Android_自定義雙向SeekBar

目標:雙向拖動的自定義View

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實現步驟

自定義屬性的抽取 view尺寸的計算 相關內容的繪制(文字,原點,背景進度條,當前進度條等等) 處理滑動事件

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大體思路分四部分;我們一步步來;簡單的就一部帶過了

自定義屬性獲取:

 public ATDragView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setBackgroundColor(ContextCompat.getColor(context, android.R.color.white));
        TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.ATDragView, defStyleAttr, R.style.def_dragview);
        int indexCount = typedArray.getIndexCount();
        for (int i = 0; i < indexCount; i++) {
            int attr = typedArray.getIndex(i);
            switch (attr) {
                case R.styleable.ATDragView_seek_bg_color:
                    seekBgColor = typedArray.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.ATDragView_seek_pb_color:
                    seekPbColor = typedArray.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.ATDragView_seek_ball_solid_color:
                    seekBallSolidColor = typedArray.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.ATDragView_seek_ball_stroke_color:
                    seekBallStrokeColor = typedArray.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.ATDragView_seek_text_color:
                    seekTextColor = typedArray.getColor(attr, Color.BLACK);
                    break;
                case R.styleable.ATDragView_seek_text_size:
                    seekTextSize = typedArray.getDimensionPixelSize(attr, 0);
                    break;
            }
        }
        typedArray.recycle();
        init();
    }

拿到我們設置的屬性後,初始化我們需要的工具,比如畫筆,等

    private void init() {
        currentMovingType = BallType.LEFT;
        seekTextPaint = creatPaint(seekTextColor, seekTextSize, Paint.Style.FILL, 0);
        seekBgPaint = creatPaint(seekBgColor, 0, Paint.Style.FILL, 0);
        seekBallPaint = creatPaint(seekBallSolidColor, 0, Paint.Style.FILL, 0);
        seekPbPaint = creatPaint(seekPbColor, 0, Paint.Style.FILL, 0);
        seekBallEndPaint = creatPaint(seekPbColor, 0, Paint.Style.FILL, 0);
        seekBallStrokePaint = creatPaint(seekBallStrokeColor, 0, Paint.Style.FILL, 0);
        seekBallStrokePaint.setShadowLayer(5, 2, 2, seekBallStrokeColor);
    }

確定自定義view尺寸

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int measureHeight;
        if (heightMode == MeasureSpec.AT_MOST || heightMode == MeasureSpec.UNSPECIFIED) {
            measureHeight = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, DEF_HEIGHT, getContext().getResources().getDisplayMetrics());
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(measureHeight, MeasureSpec.EXACTLY);
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

繪制相關的內容部分,
這裡我們分析效果圖發現,需要繪制五部分,兩個圓,兩個進度條一個 一堆文字,我們根據計算出來的view尺寸以及UI給的比例,即可繪制出來他們這個就是canvas的API使用

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawTexts(canvas);
        drawSeekBG(canvas);
        drawSeekPB(canvas);
        drawLeftCircle(canvas);
        drawRightCircle(canvas);
    }

具體的文字繪制,是根據外界傳入的數據來繪制的所以細節如下

  private void drawTexts(Canvas canvas) {
        if (null == data) return;
        int size = data.size();
        int unitWidth = getUnitWidth(size - 1);
        for (int i = 0; i < size; i++) {
            String tempDesc = data.get(i);
            float measureTextWidth = seekPbPaint.measureText(tempDesc);
            canvas.drawText(tempDesc, DEF_PADDING + unitWidth * i - measureTextWidth / 2, seekTextY, seekTextPaint);
        }
    }

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這個View的核心部分不是繪制,而是計算,描述下我們具體的確定位置的思路

根據外界傳入的數據集合平均分view的寬度,求得平均一份的寬度大小 然後循環數據集合根據平均一份的寬度,確定沒個文字所在的坐標值

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然後我們看下計算的代碼;

// 計算單位寬度,view寬度-內容的左右邊距以及圓球的半徑,自己體會下為什麼
   private int getUnitWidth(int count) {
        return (viewWidth - 2 * DEF_PADDING - 2 * seekBallRadio) / count;
    }

這個方法可以說是最重要的一個了,

//根據當前手指觸摸的x坐標計算,手指離開屏幕以後,應該停留到哪個位置,比如滑動到400到500之間但是不到600,我們不能讓他停留在半路上,讓他自動找回他停留的左邊,也就是GIF中的小小回彈效果
  private int getCurrentSeekX(int upX) {
        if (null == data) {
            return 0;
        }
        int unitWidth = getUnitWidth(data.size() - 1);
        return unitWidth * (upX / unitWidth);
    }

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核心的代碼全部完畢了,我們看下onTouch裡面的處理

 public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
            //記錄手指按下的坐標
                downX = (int) event.getX();
                // 根據當前坐標,確定要移動哪個球球,因為我們說了,我們這個是有兩個球的,唯一的一個技巧點就是這個地方,根據手指按下的坐標找到距離哪個球位置最近就移動哪個球,這裡注意下.
                currentMovingType = getMovingLeftOrRight(downX);
                if (BallType.LEFT == currentMovingType) {
                    leftSeekBallX = downX;
                } else if (BallType.RIGHT == currentMovingType) {
                    rightSeekBallX = downX;
                }
                seekPbRectF = new RectF(leftSeekBallX, viewHeight * SEEK_BG_SCALE, rightSeekBallX, viewHeight * SEEK_BG_SCALE + BG_HEIGHT);

                break;
            case MotionEvent.ACTION_MOVE:
            //移動的時候根據計算出來的位置以及方向改變兩個小球的位置以及舉行進度條的RectF的范圍
                int moveX = (int) event.getX();
                // 特殊情況處理,兩個球重合應該怎麼辦,
                if (leftSeekBallX == rightSeekBallX) {
                    if (moveX - downX > 0) {
                        currentMovingType = BallType.RIGHT;
                        rightSeekBallX = moveX;
                    } else {
                        currentMovingType = BallType.LEFT;
                        leftSeekBallX = moveX;
                    }
                } else {
                    if (BallType.LEFT == currentMovingType) {
                        leftSeekBallX = leftSeekBallX - rightSeekBallX >= 0 ? rightSeekBallX : moveX;
                    } else if (BallType.RIGHT == currentMovingType) {
                        rightSeekBallX = rightSeekBallX - leftSeekBallX <= 0 ? leftSeekBallX : moveX;
                    }
                }
                seekPbRectF = new RectF(leftSeekBallX, viewHeight * SEEK_BG_SCALE, rightSeekBallX, viewHeight * SEEK_BG_SCALE + BG_HEIGHT);
                break;
            case MotionEvent.ACTION_UP:
            // 手指離開的時候,確定返回給UI的數據集
                if (BallType.LEFT == currentMovingType) {
                    leftPosition = getDataPosition((int) event.getX());
                    leftSeekBallX = leftSeekBallX - rightSeekBallX >= 0 ? rightSeekBallX : getCurrentSeekX((int) event.getX()) + DEF_PADDING + seekBallRadio;
                } else if (BallType.RIGHT == currentMovingType) {
                    rightPosition = getDataPosition((int) event.getX());
                    rightSeekBallX = rightSeekBallX - leftSeekBallX <= 0 ? leftSeekBallX : getCurrentSeekX((int) event.getX()) + DEF_PADDING + seekBallRadio;
                }
                if (null != dragFinishedListener) {
                    dragFinishedListener.dragFinished(leftPosition, rightPosition);
                }
                break;
        }
// 邊界處理,確保左邊的球不會超過右邊的,右邊的不會超過左邊的
        if (BallType.LEFT == currentMovingType) {
            if (leftSeekBallX < seekBallRadio + DEF_PADDING) {
                leftSeekBallX = seekBallRadio + DEF_PADDING;
            }
            if (leftSeekBallX > viewWidth - seekBallRadio - DEF_PADDING) {
                leftSeekBallX = viewWidth - seekBallRadio - DEF_PADDING;
            }
        } else if (BallType.RIGHT == currentMovingType) {
            if (rightSeekBallX < seekBallRadio + DEF_PADDING) {
                rightSeekBallX = seekBallRadio + DEF_PADDING;
            }
            if (rightSeekBallX > viewWidth - seekBallRadio - DEF_PADDING) {
                rightSeekBallX = viewWidth - seekBallRadio - DEF_PADDING;
            }
        }
        seekPbRectF = new RectF(leftSeekBallX, viewHeight * SEEK_BG_SCALE, rightSeekBallX, viewHeight * SEEK_BG_SCALE + BG_HEIGHT);
        invalidate();
        return true;
    }

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大部分的核心的代碼就這麼多,然後剩下的view寫完了就該把回調借口透出給UI 完活了…..

public void setData(List data, OnDragFinishedListener dragFinishedListener) {
        this.dragFinishedListener = dragFinishedListener;
        this.data = data;
        leftPosition = 0;
        if (null != data && data.size() != 0) {
            rightPosition = data.size() - 1;
        }
    }

寫了這麼多重要的還是這個地方源代碼下載地址https://github.com/GuoFeilong/ATDragViewDemo