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。