效果
實現邏輯
- 明確需求
字母導航欄在實際開發中還是比較多見的,城市選擇、名稱選擇等等可能需要到。 現在要做到的就是在滑動控件過程中可以有內容以及 下標的回調,方便處理其他邏輯!
- 整理思路
1、確定控件的尺寸,防止內容顯示不全。相關的邏輯在onMeasure()
方法中處理;
2、繪製顯示的內容,在按下和擡起不同狀態下文字、背景的顏色。相關邏輯在onDraw()
方法中;
3、滑動事件的處理以及事件回調。相關邏輯在onTouchEvent()方法中;
- 動手實現
在需求明確、思路清晰的情況下就要開始動手實現(需要了解自定義View的一些基礎API)。核心代碼就onDraw()中。在代碼中有思路和註釋,可以結合代碼一起看看。如果有疑惑、優化、錯誤的地方請在評論區提出,共同進步!
完整代碼
/**
* 自定義字母導航欄
*
* 總的來說就四步
* 1、測量控件尺寸{@link #onMeasure(int, int)}
* 2、繪製顯示內容(背景以及字符){@link #onDraw(Canvas)}
* 3、處理滑動事件{@link #onTouchEvent(MotionEvent)}
* 4、暴露接口{@link #setOnNavigationScrollerListener(OnNavigationScrollerListener)}
*
* @attr customTextColorDefault //導航欄默認文字顏色
* @attr customTextColorDown //導航欄按下文字顏色
* @attr customBackgroundColorDown //導航欄按下背景顏色
* @attr customLetterDivHeight //導航欄內容高度間隔
* @attr customTextSize //導航欄文字尺寸
* @attr customBackgroundAngle //導航欄背景角度
*/
public class CustomLetterNavigationView extends View {
private static final String TAG = "CustomLetterNavigation";
//導航內容
private String[] mNavigationContent;
//導航欄內容間隔
private float mContentDiv;
//導航欄文字大小
private float mContentTextSize;
//導航欄文字顏色
private int mContentTextColor;
//導航欄按下時背景顏色
private int mBackgroundColor;
//導航欄按下時圓角度數
private int mBackGroundAngle = 0;
//導航欄按下時文字顏色
private int mDownContentTextColor;
private TextPaint mTextPaint;
private Paint mPaintBackgrount;
private boolean mEventActionState = false;
private String mCurrentLetter = "";
private OnNavigationScrollerListener mOnNavigationScrollerListener;
private final RectF mRectF = new RectF();
public CustomLetterNavigationView(Context context) {
this(context, null);
}
public CustomLetterNavigationView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public CustomLetterNavigationView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initDefaultData();//初始化默認數據
initAttrs(context, attrs);
}
@Override
protected void onDraw(Canvas canvas) {
/**
* <P>
* 這裏我們分爲兩步
*
* 1、繪製背景
* 這裏簡單,直接調用Canvas的drawRoundRect()方法直接繪製
* 2、繪製顯示文本
* 繪製文字首先要定位,定位每個字符的座標
* X軸簡單,寬度的一半
* Y軸座標通過每個字符的高heightShould乘以已繪製字符的數目
* </P>
*/
int mViewWidth = getWidth();
//繪製背景
mRectF.set(0, 0, mViewWidth, getHeight());
if (mEventActionState) {
mTextPaint.setColor(mDownContentTextColor);
mPaintBackgrount.setColor(mBackgroundColor);
canvas.drawRoundRect(mRectF, mBackGroundAngle, mBackGroundAngle, mPaintBackgrount);
} else {
mTextPaint.setColor(mContentTextColor);
mPaintBackgrount.setColor(Color.TRANSPARENT);
Drawable mBackground = getBackground();
if (mBackground instanceof ColorDrawable) {
mPaintBackgrount.setColor(((ColorDrawable) mBackground).getColor());
}
canvas.drawRoundRect(mRectF, mBackGroundAngle, mBackGroundAngle, mPaintBackgrount);
}
//繪製文本
float textX = mViewWidth / 2;
//X軸座標
int contentLenght = getContentLength();
//Y軸座標(這裏在測量的時候多加入了兩個間隔高度要減去,同時還有Padding值)
float heightShould = (getHeight() - mContentDiv * 2 - getPaddingTop() - getPaddingBottom()) / contentLenght;
for (int i = 0; i < contentLenght; i++) {
//計算Y軸的座標
float startY = ((i + 1) * heightShould) + getPaddingTop();
//繪製文字
canvas.drawText(mNavigationContent[i], textX, startY, mTextPaint);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
/**
* 這裏主要處理手指滑動事件
*/
float mEventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
//手指按下的時候,修改Enent狀態、重繪背景、觸發回調
mEventActionState = true;
invalidate();
if (mOnNavigationScrollerListener != null) {
mOnNavigationScrollerListener.onDown();
}
scrollCount(mEventY);
break;
case MotionEvent.ACTION_MOVE:
scrollCount(mEventY);
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
//手指離開的時候,修改Enent狀態、重繪背景、觸發回調
mEventActionState = false;
invalidate();
if (mOnNavigationScrollerListener != null) {
mOnNavigationScrollerListener.onUp();
}
break;
}
return true;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
/**
* <p>
* 這裏做了簡單的適應,其目的就是爲了能夠正常的顯示我們的內容
*
* 不管設置的是真實尺寸或者是包裹內容,都會以內容的最小尺寸爲
* 基礎,如果設置的控件尺寸大於我們內容的最小尺寸,就使用控件
* 尺寸,反之使用內容的最小尺寸!
* </p>
*/
int widhtMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
//獲取控件的尺寸
int actualWidth = MeasureSpec.getSize(widthMeasureSpec);
int actualHeight = MeasureSpec.getSize(heightMeasureSpec);
int contentLegth = getContentLength();
//計算一個文字的尺寸
Rect mRect = measureTextSize();
//內容的最小寬度
float contentWidth = mRect.width() + mContentDiv * 2;
//內容的最小高度
float contentHeight = mRect.height() * contentLegth + mContentDiv * (contentLegth + 3);
if (MeasureSpec.AT_MOST == widhtMode) {
//寬度包裹內容
actualWidth = (int) contentWidth + getPaddingLeft() + getPaddingRight();
} else if (MeasureSpec.EXACTLY == widhtMode) {
//寬度限制
if (actualWidth < contentWidth) {
actualWidth = (int) contentWidth + getPaddingLeft() + getPaddingRight();
}
}
if (MeasureSpec.AT_MOST == heightMode) {
//高度包裹內容
actualHeight = (int) contentHeight + getPaddingTop() + getPaddingBottom();
} else if (MeasureSpec.EXACTLY == widhtMode) {
//高度限制
if (actualHeight < contentHeight) {
actualHeight = (int) contentHeight + getPaddingTop() + getPaddingBottom();
}
}
setMeasuredDimension(actualWidth, actualHeight);
}
/**
* 初始化默認數據
*/
private void initDefaultData() {
mNavigationContent = new String[]{"搜", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"};
mContentDiv = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 5, getResources().getDisplayMetrics());
mContentTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 14, getResources().getDisplayMetrics());
mContentTextColor = Color.parseColor("#333333");
mDownContentTextColor = Color.WHITE;
mBackgroundColor = Color.parseColor("#d7d7d7");
mBackGroundAngle = 0;
//繪製文字畫筆
mTextPaint = new TextPaint();
mTextPaint.setAntiAlias(true);
mTextPaint.setTextSize(mContentTextSize);
mTextPaint.setColor(mContentTextColor);
mTextPaint.setTextAlign(Paint.Align.CENTER);
//繪製背景畫筆
mPaintBackgrount = new Paint();
mPaintBackgrount.setAntiAlias(true);
mPaintBackgrount.setStyle(Paint.Style.FILL);
}
/**
* 初始化自定義屬性
*
* @param context
* @param attrs
*/
private void initAttrs(Context context, AttributeSet attrs) {
TypedArray mTypedArray = context.obtainStyledAttributes(attrs, R.styleable.CustomLetterNavigationView);
mContentTextColor = mTypedArray.getColor(R.styleable.CustomLetterNavigationView_customTextColorDefault, mContentTextColor);
mBackgroundColor = mTypedArray.getColor(R.styleable.CustomLetterNavigationView_customBackgroundColorDown, mBackgroundColor);
mDownContentTextColor = mTypedArray.getColor(R.styleable.CustomLetterNavigationView_customTextColorDown, mDownContentTextColor);
mContentTextSize = mTypedArray.getDimension(R.styleable.CustomLetterNavigationView_customTextSize, mContentTextSize);
mContentDiv = mTypedArray.getFloat(R.styleable.CustomLetterNavigationView_customLetterDivHeight, mContentDiv);
mBackGroundAngle = mTypedArray.getInt(R.styleable.CustomLetterNavigationView_customBackgroundAngle, mBackGroundAngle);
mTypedArray.recycle();
}
/**
* 獲取內容長度
*
* @return 內容長度
*/
private int getContentLength() {
if (mNavigationContent != null) {
return mNavigationContent.length;
}
return 0;
}
/**
* 滑動計算
*
* @param mEventY Y軸滑動距離
*/
private void scrollCount(float mEventY) {
//滑動的時候利用滑動距離和每一個字符高度進行取整,獲取到Index
Rect mRect = measureTextSize();
int index = (int) ((mEventY - getPaddingTop() - getPaddingBottom() - mContentDiv * 2) / (mRect.height() + mContentDiv));
//防止越界
if (index >= 0 && index < getContentLength()) {
String newLetter = mNavigationContent[index];
//防止重複觸發回調
if (!mCurrentLetter.equals(newLetter)) {
mCurrentLetter = newLetter;
if (mOnNavigationScrollerListener != null) {
mOnNavigationScrollerListener.onScroll(mCurrentLetter, index);
}
}
}
}
/**
* 測量文字的尺寸
*
* @return 一個漢字的矩陣
*/
public Rect measureTextSize() {
Rect mRect = new Rect();
if (mTextPaint != null) {
mTextPaint.getTextBounds("田", 0, 1, mRect);
}
return mRect;
}
/**
* 設置導航欄滑動監聽
*
* @param onNavigationScrollerListener
*/
public void setOnNavigationScrollerListener(OnNavigationScrollerListener onNavigationScrollerListener) {
this.mOnNavigationScrollerListener = onNavigationScrollerListener;
}
/**
* 設置導航欄顯示內容
*
* @param content 需要顯示的內容
*/
public void setNavigationContent(String content) {
if (!TextUtils.isEmpty(content)) {
mNavigationContent = null;
mNavigationContent = new String[content.length()];
for (int i = 0; i < content.length(); i++) {
mNavigationContent[i] = String.valueOf(content.charAt(i));
}
}
//需要重新測量
requestLayout();
}
public interface OnNavigationScrollerListener {
//按下
void onDown();
//滑動
void onScroll(String letter, int position);
//離開
void onUp();
}
}
<declare-styleable name="CustomLetterNavigationView">
<attr name="customTextColorDefault" format="color" />
<attr name="customTextColorDown" format="color" />
<attr name="customBackgroundColorDown" format="color" />
<attr name="customLetterDivHeight" format="dimension" />
<attr name="customTextSize" format="dimension" />
<attr name="customBackgroundAngle" format="integer" />
</declare-styleable>