Android实现可以展开的TextView

public class ExpandableTextView extends TextView { 
 private static int MIN_LINE_NUM = 2; 
 private static int MAX_LINE_NUM = 20; 
 private int lineNum = MIN_LINE_NUM; 
 private boolean mIsExpanded = false; 
 Bitmap bitmapDown; 
 Bitmap bitmapUp; 
 int w, h; 
 /** 点击事件listener */ 
 private OnClickListener mOnClickListener; 
 
 public ExpandableTextView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  init(context, attrs); 
 } 
 
 private void init(Context context, AttributeSet attrs) { 
  setMaxLines(lineNum); 
  bitmapDown = BitmapFactory.decodeResource(getResources(), R.drawable.update_detail_down); 
  bitmapUp = BitmapFactory.decodeResource(getResources(), R.drawable.update_detail_up); 
  w = bitmapDown.getWidth() + (int) context.getResources().getDimension(R.dimen.expand_textview_right); 
  h = bitmapDown.getHeight() + (int) context.getResources().getDimension(R.dimen.expand_textview_bottom); 
   
  super.setOnClickListener(new OnClickListener() { 
   @Override 
   public void onClick(View v) { 
    if (lineNum == MIN_LINE_NUM) { 
     lineNum = MAX_LINE_NUM; 
     setMaxLines(lineNum); 
    } else { 
     lineNum = MIN_LINE_NUM; 
     setMaxLines(lineNum); 
    } 
    if (mOnClickListener != null) { 
     mOnClickListener.onClick(v); 
    } 
   } 
  }); 
 } 
 
 @Override 
 public void setOnClickListener(OnClickListener listener) { 
  if (!isClickable()) { 
   setClickable(true); 
  } 
  mOnClickListener = listener; 
 } 
 
 @Override 
 public void setMaxLines(int maxlines) { 
  super.setMaxLines(maxlines); 
 
  if (lineNum == MAX_LINE_NUM) { 
   mIsExpanded = true; 
  } else { 
   mIsExpanded = false; 
  } 
 } 
 
 public boolean isExpanded() { 
  return mIsExpanded; 
 } 
 
 @Override 
 protected void onDraw(Canvas canvas) { 
  if (getLineCount() <= MIN_LINE_NUM) { 
   super.onDraw(canvas); 
   return; 
  } 
  if (lineNum == MIN_LINE_NUM) { 
   canvas.drawBitmap(bitmapDown, getWidth() - w, getHeight() - h, null); 
  } else { 
   canvas.drawBitmap(bitmapUp, getWidth() - w, getHeight() - h, null); 
  } 
  super.onDraw(canvas); 
 } 
 
 
 public void setMaxLine(int line) { 
  lineNum = line; 
  setMaxLines(line); 
 } 
} 

<RelativeLayout 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" 
 android:background="#FFFFFF" > 
 
 <TextView 
  android:id="@+id/detail_action" 
  android:textColor="#000000" 
  android:textSize="11sp" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:layout_alignParentTop="true" 
  android:layout_marginRight="8dip" 
  android:drawablePadding="4dip" 
  android:paddingBottom="10dip" 
  android:paddingTop="10dip" 
  android:singleLine="true" 
  android:text="sdfkljsfiosjdfiosfjsiofjsdifsd" /> 
 
 <com.example.view.ExpandableTextView 
  android:id="@+id/textview" 
  android:layout_width="100dp" 
  android:layout_height="wrap_content" 
  android:layout_below="@id/detail_action" 
  android:lineSpacingExtra="4dip" 
  android:paddingBottom="-40dip" 
  android:paddingRight="48dip" 
  android:text="adfsfsfewrwerwerwerqRWgdffdfdfERSAFSDFSDFSDd" 
  android:layout_marginTop="-5dip" 
  android:textColor="#000000" > 
 </com.example.view.ExpandableTextView> 
  
  
  <TextView 
  android:id="@+id/detail_action1" 
  android:textColor="#000000" 
  android:textSize="11sp" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:layout_below="@id/textview" 
  android:layout_marginRight="8dip" 
  android:drawablePadding="4dip" 
  android:paddingBottom="10dip" 
  android:paddingTop="10dip" 
  android:singleLine="true" 
  android:text="sdfkljsfiosjdfiosfjsiofjsdifsd" /> 
 
</RelativeLayout>