我正在开发 Android 应用程序，其主要目的是在底部显示 CNN 突发新闻样式栏和一些图片。我创建了两个自定义视图，一个用于显示照片，第二个用于显示栏。它在指定的时间内一次显示一张图片，并将当前图片与队列中的下一张交换。
为了使底部栏中的文本动画化，我使用了画布、onDraw() 和 handler.postDelayed。该解决方案的结果很差。文本移动不流畅，尤其是在交换图像时。
我应该用什么代替画布？是否有任何基于 OpenGL 的库可以使这项任务相对轻松？我尝试使用 AndEngine，但它缺乏文档和线程问题使我不再使用它。
public class Infobar extends View {
private List<Message> messages;
private Handler handler;
private Paint boxPaint;
private Paint defaultTextPaint;
private Paint importantTextPaint;
private long offset = 0;
private long maxOffset = 1000;
private int textWidth = 1000;
private int textHeight = 50;
private int measuredWidth;
private int measuredHeight;
private Runnable animateRunnable = new Runnable() {
public void run() {
animateMessage();
}
};
long startTime = new Date().getTime();
private int backgroundCol = Color.parseColor("#ffff00");
private int textColor = Color.parseColor("#000000");
private static final int FRAME_DELAY = 10;
private static final int FRAME_SHIFT = 3;
private static final int EMPTY_SPACE = 2;
private static final String SEPARATOR = " ✩ ";
private static final int TEXT_SIZE = 35;
public Infobar(Context context, AttributeSet attrs) {
super(context, attrs);
handler = new Handler();
messages = new ArrayList<Message>();
boxPaint = new Paint();
defaultTextPaint = new Paint();
defaultTextPaint.setColor(getResources().getColor(R.color.info_bar_default_text_color));
importantTextPaint = new Paint();
importantTextPaint.setColor(getResources().getColor(R.color.info_bar_important_text_color));
handler.postDelayed(animateRunnable, FRAME_DELAY);
}
public void setMessagesList(List<Message> list) {
messages = list;
}
public void setBackgroundColor(String color) {
backgroundCol = Color.parseColor(color);
}
public void setTextColor(String color) {
textColor = Color.parseColor(color);
}
public List<Message> getMessagesList() {
return messages;
}
private String getMessagesString() {
StringBuilder builder = new StringBuilder();
for(Message message : messages) {
builder.append(message.content);
if(messages.indexOf(message) != (messages.size() - 1)) {
builder.append(SEPARATOR);
}
}
return builder.toString();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
measuredWidth = getMeasuredWidth();
measuredHeight = getMeasuredHeight();
}
@Override
protected void onDraw(Canvas canvas) {
drawBackground(canvas, false);
drawMessage(canvas, getMessagesString());
super.onDraw(canvas);
}
private void drawBackground(Canvas canvas, boolean important) {
boxPaint.setColor(backgroundCol) ;
canvas.drawRect(0, 0, measuredWidth, measuredHeight, boxPaint);
}
private void drawMessage(Canvas canvas, String message) {
defaultTextPaint.setTextSize(TEXT_SIZE);
Rect bounds = new Rect();
defaultTextPaint.getTextBounds(message, 0, message.length(), bounds);
defaultTextPaint.setColor(textColor);
textWidth = bounds.width();
textHeight = bounds.height();
int positionX = measuredWidth - (int)offset;
int positionY = measuredHeight - textHeight/2;
if(offset > (measuredWidth + textWidth)) {
offset = 0;
positionX = measuredWidth;
}
canvas.drawText(message, positionX, positionY, defaultTextPaint);
}
private void animateMessage() {
offset += FRAME_SHIFT;
//offset = Math.round((new Date().getTime() - startTime) * 0.2) % (measuredWidth + textWidth);
invalidate();
handler.removeCallbacks(animateRunnable);
handler.postDelayed(animateRunnable, FRAME_DELAY);
}
}