上述是自定义好的Textview，可以直接使用，具体如何实现，我们一起学习一下
1 public class FadeInTextView extends TextView { 2 3 4 private Rect textRect = new Rect(); 5 6 private StringBuffer stringBuffer = new StringBuffer(); 7 8 private String[] arr; 9 10 private int textCount; 11 12 private int currentIndex = -1; 13 14 /** 15 * 每个字出现的时间 16 */ 17 private int duration = 300; 18 private ValueAnimator textAnimation; 19 20 private TextAnimationListener textAnimationListener; 21 22 23 public FadeInTextView setTextAnimationListener(TextAnimationListener textAnimationListener) { 24 this.textAnimationListener = textAnimationListener; 25 return this; 26 } 27 28 public FadeInTextView(Context context) { 29 this(context, null); 30 } 31 32 public FadeInTextView(Context context, @Nullable AttributeSet attrs) { 33 super(context, attrs); 34 35 } 36 37 @Override 38 protected void onDraw(final Canvas canvas) { 39 super.onDraw(canvas); 40 if (stringBuffer != null) { 41 drawText(canvas, stringBuffer.toString()); 42 } 43 } 44 45 /** 46 * 绘制文字 47 * 48 * @param canvas 画布 49 */ 50 private void drawText(Canvas canvas, String textString) { 51 textRect.left = getPaddingLeft(); 52 textRect.top = getPaddingTop(); 53 textRect.right = getWidth() - getPaddingRight(); 54 textRect.bottom = getHeight() - getPaddingBottom(); 55 Paint.FontMetricsInt fontMetrics = getPaint().getFontMetricsInt(); 56 int baseline = (textRect.bottom + textRect.top - fontMetrics.bottom - fontMetrics.top) / 2; 57 //文字绘制到整个布局的中心位置 58 canvas.drawText(textString, getPaddingLeft(), baseline, getPaint()); 59 } 60 61 /** 62 * 文字逐个显示动画 通过插值的方式改变数据源 63 */ 64 private void initAnimation() { 65 66 //从0到textCount - 1 是设置从第一个字到最后一个字的变化因子 67 textAnimation = ValueAnimator.ofInt(0, textCount - 1); 68 //执行总时间就是每个字的时间乘以字数 69 textAnimation.setDuration(textCount * duration); 70 //匀速显示文字 71 textAnimation.setInterpolator(new LinearInterpolator()); 72 textAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { 73 @Override 74 public void onAnimationUpdate(ValueAnimator valueAnimator) { 75 int index = (int) valueAnimator.getAnimatedValue(); 76 //过滤去重，保证每个字只重绘一次 77 if (currentIndex != index) { 78 stringBuffer.append(arr[index]); 79 currentIndex = index; 80 //所有文字都显示完成之后进度回调结束动画 81 if (currentIndex == (textCount - 1)) { 82 if (textAnimationListener != null) { 83 textAnimationListener.animationFinish(); 84 } 85 } 86 87 invalidate(); 88 } 89 } 90 }); 91 } 92 93 /** 94 * 设置逐渐显示的字符串 95 * 96 * @param textString 97 * @return 98 */ 99 public FadeInTextView setTextString(String textString) { 100 if (textString != null) { 101 //总字数 102 textCount = textString.length(); 103 //存放单个字的数组 104 arr = new String[textCount]; 105 for (int i = 0; i < textCount; i++) { 106 arr[i] = textString.substring(i, i + 1); 107 } 108 initAnimation(); 109 } 110 111 return this; 112 } 113 114 /** 115 * 开启动画 116 * 117 * @return 118 */ 119 public FadeInTextView startFadeInAnimation() { 120 if (textAnimation != null) { 121 stringBuffer.setLength(0); 122 currentIndex = -1; 123 textAnimation.start(); 124 } 125 return this; 126 } 127 128 /** 129 * 停止动画 130 * 131 * @return 132 */ 133 public FadeInTextView stopFadeInAnimation() { 134 if (textAnimation != null) { 135 textAnimation.end(); 136 } 137 return this; 138 } 139 140 /** 141 * 回调接口 142 */ 143 public interface TextAnimationListener { 144 void animationFinish(); 145 } 146 } 147 148 Contact GitHub API Training Shop Blog About 149 150 © 2017 GitHub, Inc. Terms Privacy Security Status Help
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