/**
 * 簡(jiǎn)易彈幕效果實(shí)現(xiàn)
 * Created by admin on 15-6-4.
 */
public class MainActivity extends ActionBarActivity {
  private MyHandler handler;
  //彈幕內(nèi)容
  private TanmuBean tanmuBean;
  //放置彈幕內(nèi)容的父組件
  private RelativeLayout containerVG;
  //父組件的高度
  private int validHeightSpace;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    containerVG = (RelativeLayout) findViewById(R.id.tanmu_container);
    tanmuBean = new TanmuBean();
    tanmuBean.setItems(new String[]{"測(cè)試一下", "彈幕這東西真不好做啊", "總是出現(xiàn)各種問(wèn)題~~", "也不知道都是為什么？麻煩！", "哪位大神可以幫幫我啊？", "I need your help.",
        "測(cè)試一下", "彈幕這東西真不好做啊", "總是出現(xiàn)各種問(wèn)題~~", "也不知道都是為什么？麻煩！", "哪位大神可以幫幫我?。?, "I need your help.",
        "測(cè)試一下", "彈幕這東西真不好做啊", "總是出現(xiàn)各種問(wèn)題~~", "也不知道都是為什么？麻煩！", "哪位大神可以幫幫我啊？", "I need your help."});
    handler = new MyHandler(this);
    //開(kāi)始彈幕
    View startTanmuView = findViewById(R.id.startTanmu);
    startTanmuView.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        if (containerVG.getChildCount() > 0) {
          return;
        }
        existMarginValues.clear();
        new Thread(new CreateTanmuThread()).start();
      }
    });
  }
  //每2s自動(dòng)添加一條彈幕
  private class CreateTanmuThread implements Runnable {
    @Override
    public void run() {
      int N = tanmuBean.getItems().length;
      for (int i = 0; i < N; i++) {
        handler.obtainMessage(1, i, 0).sendToTarget();
        SystemClock.sleep(2000);
      }
    }
  }
  //需要在主線城中添加組件
  private static class MyHandler extends Handler {
    private WeakReference<MainActivity> ref;
    MyHandler(MainActivity ac) {
      ref = new WeakReference<>(ac);
    }
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      if (msg.what == 1) {
        MainActivity ac = ref.get();
        if (ac != null && ac.tanmuBean != null) {
          int index = msg.arg1;
          String content = ac.tanmuBean.getItems()[index];
          float textSize = (float) (ac.tanmuBean.getMinTextSize() * (1 + Math.random() * ac.tanmuBean.getRange()));
          int textColor = ac.tanmuBean.getColor();
          ac.showTanmu(content, textSize, textColor);
        }
      }
    }
  }
  private void showTanmu(String content, float textSize, int textColor) {
    final TextView textView = new TextView(this);
    textView.setTextSize(textSize);
    textView.setText(content);
//    textView.setSingleLine();
    textView.setTextColor(textColor);
    int leftMargin = containerVG.getRight() - containerVG.getLeft() - containerVG.getPaddingLeft();
    //計(jì)算本條彈幕的topMargin(隨機(jī)值，但是與屏幕中已有的不重復(fù))
    int verticalMargin = getRandomTopMargin();
    textView.setTag(verticalMargin);
    LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
    params.topMargin = verticalMargin;
    textView.setLayoutParams(params);
    Animation anim = AnimationHelper.createTranslateAnim(this, leftMargin, -ScreenUtils.getScreenW(this));
    anim.setAnimationListener(new Animation.AnimationListener() {
      @Override
      public void onAnimationStart(Animation animation) {
      }
      @Override
      public void onAnimationEnd(Animation animation) {
        //移除該組件
        containerVG.removeView(textView);
        //移除占位
        int verticalMargin = (int) textView.getTag();
        existMarginValues.remove(verticalMargin);
      }
      @Override
      public void onAnimationRepeat(Animation animation) {
      }
    });
    textView.startAnimation(anim);
    containerVG.addView(textView);
  }
  //記錄當(dāng)前仍在顯示狀態(tài)的彈幕的位置（避免重復(fù)）
  private Set<Integer> existMarginValues = new HashSet<>();
  private int linesCount;
  private int getRandomTopMargin() {
    //計(jì)算用于彈幕顯示的空間高度
    if (validHeightSpace == 0) {
      validHeightSpace = containerVG.getBottom() - containerVG.getTop()
          - containerVG.getPaddingTop() - containerVG.getPaddingBottom();
    }
    //計(jì)算可用的行數(shù)
    if (linesCount == 0) {
      linesCount = validHeightSpace / ScreenUtils.dp2px(this, tanmuBean.getMinTextSize() * (1 + tanmuBean.getRange()));
      if (linesCount == 0) {
        throw new RuntimeException("Not enough space to show text.");
      }
    }
    //檢查重疊
    while (true) {
      int randomIndex = (int) (Math.random() * linesCount);
      int marginValue = randomIndex * (validHeightSpace / linesCount);
      if (!existMarginValues.contains(marginValue)) {
        existMarginValues.add(marginValue);
        return marginValue;
      }
    }
  }
}

public class AnimationHelper {
  /**
   * 創(chuàng)建平移動(dòng)畫(huà)
   */
  public static Animation createTranslateAnim(Context context, int fromX, int toX) {
    TranslateAnimation tlAnim = new TranslateAnimation(fromX, toX, 0, 0);
    //自動(dòng)計(jì)算時(shí)間
    long duration = (long) (Math.abs(toX - fromX) * 1.0f / ScreenUtils.getScreenW(context) * 4000);
    tlAnim.setDuration(duration);
    tlAnim.setInterpolator(new DecelerateAccelerateInterpolator());
    tlAnim.setFillAfter(true);
    return tlAnim;
  }
}

public class DecelerateAccelerateInterpolator implements Interpolator {
  //input從0～1，返回值也從0～1.返回值的曲線表征速度加減趨勢(shì)
  @Override
  public float getInterpolation(float input) {
    return (float) (Math.tan((input * 2 - 1) / 4 * Math.PI)) / 2.0f + 0.5f;
  }
}

public class TanmuBean {
  private String[] items;
  private int color;
  private int minTextSize;
  private float range;
  public TanmuBean() {
    //init default value
    color = Color.parseColor("#eeeeee");
    minTextSize = 16;
    range = 0.5f;
  }
  public String[] getItems() {
    return items;
  }
  public void setItems(String[] items) {
    this.items = items;
  }
  public int getColor() {
    return color;
  }
  public void setColor(int color) {
    this.color = color;
  }
  /**
   * min textSize, in dp.
   */
  public int getMinTextSize() {
    return minTextSize;
  }
  public void setMinTextSize(int minTextSize) {
    this.minTextSize = minTextSize;
  }
  public float getRange() {
    return range;
  }
  public void setRange(float range) {
    this.range = range;
  }
}