最有效的方式为动态文本颜色变化的TextView [英] Most efficient way for Dynamic Text Color Change in TextView
问题描述
我想换一个几遍课文部分颜色有计时器。
I want to change color of parts of a text several times with a timer.
最简单的方法是这样的:
Simplest way is this:
SpannableStringBuilder ssb = new SpannableStringBuilder(mainText);
ForegroundColorSpan span = new ForegroundColorSpan(Color.BLUE);
ssb.setSpan(span, start, end, 0);
tv.setText(ssb);
但是,如果我运行上面的code多次在第二,我真正改变的TextView
每次这样一个不必要的内存 - 全(大)文CPU负载将具体发生在低端设备。
But if I run the above code several times in a second, I actually change the whole (large) text of TextView
each time so a unwanted memory-CPU load will happen specifically on lower-end devices.
我如何能有一个跨度
在的TextView
,只修改跨度
启动和结束位置?
How can I have a single Span
on TextView
and only change the Span
start and end position?
它会在所有或完整的文本替换将发生在幕后工作?
Will it work at all or a full text replace will happen behind the scene?
我的文字是固定的,不会永远不会改变。
My text is fixed and won't change never.
推荐答案
无需调用解决方案范围的移动的setText
方法:
Solution for span movement without calling setText
method:
final TextView tv = new TextView(this);
tv.setTextSize(32);
setContentView(tv);
SpannableStringBuilder ssb = new SpannableStringBuilder("0123456789012345678901234567890123456789");
ssb.append(ssb).append(ssb);
tv.setText(ssb, BufferType.SPANNABLE);
final Spannable sp = (Spannable) tv.getText();
final ForegroundColorSpan span = new ForegroundColorSpan(0xffff0000);
Runnable action = new Runnable() {
@Override
public void run() {
sp.setSpan(span, start, start + 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
start++;
if (start <= sp.length() - 4) {
tv.postDelayed(this, 50);
}
}
};
tv.postDelayed(action, 1000);
解决方案动态颜色变化:
class HSVSpan extends CharacterStyle {
int color;
float[] hsv = {0, 1, 1};
@Override
public void updateDrawState(TextPaint tp) {
tp.setColor(color);
}
public void update() {
hsv[0] += 5;
hsv[0] %= 360;
color = Color.HSVToColor(hsv);
// Log.d(TAG, "update " + Integer.toHexString(color));
}
}
和测试code:
final TextView tv = new TextView(this);
setContentView(tv);
SpannableStringBuilder ssb = new SpannableStringBuilder("0123456789");
final HSVSpan span = new HSVSpan();
ssb.setSpan(span, 2, 6, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
tv.setText(ssb);
tv.setTextSize(32);
Runnable action = new Runnable() {
@Override
public void run() {
span.update();
tv.invalidate();
tv.postDelayed(this, 50);
}
};
action.run();
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