允許使用者變更標題軌道

此程式是如何建立按鈕的範例，讓使用者選取隱藏字幕軌道。

  1. 建立按鈕以變更隱藏字幕軌道。

    <Button
  android:id="@+id/selectCC"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_alignParentBottom="true"
  android:layout_alignParentRight="true"
  android:layout_marginRight="10dp"
  android:onClick="selectClosedCaptioningClick"
  android:text="CC" />

  2. 將可用隱藏字幕音軌清單轉換為字串陣列。

    相應地標籤具有活動（即TVSDK已發現資料的頻道）的隱藏字幕軌道。

    /**
* Converts the closed captions tracks to a string array.
*
* @return array of CC tracks
*/
private String[] getCCsAsArray() {
    List<String> closedCaptionsTracksAsStrings = new ArrayList<String>();
    MediaPlayerItem currentItem = mediaPlayer.getCurrentItem();
    if (currentItem != null) {
        List<ClosedCaptionsTrack> closedCaptionsTracks =
        currentItem.getClosedCaptionsTracks();
        Iterator<ClosedCaptionsTrack> iterator = closedCaptionsTracks.iterator();
        while (iterator.hasNext()) {
            ClosedCaptionsTrack closedCaptionsTrack = iterator.next();
            String isActive = closedCaptionsTrack.isActive() ? " (" +
              getString(R.string.active)+ ")" : "";
            closedCaptionsTracksAsStrings.add(closedCaptionsTrack.getName() +
              isActive);
        }
    }
    return closedCaptionsTracksAsStrings.
      toArray(new String[closedCaptionsTracksAsStrings.size()]);
}

  3. 當使用者按一下按鈕時，會顯示對話方塊，列出所有預設的隱藏字幕軌道。

    public void selectClosedCaptioningClick(View view) {
    Log.i(LOG_TAG + "#selectClosedCaptions", "Displaying closed captions chooser dialog.");
    final String items[] = getCCsAsArray();
    final AlertDialog.Builder ab = new AlertDialog.Builder(this);
    ab.setTitle(R.string.PlayerControlCCDialogTitle);
    ab.setSingleChoiceItems(items, selectedClosedCaptionsIndex, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
            // Select the new closed captioning track.
            MediaPlayerItem currentItem = mediaPlayer.getCurrentItem();
            ClosedCaptionsTrack desiredClosedCaptionsTrack =
              currentItem.getClosedCaptionsTracks().get(whichButton);
            boolean result = currentItem.selectClosedCaptionsTrack(desiredClosedCaptionsTrack);
            if (result) {
                selectedClosedCaptionsIndex = whichButton;
            }
            // Dismiss dialog.
            dialog.cancel();
     }
    }).setNegativeButton(R.string.PlayerControlCCDialogCancel, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
            // Just cancel the dialog.
        }
    });
    ab.show();
}

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