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Question

我想创建一个带有以下文本的自定义 SeekBar，该文本会根据拇指的位置更新其位置（和进度）。

我需要达到什么目标：

假设：

1. 最小值 = 1000
2. 最大值 = 30000

案例 1： 进度为 0%（或最小值 = 1000），文本应与拇指左边框对齐。

案例 2： 进度文本显示在 Thumb drawable 上方并居中，因为它有空间来绘制自己。

案例 3： 进度为 100%（或最大值 = 3000），文本应与 Thumb 的右边框对齐。

我已经拥有了什么：

public class CustomSeekBar extends SeekBar {
    private Paint paint;
    private int[] coordCenterTemp = new int[]{0, 0};

    // .....

private void init() {
    paint = new Paint();
    paint.setColor(Color.BLACK);
    paint.setStyle(Paint.Style.STROKE);
    paint.setTextSize(sp2px(20));
    paint.setTextAlign(Paint.Align.CENTER);
}

private int sp2px(int sp) {
    return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp, getResources().getDisplayMetrics());
}

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

    String str = String.valueOf(getProgress());

    int thumb_x = (int) (( (double)this.getProgress()/this.getMax() ) * (double)(this.getWidth()));
    int thumb_y = 30;

    int textMeasure = (int) paint.measureText(str, 0, str.length());

    if ((textMeasure / 2) + thumb_x <= getRight()) {
        coordCenterTemp[0] = thumb_x;
        coordCenterTemp[1] = thumb_y;
    }
    canvas.drawText(str, coordCenterTemp[0], coordCenterTemp[1], paint);
}
}

这适用于进度为 50% 时。一旦我向右或向左滑动，文本就会被绘制到错误的方向。

我怎样才能做到这一点？

Answer 1

我最近实现了这样一个功能，这是我的代码：

首先定义一个 ThumbTextView，它位于您的TextView 上方的Seekbar：

public class ThumbTextView extends TextView {

    private LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    private int width = 0;

    public ThumbTextView(Context context) {
        super(context);
    }

    public ThumbTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public void attachToSeekBar(SeekBar seekBar) {
        String content = getText().toString();
        if (TextUtils.isEmpty(content) || seekBar == null)
            return;
        float contentWidth = this.getPaint().measureText(content);
        int realWidth = width - seekBar.getPaddingLeft() - seekBar.getPaddingRight();
        int maxLimit = (int) (width - contentWidth - seekBar.getPaddingRight());
        int minLimit = seekBar.getPaddingLeft();
        float percent = (float) (1.0 * seekBar.getProgress() / seekBar.getMax());
        int left = minLimit + (int) (realWidth * percent - contentWidth / 2.0);
        left = left <= minLimit ? minLimit : left >= maxLimit ? maxLimit : left;
        lp.setMargins(left, 0, 0, 0);
        setLayoutParams(lp);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (width == 0)
            width = MeasureSpec.getSize(widthMeasureSpec);
    }
}

然后定义您自己的 ThumbTextSeekBar 类，它是 Seekbar 和 ThumbSeekbar 的包装器：

public class ThumbTextSeekBar extends LinearLayout {

    public ThumbTextView tvThumb;
    public SeekBar seekBar;
    private SeekBar.OnSeekBarChangeListener onSeekBarChangeListener;

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

    public ThumbTextSeekBar(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        LayoutInflater.from(getContext()).inflate(R.layout.view_thumb_text_seekbar, this);
        setOrientation(LinearLayout.VERTICAL);
        tvThumb = (ThumbTextView) findViewById(R.id.tvThumb);
        seekBar = (SeekBar) findViewById(R.id.sbProgress);
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                if (onSeekBarChangeListener != null)
                    onSeekBarChangeListener.onStopTrackingTouch(seekBar);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                if (onSeekBarChangeListener != null)
                    onSeekBarChangeListener.onStartTrackingTouch(seekBar);
            }

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if (onSeekBarChangeListener != null)
                    onSeekBarChangeListener.onProgressChanged(seekBar, progress, fromUser);
                tvThumb.attachToSeekBar(seekBar);
            }
        });

    }

    public void setOnSeekBarChangeListener(SeekBar.OnSeekBarChangeListener l) {
        this.onSeekBarChangeListener = l;
    }

    public void setThumbText(String text) {
        tvThumb.setText(text);
    }

    public void setProgress(int progress) {
        if (progress == seekBar.getProgress() && progress == 0) {
            seekBar.setProgress(1);
            seekBar.setProgress(0);
        } else {
            seekBar.setProgress(progress);
        }
    }
}

最后，以如下方式使用它：

thumbTextSeekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            
                thumbTextSeekbar.setThumbText(seekBar.getProgress()));

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                thumbTextSeekbar.showTxt();
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                thumbTextSeekbar.hideTxt();
            }
        });

为了确保一切都完整，这里是R.layout.view_thumb_text_seekbar：

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <xxx.ui.widget.ThumbTextView
        android:id="@+id/tvThumb"
        style="@style/Textview.White.MediumSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/round_rect_black_trans"
        android:padding="4dp"
        android:visibility="gone" />

    <SeekBar
        android:id="@+id/sbProgress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="-16dp"
        android:layout_marginRight="-16dp"
        android:layout_marginTop="5dp"
        android:minHeight="20dp" />

</merge>

输出：