實現原理：用兩個Textview來控制顯示，預設顯示短文字（限制行數）的Textview，當點選展開時，顯示全部文字的Textview。

public class MainActivity extends Activity {

	private TextView shortTxt, longTxt, txtOpenOrClose;
	private LinearLayout linearLayout;
	//是否初始化，防止無限制的判斷資訊是否過長
	private boolean isInit=false;
	private static final String OPEN = "展開";
	private static final String CLOSE = "收起";

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		initViews();
		String str = "《幻影車神3》是一部在2013年12月20日聖誕節上映的印度電影·由阿米爾·汗、卡特莉娜·卡芙、"
				+ "塔布萊特·貝賽爾等寶萊塢明星主演，Vijay Krishna Acharya執導。影片講述了一個原本在馬戲團混日子的男人，"
				+ "為了給父親報仇，決心去芝加哥一家腐敗銀行搞破壞，兩位孟買警察對他一路追蹤。";
//		 String str="這句話很短！";
		shortTxt.setText(str);
		longTxt.setText(str);
	}

	private void initViews() {
		// TODO Auto-generated method stub
		linearLayout = (LinearLayout) findViewById(R.id.id_linearLayout);
		shortTxt = (TextView) findViewById(R.id.id_textview);
		longTxt = (TextView) findViewById(R.id.id_textview2);
		txtOpenOrClose = (TextView) findViewById(R.id.id_openOrClose);
		
		txtOpenOrClose.setVisibility(View.GONE);
		txtOpenOrClose.setOnClickListener(clickListener);
		//添加回調方法，此方法在每次繪製檢視的時候回撥，如點選展開時就會呼叫此方法。
		ViewTreeObserver observer = linearLayout.getViewTreeObserver();
		observer.addOnPreDrawListener(onPreDrawListener);
	}

	
	/**
	 *按鈕單擊事件 
	 */
	private OnClickListener clickListener = new OnClickListener() {

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			//如果顯示的是 展開
			if (txtOpenOrClose.getText().equals(OPEN)) {
				//修改為 收起
				txtOpenOrClose.setText(CLOSE);
				//隱藏短文字的文字框
				shortTxt.setVisibility(View.GONE);
				//顯示長文字的文字框
				longTxt.setVisibility(View.VISIBLE);
			} else if (txtOpenOrClose.getText().equals(CLOSE)) {
				txtOpenOrClose.setText(OPEN);
				shortTxt.setVisibility(View.VISIBLE);
				longTxt.setVisibility(View.GONE);
			}
		}
	};

	/**
	 * 檢視繪製回撥方法
	 */
	private OnPreDrawListener onPreDrawListener = new OnPreDrawListener() {

		@Override
		public boolean onPreDraw() {
			// TODO Auto-generated method stub
			//如果已經初始化佈局，則不執行後面的方法
			if(isInit){
				return true;
			}
			//如果超過三行就顯示 “展開”  的按鈕
			if (isShowAll(shortTxt, longTxt)) {
				txtOpenOrClose.setVisibility(View.VISIBLE);
			}
			
			isInit=true;
			return true;
		}
	};

	/**
	 * 判斷文字是否超過三行，返回布林值
	 * @param shortTxt
	 * @param longTxt
	 * @return
	 */
	public boolean isShowAll(TextView shortTxt, TextView longTxt) {

		int shortHeight = shortTxt.getHeight();
		int longHeight = longTxt.getHeight();
		if (longHeight > shortHeight) {
			shortTxt.setVisibility(View.VISIBLE);
			longTxt.setVisibility(View.GONE);
			return true;
		} else {
			shortTxt.setVisibility(View.GONE);
			longTxt.setVisibility(View.VISIBLE);
			return false;
		}
		
	}
	
	
}
 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    android:orientation="vertical" >

    <LinearLayout
        android:id="@+id/id_linearLayout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/id_textview"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:maxLines="3"
            android:textSize="16sp"
            android:textColor="#000000" />

        <TextView
            android:id="@+id/id_textview2"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:textSize="16sp"
            android:textColor="#000000" />
    </LinearLayout>

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp" >

        <TextView
            android:id="@+id/id_openOrClose"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:text="展開"
            android:textColor="#0099FF" />
    </RelativeLayout>

</LinearLayout>