Android 实现跑马灯效果

Android中实现跑马灯效果有多种方式,本篇简单介绍下:

1: TextView属性实现

这里需要注意下:

1. 需要限制textview的宽度,不能设置为wrap_content
2. 启动跑马灯效果需要获取焦点requestFocus().

2: 代码实现

tv2.setSingleLine();
tv2.setHorizontallyScrolling(true);
tv2.setEllipsize(TextUtils.TruncateAt.MARQUEE);
tv2.setMarqueeRepeatLimit(-1);
tv2.setFocusable(true);
tv2.setFocusableInTouchMode(true);
tv2.requestFocus();

3: 自定义 view实现

这里可以使用动画的效果实现.

package com.test.marquee;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.LinearInterpolator;
import androidx.annotation.Nullable;
public class MarqueeView extends View {
    private String text;
    private Paint paint;
    private float textWidth;
    private float textX;
    private float viewWidth;
    private ValueAnimator animator;
    public MarqueeView(Context context) {
        super(context);
        init();
    }
    public MarqueeView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    public MarqueeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
    private void init() {
        text = "This is a marquee";
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setTextSize(50);
        paint.setColor(Color.BLACK);
        textWidth = paint.measureText(text);
    }
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        viewWidth = w;
        textX = viewWidth;
    }
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawText(text, textX, getHeight() / 2, paint);
    }
    public void startMarquee() {
        animator= ValueAnimator.ofFloat(viewWidth, -textWidth);
        animator.setDuration(5000);
        animator.setInterpolator(new LinearInterpolator());
        animator.setRepeatCount(ValueAnimator.INFINITE);
        animator.addUpdateListener(animation -> {
            textX = (float) animation.getAnimatedValue();
            invalidate();
        });
        animator.start();
    }
    public void stopMarquee() {
        // 停止动画
        if (animator!=null) animator.cancel();
    }
}

4: 实现竖直效果的跑马灯

package com.test.marquee;
import android.content.Context;
import android.graphics.Canvas;
import android.text.TextUtils;
import android.text.method.ScrollingMovementMethod;
import android.util.AttributeSet;
import androidx.annotation.Nullable;
import androidx.appcompat.widget.AppCompatTextView;
public class VerticalMarqueeTextView extends AppCompatTextView {
    private float offsetY;
    public VerticalMarqueeTextView(Context context) {
        super(context);
        init();
    }
    public VerticalMarqueeTextView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    private void init() {
        setSingleLine();
        setEllipsize(TextUtils.TruncateAt.MARQUEE);
        setMarqueeRepeatLimit(-1);
        setFocusable(true);
        setFocusableInTouchMode(true);
        setHorizontallyScrolling(true);
        setMovementMethod(ScrollingMovementMethod.getInstance());
    }
    @Override
    protected void onDraw(Canvas canvas) {
        canvas.translate(0, offsetY);
        super.onDraw(canvas);
    }
    @Override
    public boolean isFocused() {
        return true;
    }
    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        post(new Runnable() {
            @Override
            public void run() {
                offsetY -= 1;
                if (offsetY <= -getHeight()) {
                    offsetY = 0;
                }
                invalidate();
                postDelayed(this, 20);
            }
        });
    }
}