android TextView 垂直自动滚动字幕实现
openkk
13年前
前段时间,在网上搜到一个帖子,textview 水平自动滚动字幕的实现,今日项目需要垂直滚动字幕。其实现原理和水品一样。都是重写textview的onDraw方法。
实现垂直自动滚动字幕需要2点需要注意
1.需要根据textview的宽度和字体的大小计算滚动字幕有多少行。实现这个功能,需要重新写两个方法:1.onMeasure,2.onDraw.因为需要获取textview的宽度,于是需要在onMeasure方法里面调用如下代码。具体方法如下:
public VerticalScrollTextView extends TextView { private float step =0f; private Paint mPaint; private String text; private float width; private List<String> textList = new ArrayList<String>(); //分行保存textview的显示信息。 public VerticalScrollTextView(Context context, AttributeSet attrs) { super(context, attrs); } public VerticalScrollTextView(Context context) { super(context); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); width = MeasureSpec.getSize(widthMeasureSpec); final int widthMode = MeasureSpec.getMode(widthMeasureSpec); if (widthMode != MeasureSpec.EXACTLY) { throw new IllegalStateException("ScrollLayout only canmCurScreen run at EXACTLY mode!"); } float length = 0; if(text==null|text.length()==0){ return ; } //下面的代码是根据宽度和字体大小,来计算textview显示的行数。 textList.clear(); StringBuilder builder = new StringBuilder(); for(int i=0;i<text.length();i++){ Log.e("textviewscroll",""+i+text.charAt(i)); if(length<width){ builder.append(text.charAt(i)); length += mPaint.measureText(text.substring(i, i+1)); if(i==text.length()-1){ Log.e("textviewscroll",""+i+text.charAt(i)); textList.add(builder.toString()); } }else{ textList.add(builder.toString().substring(0,builder.toString().length()-1)); builder.delete(0, builder.length()-1) ; length= mPaint.measureText(text.substring(i, i+1)); i--; } } } //下面代码是利用上面计算的显示行数,将文字画在画布上,实时更新。 @Override public void onDraw(Canvas canvas) { for (int i = 0; i < textList.size(); i++) { canvas.drawText(textList.get(i), 0, this.getHeight()+(i+1)*mPaint.getTextSize()-step, getPaint()); } invalidate(); step = step+0.3f; if (step >= this.getHeight()+textList.size()*mPaint.getTextSize()) { step = 0; } } }
还有一些扩展功能没有加,比方说滚动的速度设定,滚动多长时间就停止滚动。
转自:http://blog.csdn.net/fengyoujie/article/details/7296941