有时候在xml中写的跑马灯效果不滚动：原因有以下

总结一下跑马灯的实现效果，网上比较流行的有两种，测试过了都可以实现文字滚动效果，建议使用第一种，因为可以更好地控制文字滚动速度、样式、字体等属性，第二种方法，还没有找到控制的方法！

第一种：

控件类：AutoScrollTextView 继承了TextView并做了一些修改，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。

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;

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();
    }
   
   
    private void initView()
    {
        setOnClickListener(this);
    }
   
   
    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();
        }
    }

public void startScroll()
    {
        isStarting = true;
        invalidate();
    }
   
   
    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;//0.5为文字滚动速度。
        if(step > temp_view_plus_two_text_length)
            step = textLength;
        invalidate();

}

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

}

xml中使用方法：

<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>

Activity中使用方法：

//启动公告滚动条
        autoScrollTextView = (AutoScrollTextView)findViewById(R.id.TextViewNotice);
        autoScrollTextView.init(getWindowManager());
        autoScrollTextView.startScroll();

注：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方法，重新进行初始化和相关参数的计算。

第二种：