Android 自定義View3

先看效果圖

上一篇自定義view2因為字數的原因沒顯示在首頁，貌似只能在我隨筆列表裡看，這次是第三篇，為了湊點字數，把關鍵的地方提出來看一下

1canvas.drawText 的參數是怎麼控制 文字的位置的

canvas.drawText(文字, x, y,paint); 

其中x預設應該是文字的左邊距，y所對應的水平線是文字的底， 而不是文字的中心點，這裡比較重要，顯然把我們把想要設置的中心點坐標x，y直接填進去 是不會得到我們想要的效果的

X軸怎麼設置文字以 x參數為中心點，主要靠paint設置一個參數

paint.setTextAlign(Paint.Align.CENTER); //這樣設置後x坐標點為文字的水平中心

Y軸怎麼設置文字以y參數為中心點，主要考計算， 假設高度100的控制項，怎麼把字寫到50的高度上， y這個參數大概約等於 50 + 文字大小 / 4 + 一點點（加不加都行，我上面的效果是沒加，文字有點靠上了）

2畫一個圓的方法

canvas.drawCircle(x, y, paind);

3直接看整體代碼吧，還是在上一篇的基礎上做的改動

public class AAAView extends View {

    private Paint paint;
    private Paint bluePaint;
    private Paint whitePaint;
    private Paint greenPaind;
    private Scroller scroller;
    private float moveX;//移動距離
    private float downX;//手指按下的位置
    private int r;//每個字的半徑
    private int d;//直徑
    private int h;//控制項高度
    private int textSize = 25;
    private int location;//手指按在哪個字上
    private int checked = 3;//選中變藍色
    private String[] week = new String[]{"一", "二", "三", "四", "五", "六", "日"};
    private Context context;


    public AAAView(Context context) {
        super(context);
        init(context);
    }

    public AAAView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public AAAView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    private void init(Context context) {

        paint = new Paint();
        bluePaint = new Paint();
        whitePaint = new Paint();
        greenPaind = new Paint();
        scroller = new Scroller(context);

        paint.setColor(Color.BLACK);
        paint.setAntiAlias(true);
        paint.setTextSize(textSize);
        paint.setTextAlign(Paint.Align.CENTER);

        bluePaint.setColor(Color.BLUE);
        bluePaint.setAntiAlias(true);
        bluePaint.setTextSize(textSize);
        bluePaint.setTextAlign(Paint.Align.CENTER);

        greenPaind.setColor(Color.GREEN);
        greenPaind.setAntiAlias(true);
        greenPaind.setTextSize(textSize);
        greenPaind.setTextAlign(Paint.Align.CENTER);

        whitePaint.setColor(Color.WHITE);
        whitePaint.setAntiAlias(true);
        whitePaint.setTextSize(textSize);
        whitePaint.setTextAlign(Paint.Align.CENTER);

        this.context = context;

    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        r = getWidth() / 14;
        d = 2 * r;
        h = getHeight();

        canvas.drawLine(0, h / 2, getWidth(), h / 2, paint);

        canvas.drawCircle(r + checked * d + moveX, h / 4 * 3, 25, greenPaind);

        for (int i = 0; i < 7; i++) {
            if (i == 5 || i == 6) {
                canvas.drawText(week[i], r + i * d, h / 4 + textSize / 2, bluePaint);

                canvas.drawText(i + "", r + i * d + moveX, h / 4 * 3 + textSize / 4, bluePaint);
            } else {

                canvas.drawText(week[i], r + i * d, h / 4 + textSize / 2, paint);

                canvas.drawText(i + "", r + i * d + moveX, h / 4 * 3 + textSize / 4, paint);
            }
        }

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                downX = event.getX();
                location = (int) Math.ceil(downX / d);
                return true;
            case MotionEvent.ACTION_MOVE:
                moveX = (int) (event.getX() - downX);
                invalidate();
                return true;
            case MotionEvent.ACTION_UP://每次抬起手勢後，要恢復初始狀態
                moveX = 0;
                invalidate();
                if (event.getX() < location * d && event.getX() > (location - 1) * d) {
                    Toast.makeText(context, "點擊了第" + location + "個字", Toast.LENGTH_LONG).show();
                    checked = location - 1;
                    invalidate();
                }
                return true;
        }
        return super.onTouchEvent(event);
    }
}

離做成一個日曆又近了一步，下一篇應該會寫流暢的滑動，現在最後複原的時候是直接複原，太生硬了，再往後就是填上真的日期，然後在完善一些邏輯就差不多搞定了。