自定义TextView带滚动字幕

虽然TextView有自带的滚动字幕，但在Listview中，仍需要让TextView能滚动字幕的话，对于焦点的取舍就麻烦了很多。而且若是有多个TextView需要滚动字幕的话，就不行了。正好看到一个帖子里网友提到自定义TextView让其滚动，真是一个非常不错的建议。也提供一下帖子的原地址:http://topic.youkuaiyun.com/u/20110728/09/0b52e21d-c609-4643-848b-0f42c28f6e0b.html

下面是我修改过的，把MyTextView作为ListView中的一部分去实现。

package com.abc;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Display;
import android.view.WindowManager;
import android.widget.TextView;

public class MyTextView extends TextView {
	public final static String TAG = MyTextView.class.getSimpleName();

	private float textLength = 0f;// 文本长度
	private float viewWidth = 0f;
	private float step = 0f;// 文字的横坐标
	private float y = 0f;// 文字的纵坐标
	private float x = 0f;//不滚动时的横坐标
	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
	private boolean first = true;

	public MyTextView(Context context) {
		super(context);
	}

	public MyTextView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public MyTextView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	/**
	 * 文本初始化，每次更改文本内容或者文本效果等之后都需要重新初始化一下
	 */
	public void init(WindowManager windowManager) {
		paint = getPaint();
		paint.setARGB(255, 0, 255, 0);
		text = getText().toString();
		textLength = paint.measureText(text);
		viewWidth = getWidth();
		if (viewWidth == 0) {
			if (windowManager != null) {
				Display display = windowManager.getDefaultDisplay();
				viewWidth = display.getWidth();
			}
		}
		if (textLength > viewWidth) {
			isStarting = true;
		}
		step = textLength;
		temp_view_plus_text_length = viewWidth + textLength;
		temp_view_plus_two_text_length = viewWidth + textLength * 2;
		y = getTextSize() + getPaddingTop();
		x = getPaddingLeft();
	}

	public Parcelable onSaveInstanceState() {
		Parcelable superState = super.onSaveInstanceState();
		SavedState ss = new SavedState(superState);

		ss.step = step;
		ss.isStarting = isStarting;

		return ss;

	}

	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);
		}

		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();
		}
	}

	/**
	 * 开始滚动
	 */
	public void startScroll() {
		isStarting = true;
		invalidate();
	}

	/**
	 * 停止滚动
	 */
	public void stopScroll() {
		isStarting = false;
		invalidate();
	}

	public void onDraw(Canvas canvas) {
		if (first) {
			viewWidth = getWidth();
			Log.i("width", "width="+viewWidth);
			first = false;
		}
		if (!isStarting) {
			canvas.drawText(text, x, y, paint);
			return;
		}
		canvas.drawText(text, temp_view_plus_text_length - step, y, paint);
		step += 0.5;
		if (step > temp_view_plus_two_text_length)
			step = textLength;
		invalidate();
	}

	public void setText(String text) {
		this.text = text;
		textLength = paint.measureText(text);
		if (textLength > viewWidth) {
			isStarting = true;
		} else {
			isStarting = false;
		}
		step = textLength;
		temp_view_plus_text_length = viewWidth + textLength;
		temp_view_plus_two_text_length = viewWidth + textLength * 2;
		y = getTextSize() + getPaddingTop();
		x = getPaddingLeft();
		invalidate();
	}
}

效果大体如下图：