Android TextView仿微信可折叠效果

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.LinearLayout;
import android.widget.TextView;
/**
* 可折叠的textview
*/
public class ExpandTextView extends LinearLayout {
public static final int DEFAULT_MAX_LINES = 3;
private TextView contentText;
private TextView textPlus;
private int showLines;
private ExpandStatusListener expandStatusListener;
private boolean isExpand;
public ExpandTextView(Context context) {
super(context);
initView();
}
public ExpandTextView(Context context, AttributeSet attrs) {
super(context, attrs);
initAttrs(attrs);
initView();
}
public ExpandTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initAttrs(attrs);
initView();
}
private void initAttrs(AttributeSet attrs) {
TypedArray typedArray = getContext().getTheme().obtainStyledAttributes(attrs, R.styleable.ExpandTextView, 0, 0);
try {
showLines = typedArray.getInt(R.styleable.ExpandTextView_showLines, DEFAULT_MAX_LINES);
}finally {
typedArray.recycle();
}
}
private void initView() {
setOrientation(LinearLayout.VERTICAL);
LayoutInflater.from(getContext()).inflate(R.layout.layout_magic_text, this);
contentText = (TextView) findViewById(R.id.contentText);
if(showLines   0){
contentText.setMaxLines(showLines);
}
textPlus = (TextView) findViewById(R.id.textPlus);
textPlus.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
String textStr = textPlus.getText().toString().trim();
if("全文".equals(textStr)){
contentText.setMaxLines(Integer.MAX_VALUE);
textPlus.setText("收起");
setExpand(true);
}else{
contentText.setMaxLines(showLines);
textPlus.setText("全文");
setExpand(false);
}
//通知外部状态已变更
if(expandStatusListener != null){
expandStatusListener.statusChange(isExpand());
}
}
});
}
public void setText(final CharSequence content){
//在开始绘制contentText内容时，进行监听
contentText.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
// 避免重复监听
contentText.getViewTreeObserver().removeOnPreDrawListener(this);
//获取当前文本的行数
int linCount = contentText.getLineCount();
if(linCount   showLines){
if(isExpand){
contentText.setMaxLines(Integer.MAX_VALUE);
textPlus.setText("收起");
}else{
contentText.setMaxLines(showLines);
textPlus.setText("全文");
}
textPlus.setVisibility(View.VISIBLE);
}else{
textPlus.setVisibility(View.GONE);
}
return true;
}
});
contentText.setText(content);
}
public void setExpand(boolean isExpand){
this.isExpand = isExpand;
}
public boolean isExpand(){
return this.isExpand;
}
public void setExpandStatusListener(ExpandStatusListener listener){
this.expandStatusListener = listener;
}
public interface ExpandStatusListener{
void statusChange(boolean isExpand);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
return textPlus.dispatchTouchEvent(event);
}
}

<?xml version="1.0" encoding="utf-8"? 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" 
<TextView
android:id="@+id/contentText"
android:textSize="18sp"
android:textColor="#000000"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text=""/ 
<TextView
android:id="@+id/textPlus"
android:textSize="18sp"
android:textColor="#666666"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:text=""/ 
</LinearLayout 

<declare-styleable name="ExpandTextView" 
<attr name="showLines" format="integer"/ 
</declare-styleable 

<mo.yumf.com.myviews.ExpandTextView
android:id="@+id/expandTextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:showLines="4"/