Android最实用TextView文字逐个打出效果

来源：互联网发布：ip广播软件编辑：程序博客网时间：2024/05/22 12:40

对于文字逐个打出效果，我们一下子想到的做法可能都是弄一个for循环，不断更改文本内容。

这法子表面看起来可以，但实际实用起来问题多多，比如对于多行居中对齐的文本，打出效果就不是渐进出来，因为受到对齐和换行的影响，随着文字增多，文本布局会不断变化。

下面看最实用和稳定的文字逐个打出效果自定义组件FadeInTextView。

1、FadeInTextView完全继承TextView的所有特性，没有任何负面影响，使用FadeInTextView就像使用TextView一样；

2、简单设置出效果：

（1）setFadeInDuration：设置打出效果总共时长；

（2）setMoveUnitLength：设置渐进步长为几个字符，默认为1；

（3）setFadeInMaskColor：设置遮罩颜色，即未显示文字区域的颜色。

完整源码如下：

import java.util.ArrayList;import java.util.List;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Paint.Style;import android.graphics.Rect;import android.text.Layout;import android.util.AttributeSet;import android.widget.TextView;public class FadeInTextView extends TextView {private static final int DEFAULT_UNIT_LENGTH = 2;private static final int DEFAULT_DURATION = 3820;private List<Rect> lineRects = new ArrayList<Rect>();private int duration = DEFAULT_DURATION;private int moveUnitLength;private int fromLine = 0;private int moveCount;private int fromStart;private int maskColor;private Paint paint;private FadeInListener fadeInListener;private volatile boolean fadeInFinished = false;private boolean hasCallListener = false;public FadeInTextView(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}public FadeInTextView(Context context, AttributeSet attrs) {super(context, attrs);}public FadeInTextView(Context context) {super(context);}public boolean isFadeInFinished() {return fadeInFinished;}public void setFadeInDuration(int duration) {this.duration = duration;}public int getFadeInDuration() {return duration;}public void setMoveUnitLength(int moveUnitLength) {this.moveUnitLength = moveUnitLength;}public void setFadeInMaskColor(int maskColor) {this.maskColor = maskColor;}public void setFadeInListener(FadeInListener fadeInListener) {this.fadeInListener = fadeInListener;}public void activateFadeInListener() {this.hasCallListener = false;}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);if (lineRects.isEmpty()) {getLineRects();if (fadeInListener != null && !hasCallListener) {fadeInListener.onFadeInStart(this);}}if (paint == null) {paint = new Paint();paint.setColor(maskColor);paint.setAntiAlias(true);paint.setStyle(Style.FILL);}for (int i = fromLine; i < lineRects.size(); i++) {Rect rect = new Rect(lineRects.get(i));if (i == fromLine) {rect.left = fromStart;}canvas.drawRect(rect, paint);}if (!computeNextFrame()) {fadeInFinished = true;if (fadeInListener != null && !hasCallListener) {fadeInListener.onFadeInEnd(this);hasCallListener = true;}return;}postDelayed(new Runnable() {@Overridepublic void run() {invalidate();}}, duration / moveCount);}private boolean computeNextFrame() {if (lineRects.size() <= fromLine) {return false;}Rect currentLineRect = lineRects.get(fromLine);if (fromStart >= currentLineRect.right) {return false;}fromStart = fromStart + moveUnitLength;if (fromStart >= currentLineRect.right) {fromLine++;if (lineRects.size() > fromLine) {fromStart = lineRects.get(fromLine).left;} else {fromStart = 0;}}return true;}private void getLineRects() {Layout layout = getLayout();if (layout == null) {return;}int lineCount = layout.getLineCount();int totalLength = 0;for (int i = 0; i < lineCount; i++) {Rect rect = new Rect();rect.left = (int) layout.getLineLeft(i);rect.right = (int) layout.getLineRight(i);rect.top = layout.getLineTop(i);rect.bottom = layout.getLineBottom(i);if (i == 0) {fromStart = rect.left;}lineRects.add(rect);totalLength = totalLength + rect.width();}if (moveUnitLength <= 0) {moveUnitLength = DEFAULT_UNIT_LENGTH;}moveCount = totalLength / moveUnitLength;if (moveCount <= 0) {moveCount = 1;}}public static interface FadeInListener {public void onFadeInStart(TextView tv);public void onFadeInEnd(TextView tv);}}

国际惯例

————————————————————————————————————————————————————————

作者：薄荷记账 （转载请注明原作者）

简洁稳定优雅无限可能！

1 0