跑马灯 TextView

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;


/**
* 跑马灯
*/
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 += 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();

}

}