Android自定义Seekbar滑动条，Pop提示跟随滑动按钮一起滑动

由于项目需要做出此效果，自定义写了一个。

效果图

思路：

原始的seekbar只有滑动条并没有下方的提示文字，所以我们必须要继承Seekbar重写这个控件。

代码：

在values文件夹下新建attrs.xml,用于设置跟随滑动按钮的文字大小，颜色，背景。

<declare-styleable name="MySeekBar">
        <attr name="textsize" format="dimension" />
        <attr name="textcolor" format="color" />
        <attr name="img" format="reference" />
</declare-styleable>
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在布局里引用此控件

 <com.jzh.myseekbar.MySeekBar
            android:id="@+id/seekBar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:max="80"
            android:maxHeight="10dp"
            android:progress="0"
            android:progressDrawable="@drawable/seekbar_style"
            android:splitTrack="false"
            android:thumb="@mipmap/niu"
            app:img="@mipmap/ann"
            app:textcolor="#fff"
            app:textsize="14dp" />
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自定义控件样式

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@android:id/background">

        <shape>
            <corners android:radius="5dp" />
            <gradient
                android:angle="0"
                android:centerColor="@android:color/holo_orange_dark"
                android:endColor="@android:color/holo_red_dark"
                android:startColor="#2aade3" />
        </shape>
    </item>

</layer-list>
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主要核心代码

/**
     * 文本的颜色
     */
    private int mTitleTextColor;
    /**
     * 文本的大小
     */
    private float mTitleTextSize;
    private String mTitleText;//文字的内容

    /**
     * 背景图片
     */
    private int img;
    private Bitmap map;
    //bitmap对应的宽高
    private float img_width, img_height;
    Paint paint;

    private float numTextWidth;
    //测量seekbar的规格
    private Rect rect_seek;
    private Paint.FontMetrics fm;

    public static final int TEXT_ALIGN_LEFT = 0x00000001;
    public static final int TEXT_ALIGN_RIGHT = 0x00000010;
    public static final int TEXT_ALIGN_CENTER_VERTICAL = 0x00000100;
    public static final int TEXT_ALIGN_CENTER_HORIZONTAL = 0x00001000;
    public static final int TEXT_ALIGN_TOP = 0x00010000;
    public static final int TEXT_ALIGN_BOTTOM = 0x00100000;
    /**
     * 文本中轴线X坐标
     */
    private float textCenterX;
    /**
     * 文本baseline线Y坐标
     */
    private float textBaselineY;
    /**
     * 文字的方位
     */
    private int textAlign;

    public MySeekBar(Context context) {
        this(context, null);
    }

    public MySeekBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MySeekBar(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray array = context.getTheme().obtainStyledAttributes(attrs, R.styleable.MySeekBar, defStyleAttr, 0);
        int n = array.getIndexCount();
        for (int i = 0; i < n; i++) {
            int attr = array.getIndex(i);
            switch (attr) {
                case R.styleable.MySeekBar_textsize:
                    mTitleTextSize = array.getDimension(attr, 15f);
                    break;
                case R.styleable.MySeekBar_textcolor:
                    mTitleTextColor = array.getColor(attr, Color.WHITE);
                    break;
                case R.styleable.MySeekBar_img:
                    img = array.getResourceId(attr, R.mipmap.ic_launcher);
                    break;
            }
        }
        array.recycle();
        getImgWH();
        paint = new Paint();
        paint.setAntiAlias(true);//设置抗锯齿
        paint.setTextSize(mTitleTextSize);//设置文字大小
        paint.setColor(mTitleTextColor);//设置文字颜色
        //设置控件的padding 给提示文字留出位置
        setPadding((int) Math.ceil(img_width) / 2, 0, (int) Math.ceil(img_height) / 2, (int) Math.ceil(img_height) + 10);
        textAlign = TEXT_ALIGN_CENTER_HORIZONTAL | TEXT_ALIGN_CENTER_VERTICAL;
    }

    /**
     * 获取图片的宽高
     */
    private void getImgWH() {
        map = BitmapFactory.decodeResource(getResources(), img);
        img_width = map.getWidth();
        img_height = map.getHeight();

    }

    @Override
    protected synchronized void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        setTextLocation();//定位文本绘制的位置
        rect_seek = this.getProgressDrawable().getBounds();
        //定位文字背景图片的位置
        float bm_x = rect_seek.width() * getProgress() / getMax();
        float bm_y = rect_seek.height() + 20;
//        //计算文字的中心位置在bitmap
        float text_x = rect_seek.width() * getProgress() / getMax() + (img_width - numTextWidth) / 2;
        canvas.drawBitmap(map, bm_x, bm_y, paint);//画背景图
        // canvas.drawRoundRect();
        canvas.drawText(mTitleText, text_x, (float) (textBaselineY + bm_y + (0.16 * img_height / 2)), paint);//画文字

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        invalidate();//监听手势滑动，不断重绘文字和背景图的显示位置
        return super.onTouchEvent(event);
    }

    /**
     * 定位文本绘制的位置
     */
    private void setTextLocation() {

        fm = paint.getFontMetrics();
        //文本的宽度
        mTitleText = getProgress() + 10 + "℃";

        numTextWidth = paint.measureText(mTitleText);

        float textCenterVerticalBaselineY = img_height / 2 - fm.descent + (fm.descent - fm.ascent) / 2;
        switch (textAlign) {
            case TEXT_ALIGN_CENTER_HORIZONTAL | TEXT_ALIGN_CENTER_VERTICAL:
                textCenterX = img_width / 2;
                textBaselineY = textCenterVerticalBaselineY;
                break;
            case TEXT_ALIGN_LEFT | TEXT_ALIGN_CENTER_VERTICAL:
                textCenterX = numTextWidth / 2;
                textBaselineY = textCenterVerticalBaselineY;
                break;
            case TEXT_ALIGN_RIGHT | TEXT_ALIGN_CENTER_VERTICAL:
                textCenterX = img_width - numTextWidth / 2;
                textBaselineY = textCenterVerticalBaselineY;
                break;
            case TEXT_ALIGN_BOTTOM | TEXT_ALIGN_CENTER_HORIZONTAL:
                textCenterX = img_width / 2;
                textBaselineY = img_height - fm.bottom;
                break;
            case TEXT_ALIGN_TOP | TEXT_ALIGN_CENTER_HORIZONTAL:
                textCenterX = img_width / 2;
                textBaselineY = -fm.ascent;
                break;
            case TEXT_ALIGN_TOP | TEXT_ALIGN_LEFT:
                textCenterX = numTextWidth / 2;
                textBaselineY = -fm.ascent;
                break;
            case TEXT_ALIGN_BOTTOM | TEXT_ALIGN_LEFT:
                textCenterX = numTextWidth / 2;
                textBaselineY = img_height - fm.bottom;
                break;
            case TEXT_ALIGN_TOP | TEXT_ALIGN_RIGHT:
                textCenterX = img_width - numTextWidth / 2;
                textBaselineY = -fm.ascent;
                break;
            case TEXT_ALIGN_BOTTOM | TEXT_ALIGN_RIGHT:
                textCenterX = img_width - numTextWidth / 2;
                textBaselineY = img_height - fm.bottom;
                break;
        }
    }