像Google Plus评论一样的类似实施

Question

如果您使用过Google Plus Android应用，则会注意到不同评论之间不断轮换的评论Feed。

下面是它的截图：

有没有人知道如何实施类似的方法？我不是要求任何代码，而是想要了解如何实现它的基本思路。

请使用Google Plus Android应用并查看帖子评论的行为。你会明白我在问什么。

Answer 1

我怀疑这是一个与此类似的自定义View，请记得从xml手动调整宽度和高度：

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;

public class RotatingView extends View {

public static class RotatingData {
    String data;

    public RotatingData(String data) {
        super();
        this.data = data;
    }
}

public interface OnItemRotatedListener {
    public void onItemRotated(RotatingData data);
}

private List<RotatingData> mList;
private Paint mPaint;
private Handler mHandler;
private int mCurrentSelection;
private OnItemRotatedListener mItemRotatedListener;
private Random mRandom;

public RotatingView(Context context) {
    this(context, null);
}

public RotatingView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public RotatingView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mPaint = new Paint();
    mHandler = new Handler();
    mRandom = new Random();
    List<RotatingData> list = new ArrayList<RotatingView.RotatingData>();
    list.add(new RotatingData("0th item selected"));
    list.add(new RotatingData("1st item selected"));
    list.add(new RotatingData("2nd item selected"));
    setRotatingData(list);
    setSelection(0);
}

private void setSelection(int i) {
    mCurrentSelection = i;
    invokeListener(mList.get(i));
    invalidate();
}

public void setRotatingData(List<RotatingData> list) {
    mList = list;
    invalidate();
}

public OnItemRotatedListener getItemRotatedListener() {
    return mItemRotatedListener;
}

public void setItemRotatedListener(OnItemRotatedListener itemRotatedListener) {
    mItemRotatedListener = itemRotatedListener;
    invokeListener(mList.get(mCurrentSelection));
}

private void invokeListener(RotatingData data) {
    if (mItemRotatedListener != null) {
        mItemRotatedListener.onItemRotated(data);
    }
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    final List<RotatingData> list = mList;
    final int count = list.size();
    final float w = getMeasuredWidth() / (float) count;
    final int h = getMeasuredHeight();
    int left = 0;
    final Paint paint = mPaint;
    for (int i = 0; i < list.size(); i++) {
        if (i == mCurrentSelection) {
            paint.setColor(Color.DKGRAY);
        } else {
            paint.setColor(Color.LTGRAY);
        }
        canvas.drawRect(left, 0, left + w, h, paint);
        left += w;
    }
}

@Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    startRotating();
}

private void startRotating() {
    mHandler.postDelayed(new Runnable() {

        @Override
        public void run() {
            mCurrentSelection++;
            mCurrentSelection %= mList.size();
            setSelection(mCurrentSelection);
            mHandler.postDelayed(this, mRandom.nextInt(1000) + 1000);
        }
    }, mRandom.nextInt(1000) + 1000);
}

@Override
protected void onDetachedFromWindow() {
    super.onDetachedFromWindow();
    stopRotating();
}

private void stopRotating() {
    mHandler.removeCallbacksAndMessages(null);
}
}