvas canvas) {
super.draw(canvas);
// Overlay index bar
if (mScroller != null)
mScroller.draw(canvas);
}
重寫onInterceptTouchEvent方法,判斷如果觸摸位置在IndexScroller范圍內(nèi),則攔截事件:
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if(mScroller.contains(ev.getX(), ev.getY()))
return true;
return super.onInterceptTouchEvent(ev);
}
重寫onTouchEvent方法:
public boolean onTouchEvent(MotionEvent ev) {
// Intercept ListView's touch event
if (mScroller != null && mScroller.onTouchEvent(ev))
return true;
if (mGestureDetector == null) {
mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
// If fling happens, index bar shows
if (mScroller != null)
mScroller.show();
return super.onFling(e1, e2, velocityX, velocityY);
}
});
}
mGestureDetector.onTouchEvent(ev);
return super.onTouchEvent(ev);
}
主要是兩個(gè)作用,一個(gè)是當(dāng)IndexScroller存在時(shí)攔截按鍵事件處理,另一個(gè)就是在mScroller 不可見時(shí),將mScroller 置為可見.
下面附上兩個(gè)類的全部代碼:
IndexableListView主要實(shí)現(xiàn)代碼在以下兩個(gè)類:
public class IndexableListView extends ListView {
private boolean mIsFastScrollEnabled = false;
private IndexScroller mScroller = null;
private GestureDetector mGestureDetector = null;
public IndexableListView(Context context) {
super(context);
}
public IndexableListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public IndexableListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
public boolean isFastScrollEnabled() {
return mIsFastScrollEnabled;
}
@Override
public void setFastScrollEnabled(boolean enabled) {
mIsFastScrollEnabled = enabled;
if (mIsFastScrollEnabled) {
if (mScroller == null)
mScroller = new IndexScroller(getContext(), this);
} else {
if (mScroller != null) {
mScroller.hide();
mScroller = null;
}
}
}
@Override
public void draw(Canvas canvas) {
super.draw(canvas);
// Overlay index bar
if (mScroller != null)
mScroller.draw(canvas);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
// Intercept ListView's touch event
if (mScroller != null && mScroller.onTouchEvent(ev))
return true;
if (mGestureDetector == null) {
mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
// If fling happens, index bar shows
if (mScroller != null)
mScroller.show();
return super.onFling(e1, e2, velocityX, velocityY);
}
});
}
mGestureDetector.onTouchEvent(ev);
return super.onTouchEvent(ev);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if(mScroller.contains(ev.getX(), ev.getY()))
return true;
return super.onInterceptTouchEvent(ev);
}
@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);
if (mScroller != null)
mScroller.setAdapter(adapter);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (mScroller != null)
mScroller.onSizeChanged(w, h, oldw, oldh);
}
}
還有一個(gè)IndexScroller:
public class IndexScroller {
private float mIndexbarWidth;
private float mIndexbarMargin;
private float mPreviewPadding;
private float mDensity;
private float mScaledDensity;
private float mAlphaRate;
private int mState = STATE_HIDDEN;
private int mListViewWidth;
private int mListViewHeight;
private int mCurrentSection = -1;
private boolean mIsIndexing = false;
private ListView mListView = null;
private SectionIndexer mIndexer = null;
private String[] mSections = null;
private RectF mIndexbarRect;
private static final int STATE_HIDDEN = 0;
private static final int STATE_SHOWING = 1;
private static final int STATE_SHOWN = 2;
private static final int STATE_HIDING = 3;
public IndexScroller(Context context, ListView lv) {
mDensity = context.getResources().getDisplayMetrics().density;
mScaledDensity = context.getResources().getDisplayMetrics().scaledDensity;
mListView = lv;
setAdapter(mListView.getAdapter());
mIndexbarWidth = 20 * mDensity;
mIndexbarMargin = 10 * mDensity;
mPreviewPadding = 5 * mDensity;
}
public void draw(Canvas canvas) {
if (mState == STATE_HIDDEN)
return;
// mAlphaRate determines the rate of opacity
Paint indexbarPaint = new Paint();
indexbarPaint.setColor(Color.BLACK);
indexbarPaint.setAlpha((int) (64 * mAlphaRate));
indexbarPaint.setAntiAlias(true);
canvas.drawRoundRect(mIndexbarRect, 5 * mDensity, 5 * mDensity, indexbarPaint);
if (mSections != null && mSections.length > 0) {
// Preview is shown when mCurrentSection is set
if (mCurrentSection >= 0) {
Paint previewPaint = new Paint();
previewPaint.setColor(Color.BLACK);
previewPaint.setAlpha(96);
previewPaint.setAntiAlias(true);
previewPaint.setShadowLayer(3, 0, 0, Color.argb(64, 0, 0, 0));
Paint previewTextPaint = new Paint();
previewTextPaint.setColor(Color.WHITE);
previewTextPaint.setAntiAlias(true);
previewTextPaint.setTextSize(50 * mScaledDensity);
float previewTextWidth = previewTextPaint.measureText(mSections[mCurrentSection]);
float previewSize = 2 * mPreviewPadding + previewTextPaint.descent() - previewTextPaint.ascent();
RectF previewRect = new RectF((mListViewWidth - previewSize) / 2
, (mListViewHeight - previewSize) / 2
, (mListViewWidth - previewSize) / 2 + previewSize
, (mListViewHeight - previewSize) / 2 + previewSize);
canvas.drawRoundRect(previewRect, 5 * mDensity, 5 * mDensity, previewPaint);
canvas.drawText(mSections[mCurrentSection], previewRect.left + (previewSize - previewTextWidth) / 2 - 1
, previewRect.top + mPreviewPadding - previewTextPaint.ascent() + 1, previewTextPaint);
}
Paint indexPaint = new Paint();
indexPaint.setColor(Color.WHITE);
indexPaint.setAlpha((int) (255 * mAlphaRate));
indexPaint.setAntiAlias(true);
indexPaint.setTextSize(12 * mScaledDensity);
float sectionHeight = (mIndexbarRect.height() - 2 * mIndexbarMargin) / mSections.length;
float paddingTop = (sectionHeight - (indexPaint.descent() - indexPaint.ascent())) / 2;
for (int i = 0; i < mSections.length; i++) {
float paddingLeft = (mIndexbarWidth - indexPaint.measureText(mSections[i])) / 2;
if (mCurrentSection==i) {
Paint selectPaint = new Paint();
selectPaint.setColor(Color.GREEN);
selectPaint.setAlpha((int) (255 * mAlphaRate));
selectPaint.setAntiAlias(true);
selectPaint.setTextSize(12 * mScaledDensity);
canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft
, mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - selectPaint.ascent(), selectPaint);
}else {
canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft
, mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - indexPaint.ascent(), indexPaint);
}
}
}
}
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
// If down event occurs inside index bar region, start indexing
if (mState != STATE_HIDDEN && contains(ev.getX(), ev.getY())) {
setState(STATE_SHOWN);
// It demonstrates that the motion event started from index bar
mIsIndexing = true;
// Determine which section the point is in, and move the list to that section
mCurrentSection = getSectionByPoint(ev.getY());
mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
return true;
}
break;
case MotionEvent.ACTION_MOVE:
if (mIsIndexing) {
// If this event moves inside index bar
if (contains(ev.getX(), ev.getY())) {
// Determine which section the point is in, and move the list to that section
mCurrentSection = getSectionByPoint(ev.getY());
mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
}
return true;
}
break;
case MotionEvent.ACTION_UP:
if (mIsIndexing) {
mIsIndexing = false;
mCurrentSection = -1;
}
if (mState == STATE_SHOWN)
setState(STATE_HIDING);
break;
}
return false;
}
public void onSizeChanged(int w, int h, int oldw, int oldh) {
mListViewWidth = w;
mListViewHeight = h;
mIndexbarRect = new RectF(w - mIndexbarMargin - mIndexbarWidth
, mIndexbarMargin
, w - mIndexbarMargin
, h - mIndexbarMargin);
}
public void show() {
if (mState == STATE_HIDDEN)
setState(STATE_SHOWING);
else if (mState == STATE_HIDING)
setState(STATE_HIDING);
}
public void hide() {
if (mState == STATE_SHOWN)
setState(STATE_HIDING);
}
public void setAdapter(Adapter adapter) {
if (adapter instanceof SectionIndexer) {
mIndexer = (SectionIndexer) adapter;
mSections = (String[]) mIndexer.getSections();
}
}
private void setState(int state) {
if (state < STATE_HIDDEN || state > STATE_HIDING)
return;
mState = state;
switch (mState) {
case STATE_HIDDEN:
// Cancel any fade effect
mHandler.removeMessages(0);
break;
case STATE_SHOWING:
// Start to fade in
mAlphaRate = 0;
fade(0);
break;
case STATE_SHOWN:
// Cancel any fade effect
mHandler.removeMessages(0);
break;
case STATE_HIDING:
// Start to fade out after three seconds
mAlphaRate = 1;
fade(3000);
break;
}
}
public boolean contains(float x, float y) {
// Determine if the point is in index bar region, which includes the right margin of the bar
return (x >= mIndexbarRect.left && y >= mIndexbarRect.top && y <= mIndexbarRect.top + mIndexbarRect.height());
}
private int getSectionByPoint(float y) {
if (mSections == null || mSections.length == 0)
return 0;
if (y < mIndexbarRect.top + mIndexbarMargin)
return 0;
if (y >= mIndexbarRect.top + mIndexbarRect.height() - mIndexbarMargin)
return mSections.length - 1;
return (int) ((y - mIndexbarRect.top - mIndexbarMargin) / ((mIndexbarRect.height() - 2 * mIndexbarMargin) / mSections.length));
}
private void fade(long delay) {
mHandler.removeMessages(0);
mHandler.sendEmptyMessageAtTime(0, SystemClock.uptimeMillis() + delay);
}
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (mState) {
case STATE_SHOWING:
// Fade in effect
mAlphaRate += (1 - mAlphaRate) * 0.2;
if (mAlphaRate > 0.9) {
mAlphaRate = 1;
setState(STATE_SHOWN);
}
mListView.invalidate();
fade(10);
break;
case STATE_SHOWN:
// If no action, hide automatically
setState(STATE_HIDING);
break;
case STATE_HIDING:
// Fade out effect
mAlphaRate -= mAlphaRate * 0.2;
if (mAlphaRate < 0.1) {
mAlphaRate = 0;
setState(STATE_HIDDEN);
}
mListView.invalidate();
fade(10);
break;
}
}
};
}
