自定义具有跑马灯效果的两种方法

普通的TextView可以实现跑马灯，但是只有当焦点在它上面时才有效。如何做一个自动的跑马灯呢？第一种：继承TextView，然后重写isFocused()方法就可以了，简单！Java代码

import android.content.Context;  
import android.util.AttributeSet;  
import android.widget.TextView;  
  
public class ScrollForeverTextView extends TextView {  
  
    public ScrollForeverTextView(Context context) {  
        super(context);  
        // TODO Auto-generated constructor stub  
    }  
  
    public ScrollForeverTextView(Context context, AttributeSet attrs) {  
        super(context, attrs);  
    }  
  
    public ScrollForeverTextView(Context context, AttributeSet attrs,  
            int defStyle) {  
        super(context, attrs, defStyle);  
    }  
  
    @Override  
    public boolean isFocused() {  
        return true;  
    }  
  
}

使用时同TextView一样：Xml代码 

   <com.ql.view.ScrollForeverTextView 
   android:layout_width="fill_parent" 
   android:layout_height="wrap_content" 
   android:textSize="30px" 
   android:singleLine="true" 
   android:ellipsize="marquee" 
   android:marqueeRepeatLimit="marquee_forever" 
   android:textColor="@color/red" 
   android:text="1234567890wwwwwwwwwwwwwwwwwwwwww1234567890" 
   android:focusable="true" />

第2种：还是继承TextView，重写onDraw()，在onDraw中不停的重绘。
Java代码  

    
    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 CharSequence text = "";// 文本内容  
        private float speed = 0.5f;  
        private int textColor=0xFF000000;  
          
        public int getTextColor() {  
            return textColor;  
        }  
      
        public void setTextColor(int color) {  
            this.textColor = color;  
        }  
      
        public float getSpeed() {  
            return speed;  
        }  
      
        public void setSpeed(float speed) {  
            this.speed = speed;  
        }  
      
        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(float width) {  
            text=super.getText();  
            paint = super.getPaint();  
    //      Paint paint=new Paint();  
            text = getText().toString();  
            textLength = paint.measureText(text.toString());  
    //      viewWidth = getWidth();  
    //      if (viewWidth == 0) {  
    //          if (windowManager != null) {  
    //              Display display = windowManager.getDefaultDisplay();  
    //              viewWidth = display.getWidth();  
    //          }  
    //      }  
            viewWidth=width;  
            step = textLength;  
            temp_view_plus_text_length = viewWidth + textLength;  
            temp_view_plus_two_text_length = viewWidth + textLength * 2;  
            y = getTextSize() + getPaddingTop();  
            paint.setColor(textColor);  
        }  
      
        @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) {  
    //      super.onDraw(canvas);  
              
            canvas.drawText(text,0,text.length(), temp_view_plus_text_length - step, y, paint);  
            if (!isStarting) {  
                return;  
            }  
            step += speed;  
            if (step > temp_view_plus_two_text_length)  
                step = textLength;  
            invalidate();  
      
        }  
      
        @Override  
        public void onClick(View v) {  
            if (isStarting)  
                stopScroll();  
            else  
                startScroll();  
      
        }  
      
    }  

使用：Java代码  

marquee = (AutoScrollTextView) findViewById(R.id.marquee);  
//      marquee.setText(String.format(getResources().getString(R.string.marquee0),Consts.termno,"2010-12-28"));  
        marquee.setText("上证指数3000.15 6.81(0.37%)深圳成指3000.15 6.81(0.37%)");  
//      marquee.setTextColor(0xffff0000);//注意：颜色必须在这里设置，xml中设置无效！默认黑色。  
        //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(width)方法，重新进行初始化和相关参数的计算。  
        marquee.setSpeed(1.5f);  
        marquee.init(width);//width通常就是屏幕宽！  
        marquee.startScroll();

这2种跑马灯稍微有点区别，需要掂量着使用。
第1种跑马灯不能设置速度，并且要超过一行才会滚动。
第2种跑马灯只能设置单一颜色，且需要在代码中设置，不能同时设置多种颜色。速度设的不要过大(<=2.0f)，否则停顿现象比较明显。