Android基于TextView实现的跑马灯效果实例

package sweet.venst.act;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.View;
import android.view.WindowManager;
import android.view.View.MeasureSpec;
import android.view.View.OnClickListener;
import android.widget.TextView;
public class AutoScrollTextView extends TextView {
 public final static String TAG = AutoScrollTextView.class.getSimpleName();
 private float textLength = 0f;// 文本长度
 private int viewWidth = 0;
 private int viewHight = 300;
 private float step = 0f;// 文字的横坐标
 private float y = 0f;// 文字的纵坐标
 private float temp_view_plus_text_length = 0.0f;// 用于计算的临时变量
 private float temp_view_plus_two_text_length = 0.0f;// 用于计算的临时变量
 public boolean isStarting = false;// 是否开始滚动
 private Paint paint = null;// 绘图样式
 private String text = "";// 文本内容
 public AutoScrollTextView(Context context)
 {
 super(context);
 }
 public AutoScrollTextView(Context context, AttributeSet attrs)
 {
 super(context, attrs);
 }
 public AutoScrollTextView(Context context, AttributeSet attrs, int defStyle)
 {
 super(context, attrs, defStyle);
 }
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
 {
 // TODO Auto-generated method stub
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 int measureWidth = measureWidth(widthMeasureSpec);
 int measureHight = measureHeight(heightMeasureSpec);
 // int measureWidth = 1024;
 // int measureHight = 300;
 viewWidth = measureWidth;
 viewHight = measureHight;
 setMeasuredDimension(viewWidth, viewHight);
 }
 private int measureWidth(int widthMeasureSpec)
 {
 int specMode = MeasureSpec.getMode(widthMeasureSpec);
 int specSize = MeasureSpec.getSize(widthMeasureSpec);
 if (specMode == MeasureSpec.UNSPECIFIED) {
  return viewWidth;
 }
 else  {
   return viewWidth;
  }
 }
 private int measureHeight(int widthMeasureSpec) {
 int specMode = MeasureSpec.getMode(widthMeasureSpec);
 int specSize = MeasureSpec.getSize(widthMeasureSpec);
 if (specMode == MeasureSpec.UNSPECIFIED) {
  return viewHight;
 } else {
  return viewHight;
 }
 }
 public void setScrollText(String text)
 {
 this.text = text;
 inittextLength(text);
 // invalidate();
 }
 public void init(Context cx) {
 paint = getPaint();
 paint.setTextSize(40);
 paint.setColor(Color.WHITE);
 text = getText().toString();
 textLength = paint.measureText(text);
 viewWidth = getWidth();
 if (viewWidth == 0) {
  DisplayMetrics dm = new DisplayMetrics();
  dm = cx.getApplicationContext().getResources().getDisplayMetrics();
  viewWidth = dm.widthPixels;
 }
 step = textLength;
 temp_view_plus_text_length = viewWidth + textLength;
 temp_view_plus_two_text_length = viewWidth + textLength * 2;
 y = getTextSize() + getPaddingTop();
 }
 private void inittextLength(String text) {
 textLength = paint.measureText(text);
 step = textLength;
 temp_view_plus_text_length = viewWidth + textLength;
 temp_view_plus_two_text_length = viewWidth + textLength * 2;
 }
 @Override
 public Parcelable onSaveInstanceState() {
 Parcelable superState = super.onSaveInstanceState();
 SavedState ss = new SavedState(superState);
 ss.step = step;
 ss.isStarting = isStarting;
 return ss;
 }
 @Override
 public void onRestoreInstanceState(Parcelable state) {
 if (!(state instanceof SavedState)) {
  super.onRestoreInstanceState(state);
  return;
 }
 SavedState ss = (SavedState) state;
 super.onRestoreInstanceState(ss.getSuperState());
 step = ss.step;
 isStarting = ss.isStarting;
 }
 public static class SavedState extends BaseSavedState {
 public boolean isStarting = false;
 public float step = 0.0f;
 SavedState(Parcelable superState) {
  super(superState);
 }
 @Override
 public void writeToParcel(Parcel out, int flags) {
  super.writeToParcel(out, flags);
  out.writeBooleanArray(new boolean[] { isStarting });
  out.writeFloat(step);
 }
 public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
  public SavedState[] newArray(int size) {
  return new SavedState[size];
  }
  public SavedState createFromParcel(Parcel in) {
  return new SavedState(in);
  }
 };
 private SavedState(Parcel in) {
  super(in);
  boolean[] b = null;
  in.readBooleanArray(b);
  if (b != null && b.length > 0)
  isStarting = b[0];
  step = in.readFloat();
 }
 }
 public void startScroll() {
 isStarting = true;
 // invalidate();
 }
 public void stopScroll() {
 isStarting = false;
 // invalidate();
 }
 public void onDraw(Canvas canvas) {
 canvas.save();
 canvas.drawText(text, temp_view_plus_text_length - step, y, paint);
 if (!isStarting) {
  return;
 }
 step += 3.2;// 0.5为文字滚动速度。
 if (step > temp_view_plus_two_text_length)
  step = textLength;
 canvas.restore();
// invalidate();
 postInvalidate();
 }
}