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Android文字跑马灯控件（文本自动滚动控件）
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.view.Display;
import android.view.View;
import android.view.WindowManager;
import android.view.View.OnClickListener;
import android.widget.TextView;

/** *//**
*
* TODO 单行文本跑马灯控件
*
* @author tianlu
* @version 1.0
* Create At : 2010-2-16 下午09:35:03
*/
public class AutoScrollTextView extends TextView implements OnClickListener {
public final static String TAG = AutoScrollTextView.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 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);
initView();
}

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

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

/** *//**
* 初始化控件
*/
private void initView()
{
setOnClickListener(this);
}

/** *//**
* 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();
text = getText().toString();
textLength = paint.measureText(text);
viewWidth = getWidth();
if(viewWidth == 0)
{
if(windowManager != null)
{
Display display = windowManager.getDefaultDisplay();
viewWidth = display.getWidth();
}
}
step = textLength;
temp_view_plus_text_length = viewWidth + textLength;
temp_view_plus_two_text_length = viewWidth + textLength * 2;
y = getTextSize() + getPaddingTop();
}
@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];
}

@Override
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();
}


@Override
public void onDraw(Canvas canvas) {
canvas.drawText(text, temp_view_plus_text_length - step, y, paint);
if(!isStarting)
{
return;
}
step += 0.5;
if(step > temp_view_plus_two_text_length)
step = textLength;
invalidate();

}

@Override
public void onClick(View v) {
if(isStarting)
stopScroll();
else
startScroll();

}

}
实现了宽度的判断，文本自动滚动及开始和停止滚动等功能。

在UI xml中的配置如下：

<cn.tigertian.ui.AutoScrollTextView android:id="@+id/TextViewNotice"
android:layout_height="30px" android:layout_width="fill_parent"
android:text="@string/test_notice_1" android:textColor="#000" android:inputType="text"
android:background="#EEE" android:textSize="20px"></cn.tigertian.ui.AutoScrollTextView>

在Activity中的使用方法如下：
//启动公告滚动条
autoScrollTextView = (AutoScrollTextView)findViewById(R.id.TextViewNotice);
autoScrollTextView.init(getWindowManager());
autoScrollTextView.startScroll();

如果想改变跑马灯的文字内容或者文字效果，则在调用完setText方法之后，需要再调用一下init(WindowManager windowManager)方法，重新进行初始化和相关参数的计算。