通过移动滑块更改文本颜色

底线是你挂一个监听器SeekBar，监听值并手动将值转换为颜色。例如像这样：

SeekBar seekBar = findViewById(R.id.seekBar);
seekBar.setMax(256 * 7 - 1);

seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        if (fromUser){
            int r = 0;
            int g = 0;
            int b = 0;

            if (progress < 256){
                b = progress;
            } else if (progress < 256 * 2) {
                g = progress % 256;
                b = 256 - progress % 256;
            } else if (progress < 256 * 3) {
                g = 255;
                b = progress % 256;
            } else if (progress < 256 * 4) {
                r = progress % 256;
                g = 256 - progress % 256;
                b = 256 - progress % 256;
            } else if (progress < 256 * 5) {
                r = 255;
                g = 0;
                b = progress % 256;
            } else if (progress < 256 * 6) {
                r = 255;
                g = progress % 256;
                b = 256 - progress % 256;
            } else if (progress < 256 * 7) {
                r = 255;
                g = 255;
                b = progress % 256;
            }

            targetTextView.setTextColor(Color.argb(255, r, g, b));
        }
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {

    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {

    }
});

示例取自enSO。