Question

如何让TextView跟着RecyclerView滚动

Answer 1

下面看看主要代码：
1、创建一个类继承TextView
/**
* @author xushilin
*
* 垂直滚动的TextView Widget
*/
public class VerticalScrollTextView extends TextView

2、实现构造函数：
public VerticalScrollTextView(Context context) {
super(context);
init();
}
public VerticalScrollTextView(Context context, AttributeSet attr) {
super(context, attr);
init();
}
public VerticalScrollTextView(Context context, AttributeSet attr, int i) {
super(context, attr, i);
init();
}
private void init() {
setFocusable(true);
//这里主要处理如果没有传入内容显示的默认值
if(list==null){
list=new ArrayList();
Notice sen=new Notice(0,"暂时没有通知公告");
list.add(0, sen);
}
//普通文字的字号，以及画笔颜色的设置
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setTextSize(16);
mPaint.setColor(Color.BLACK);
mPaint.setTypeface(Typeface.SERIF);
//高亮文字的字号，以及画笔颜色的设置
mPathPaint = new Paint();
mPathPaint.setAntiAlias(true);
mPathPaint.setColor(Color.RED);
mPathPaint.setTextSize(16);
mPathPaint.setTypeface(Typeface.SANS_SERIF);
}

3、从写onDraw方法，并计算文字的行距，并且将将普通文字和高亮文字，在这个方法中绘制出来
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(0xEFeffff);
Paint p = mPaint;
Paint p2 = mPathPaint;
p.setTextAlign(Paint.Align.CENTER);
if (index == -1)
return;
p2.setTextAlign(Paint.Align.CENTER);

canvas.drawText(list.get(index).getName(), mX, middleY, p2);
float tempY = middleY;

for (int i = index - 1; i >= 0; i--) {
tempY = tempY - DY;
if (tempY < 0) {
break;
}
canvas.drawText(list.get(i).getName(), mX, tempY, p);
}
tempY = middleY;

for (int i = index + 1; i < list.size(); i++) {
tempY = tempY + DY;
if (tempY > mY) {
break;
}
canvas.drawText(list.get(i).getName(), mX, tempY, p);
}
}
4、计算Y轴中值以及更新索引
protected void onSizeChanged(int w, int h, int ow, int oh) {
super.onSizeChanged(w, h, ow, oh);
mX = w * 0.5f;
mY = h;
middleY = h * 0.5f;
}

private long updateIndex(int index) {
if (index == -1)
return -1;
this.index=index;
return index;
}

5、定时更新view，并将接口暴露给客户程序调用。
public void updateUI(){
new Thread(new updateThread()).start();
}

class updateThread implements Runnable {
long time = 1000;
int i=0;
public void run() {
while (true) {
long sleeptime = updateIndex(i);
time += sleeptime;
mHandler.post(mUpdateResults);
if (sleeptime == -1)
return;
try {
Thread.sleep(time);
i++;
if(i==getList().size())
i=0;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
Handler mHandler = new Handler();
Runnable mUpdateResults = new Runnable() {
public void run() {
invalidate();
}
};

6、xml布局文件中调用：

<LinearLayout xmlns:android="
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">

<com.demo.xsl.text.SampleView
android:id="@+id/sampleView1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/selector"
/>

7、java代码中调用，传递数据：
package com.demo.xsl.text;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;

public class VerticalScrollTextActivity extends Activity {

SampleView mSampleView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mSampleView = (SampleView) findViewById(R.id.sampleView1);
List lst=new ArrayList();
for(int i=0;i<30;i++){
if(i%2==0){
Sentence sen=new Sentence(i,i+"、金球奖三甲揭晓 C罗梅西哈维入围 ");
lst.add(i, sen);
}else{
Sentence sen=new Sentence(i,i+"、公牛欲用三大主力换魔兽？？？？？");
lst.add(i, sen);
}
}
//给View传递数据
mSampleView.setList(lst);
//更新View
mSampleView.updateUI();
}
}