/** * 簡易彈幕效果實現 * Created by admin on 15-6-4. */public class MainActivity extends ActionBarActivity {  private MyHandler handler;  //彈幕內容  private TanmuBean tanmuBean;  //放置彈幕內容的父組件  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[]{"測試一下", "彈幕這東西真不好做啊", "總是出現各種問題~~", "也不知道都是為什么？麻煩！", "哪位大神可以幫幫我??？", "I need your help.",        "測試一下", "彈幕這東西真不好做啊", "總是出現各種問題~~", "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.",        "測試一下", "彈幕這東西真不好做啊", "總是出現各種問題~~", "也不知道都是為什么？麻煩！", "哪位大神可以幫幫我??？", "I need your help."});    handler = new MyHandler(this);    //開始彈幕    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();    //計算本條彈幕的topMargin(隨機值，但是與屏幕中已有的不重復)    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);  }  //記錄當前仍在顯示狀態的彈幕的位置（避免重復）  private Set<Integer> existMarginValues = new HashSet<>();  private int linesCount;  private int getRandomTopMargin() {    //計算用于彈幕顯示的空間高度    if (validHeightSpace == 0) {      validHeightSpace = containerVG.getBottom() - containerVG.getTop()          - containerVG.getPaddingTop() - containerVG.getPaddingBottom();    }    //計算可用的行數    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 {  /**   * 創建平移動畫   */  public static Animation createTranslateAnim(Context context, int fromX, int toX) {    TranslateAnimation tlAnim = new TranslateAnimation(fromX, toX, 0, 0);    //自動計算時間    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  @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;  }}