如何在Android中利用TextView实现自定义竖排

public class MainActivity extends Activity implements OnTouchListener {    private VerticalTextView mVerticalTextView;    private TextView mTextView;    private int mTextCount;    @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     requestWindowFeature(Window.FEATURE_NO_TITLE);     setContentView(R.layout.activity_main);      mVerticalTextView = (VerticalTextView) findViewById(R.id.vertical_tv);     mTextView = (TextView) findViewById(R.id.content_tx);     mTextCount = mVerticalTextView.getText().length();     mVerticalTextView.setOnTouchListener(this);     mTextView.setBackgroundColor(Color.LTGRAY);   }    @Override   public boolean onTouch(View v, MotionEvent event) {     float verticalTextViewHeight = mVerticalTextView.getHeight();     float y = event.getY();     int sectionPosition = (int) Math.ceil((y / verticalTextViewHeight)         / (1f / mTextCount)) - 1;     if (sectionPosition < 0) {       sectionPosition = 0;     } else if (sectionPosition >= mTextCount) {       sectionPosition = mTextCount - 1;     }     String sectionLetter = String.valueOf(mVerticalTextView.getText()         .charAt(sectionPosition));     switch (event.getAction()) {     case MotionEvent.ACTION_DOWN:       mTextView.setVisibility(View.VISIBLE);       mTextView.setText(sectionLetter);       break;     case MotionEvent.ACTION_MOVE:       mTextView.setText(sectionLetter);       mTextView.setVisibility(View.VISIBLE);       break;      case MotionEvent.ACTION_UP:       mTextView.setVisibility(View.INVISIBLE);     default:       break;      }      return true;   } }