android 帶箭頭的textview文字伸縮效果

雖然是自己做的 還是不太懂 都是看網上的方法自己總結的 如果大家有質量好的demo 請分享一下

主要就是一個方法 幾個變量限制 xml文件就不貼了 普通的TextView

public class TextViewActivity extends Activity {

	private TextView tv;

	private String status = "up";
	private String str = "Android是一種基於Linux的自由及開放源代碼的操作系統，主要使用於移動設備，如智能手機和平板電腦，由Google公司和開放手機聯盟領導及開發。";
	private String str_show = "";
	private int maxlength = 50;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		tv = (TextView) findViewById(R.id.textView1);
		if (str.length() < maxlength) {
			tv.setText(str);
		} else {
			changStatus();
		}
	}

	private void changStatus() {
		tv.setText("");
		Drawable drawable = null;
		if (status.equals("down")) {
			drawable = getResources().getDrawable(R.drawable.icon_arrow_up);
			status = "up";
			str_show = str;
			tv.setMaxLines(10000);
		} else if (status.equals("up")) {
			drawable = getResources().getDrawable(R.drawable.icon_arrow_down);
			status = "down";
			tv.setMaxLines(2);
			str_show = str.substring(0, maxlength);
			str_show += "...";
		}
		String spanString = str_show;
		spanString = spanString.substring(0, spanString.length());
		drawable.setBounds(0, 0, drawable.getIntrinsicWidth(),
				drawable.getIntrinsicHeight());
		SpannableString spannable = new SpannableString(spanString.toString()
				+ "s");
		ImageSpan span = new ImageSpan(drawable, ImageSpan.ALIGN_BASELINE);
		spannable.setSpan(span, spanString.toString().length(), spanString
				.toString().length() + "s".length(),
				Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
		ClickableSpan rightClickableSpan = new ClickableSpan() {

			@Override
			public void onClick(View view) {
				changStatus();
			}
		};
		spannable.setSpan(rightClickableSpan, spanString.toString().length(),
				spanString.toString().length() + "s".length(),
				Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
		tv.setText(spannable);
		tv.setMovementMethod(new MyTouch());

	}

}