本文介绍一个这样婶儿的TextView，如图：
点击的时候TextView会伸缩，有种Clip的感觉，原理也很简单，就是把两个TextView重叠起来，一个现实固定的行数的文本，另一个现实全部的文本，初始化的时候，容器的高度等于固定文本的高度，完全展开时的高度等于文本显示全的高度，过程用一个动画控制就可以了。下面贴代码：
import android.content.Context;
import android.graphics.Color;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.FrameLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;
/**
* Created by mingwei on 1/20/16.
*/
public class ExpandTextView extends RelativeLayout {
private TextView mText;
private TextView mExpandText;
private int mTextColor = Color.GRAY;
private int mTextLine = 1;
private int mStart;
private int mEnd;
private boolean isFirst = true;
private boolean isExpand = false;
public ExpandTextView(Context context) {
this(context, null);
}
public ExpandTextView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
final ViewGroup.LayoutParams params = getLayoutParams();
if (isFirst) {
isFirst = false;
mText.post(new Runnable() {
@Override
public void run() {
mStart = mText.getLineHeight() * mText.getLineCount();
params.height = mStart;
setLayoutParams(params);
}
});
mExpandText.post(new Runnable() {
@Override
public void run() {
mEnd = mExpandText.getLineHeight() * mExpandText.getLineCount();
}
});
}
}
public ExpandTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.WRAP_CONTENT);
mText = new TextView(context, attrs);
mText.setTextColor(mTextColor);
mText.setEllipsize(TextUtils.TruncateAt.END);
mText.setMaxLines(mTextLine);
addView(mText, params);
mExpandText = new TextView(context);
mExpandText.setTextColor(Color.TRANSPARENT);
addView(mExpandText, params);
}
public void setText(String text) {
isFirst = true;
mText.setText(text);
mExpandText.setText(text);
requestLayout();
}
public void setTextColor(int color) {
mTextColor = color;
mText.setTextColor(color);
}
public void setTextSize(int size) {
isFirst = true;
mText.setTextSize(size);
mExpandText.setTextSize(size);
requestLayout();
}
public void setTextMaxLine(int num) {
mTextLine = num;
mText.setMaxLines(num);
}
public void setGravity(int gravity) {
mText.setGravity(gravity);
mExpandText.setGravity(gravity);
}
public void setEllipsize(TextUtils.TruncateAt ell) {
mText.setEllipsize(ell);
}
public void setTextLineSpacingExtra(float spac) {
mText.setLineSpacing(spac, 1.0f);
mExpandText.setLineSpacing(spac, 1.0f);
}
public TextView text() {
return mText;
}
public TextView expandText() {
return mExpandText;
}
public int line() {
return mTextLine;
}
public boolean isExpand() {
return isExpand;
}
public void expand() {
if (!isExpand) {
isExpand = true;
mText.setTextColor(Color.TRANSPARENT);
mExpandText.setTextColor(mTextColor);
Animation animation = new Animation() {
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
ViewGroup.LayoutParams params = ExpandTextView.this.getLayoutParams();
params.height = mStart + (int) ((mEnd - mStart) * interpolatedTime);
setLayoutParams(params);
}
};
animation.setDuration(500);
startAnimation(animation);
}
}
@Override
public void setLayoutParams(ViewGroup.LayoutParams params) {
super.setLayoutParams(params);
}
public void shrink() {
if (isExpand) {
isExpand = false;
Animation animation = new Animation() {
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
ViewGroup.LayoutParams params = ExpandTextView.this.getLayoutParams();
params.height = mStart + (int) ((mEnd - mStart) * (1 - interpolatedTime));
setLayoutParams(params);
}
};
animation.setAnimationListener(new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
}
@Override
public void onAnimationEnd(Animation animation) {
mText.setTextColor(mTextColor);
mExpandText.setTextColor(Color.TRANSPARENT);
}
@Override
public void onAnimationRepeat(Animation animation) {
}
});
animation.setDuration(500);
startAnimation(animation);
}
}
public void switchs() {
if (isExpand) {
shrink();
} else {
expand();
}
}
}
使用：
<?xml version="1.0" encoding="utf-8"?>
<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.ming.expandtextview.MainActivity">
<Button
android:id="@+id/expand"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:text="Expand" />
<Button
android:id="@+id/strink"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_toEndOf="@+id/expand"
android:layout_toRightOf="@+id/expand"
android:text="Strink" />
<com.ming.expandtextview.ExpandTextView
android:id="@+id/expandtextview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/expand">
</com.ming.expandtextview.ExpandTextView>
</RelativeLayout>
Activity.java
public class MainActivity extends AppCompatActivity {
private Button mBtnExpand;
private Button mBtnStrink;
private ExpandTextView mExpandTextview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mBtnExpand = (Button) findViewById(R.id.expand);
mBtnStrink = (Button) findViewById(R.id.strink);
mExpandTextview = (ExpandTextView) findViewById(R.id.expandtextview);
mExpandTextview.setTextColor(Color.BLACK);
mExpandTextview.setTextSize(18);
mExpandTextview.setTextMaxLine(2);
mExpandTextview.setText("科技本身蕴含着一种碾压一切的力量，而这种力量会导致我们加速奔向某种设定好的结局。" +
"这篇文章尝试预测未来最可能的5种结局：黄金时代，虚拟世界，冷平衡，生化人，大寂灭。");
mBtnExpand.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mExpandTextview.expand();
//或者mExpandTextview.switchs();
}
});
mBtnStrink.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mExpandTextview.shrink();
}
});
}
}
