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; 
  } 
} 

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)); 

public class VerticalTextView extends TextView { 
 
  /** 
   * 绘制整个VerticalTextView区域大小的画笔 
   */ 
  private Paint mPaint; 
  /** 
   * 绘制每个竖排字符间的间隔横线的画笔 
   */ 
  private Paint linePaint; 
  /** 
   * 绘制单个字符的画笔 
   */ 
  private Paint charPaint; 
 
  private char[] indexs; 
 
  private int textCount; 
 
  private String textString; 
 
  public VerticalTextView(Context context, AttributeSet attrs) { 
    this(context, attrs, 0); 
  } 
 
  public VerticalTextView(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
 
    mPaint = new Paint(); 
 
    linePaint = new Paint(); 
 
    charPaint = new Paint(); 
 
    textString = getText().toString(); 
    indexs = getKeyChar(textString); 
    textCount = textString.toCharArray().length; 
  } 
 
  @Override 
  protected void onDraw(Canvas canvas) { 
    float childHeight = getHeight() / textCount; 
    if (TextUtils.isEmpty(textString)) 
      return; 
    canvas.drawRect(0, 0, getWidth(), getHeight(), mPaint); 
    canvas.drawColor(Color.GRAY); 
 
    linePaint.setColor(Color.BLACK); 
 
    charPaint.setTextSize((float) (getWidth() * 0.75)); 
    charPaint.setTextAlign(Paint.Align.CENTER); 
 
    FontMetrics fm = charPaint.getFontMetrics(); 
    for (int i = 0; i < textCount; i++) { 
      canvas.drawLine(0, i * childHeight, getWidth(), i * childHeight, 
          linePaint); 
      canvas.drawText( 
          String.valueOf(indexs[i]), 
          getWidth() / 2, 
          (float) (((i + 0.5) * childHeight) - (fm.ascent + fm.descent) / 2), 
          charPaint); 
    } 
  } 
 
  protected char[] getKeyChar(String str) { 
    char[] keys = new char[str.length()]; 
    for (int i = 0; i < keys.length; i++) { 
      keys[i] = str.charAt(i); 
    } 
    return keys; 
  } 
} 

canvas.drawText(String.valueOf(indexs[i]),getWidth() / 2,(float) (((i + 0.5) * childHeight) -  
 
(fm.ascent + fm.descent) / 2 
 
),charPaint); 

(i + 0.5) * childHeight 

(fm.ascent + fm.descent) / 2 

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" > 
<com.example.demoindextextview.widget.VerticalTextView 
    android:id="@+id/vertical_tv" 
    android:layout_width="20dp" 
    android:layout_height="match_parent" 
    android:layout_gravity="right" 
    android:text="ABCDEFGsdfsf你好吗sdfsdklmnopqrstuvwxyz" /> 
 
<TextView  
  android:id="@+id/content_tx" 
  android:layout_gravity="center" 
  android:gravity="center" 
  android:layout_height="50dp" 
  android:layout_width="50dp" 
  android:textSize="30sp" 
  android:visibility="invisible"/> 
   
</FrameLayout>