我正在尝试在Android应用中自动滚动。
假设我有这样的xml代码：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="show me the texts"
android:id="@+id/button"/>
<ScrollView
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/text"
android:id="@+id/textView1"/>
</ScrollView>
</LinearLayout>
在这个xml代码中，我在屏幕顶部有一个Button，还有一个由ScrollView包装的TextView。这意味着我的TextView现在可以滚动。
它工作正常，因为当用户触摸屏幕并向下或向上交换时，TextView可以上下滚动。
但是...
我打算有一个Auto Scrollable TextView，而且我自己的意思是，我需要一个可滚动的TextView，在10秒后向下滚动大约10dp。
我知道我必须在我的应用程序中使用一些线程来计算时间，但我不知道怎么说TextView在10秒后向下滚动。例如。
有什么建议吗？任何提示将不胜感激。感谢
答案 0 :(得分：2)
您可以使用以下内容：
mScrollView.post(new Runnable() {
public void run() {
mScrollView.smoothScrollBy(10, 10);
}
});
smoothScrollBy的文档：http://developer.android.com/reference/android/widget/ScrollView.html#smoothScrollBy(int,int)
每10秒执行一次此任务：
TimerTask fileProcessTask = new TimerTask(){
@Override
public void run() {
//Scrolling here
}
};
Timer tm = new Timer();
tm.schedule(fileProcessTask, 10000L);
另请看一下这篇SO帖子：https://stackoverflow.com/a/14685729/3326331，我还没试过，但你可以尝试一下。
答案 1 :(得分：0)
创建一个新的类文件并粘贴下面的代码。
在您的Layout.xml中，请参考EllipsizingTextView，而不是使用Android TextView。
/*
* Copyright (C) 2011 Micah Hainline
* Copyright (C) 2012 Triposo
* Copyright (C) 2013 Paul Imhoff
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.text.Layout;
import android.text.Layout.Alignment;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.StaticLayout;
import android.text.TextUtils;
import android.text.TextUtils.TruncateAt;
import android.util.AttributeSet;
import android.widget.TextView;
/**
* A {@link android.widget.TextView} that ellipsizes more intelligently. This class supports ellipsizing multiline text through setting {@code android:ellipsize} and {@code android:maxLines}.
*/
public class EllipsizingTextView extends TextView {
private static final CharSequence ELLIPSIS = "\u2026";
private static final Pattern DEFAULT_END_PUNCTUATION = Pattern.compile("[\\.!?,;:\u2026]*$", Pattern.DOTALL);
private final List<EllipsizeListener> mEllipsizeListeners = new ArrayList<EllipsizeListener>();
private EllipsizeStrategy mEllipsizeStrategy;
private boolean isEllipsized;
private boolean isStale;
private boolean programmaticChange;
private CharSequence mFullText;
private int mMaxLines;
private float mLineSpacingMult = 1.0f;
private float mLineAddVertPad = 0.0f;
/**
* The end punctuation which will be removed when appending {@link #ELLIPSIS}.
*/
private Pattern mEndPunctPattern;
public EllipsizingTextView(Context context) {
this(context, null);
}
public EllipsizingTextView(Context context, AttributeSet attrs) {
this(context, attrs, android.R.attr.textViewStyle);
}
public EllipsizingTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.obtainStyledAttributes(attrs, new int[] { android.R.attr.maxLines, android.R.attr.ellipsize }, defStyle, 0);
setMaxLines(a.getInt(0, Integer.MAX_VALUE));
a.recycle();
setEndPunctuationPattern(DEFAULT_END_PUNCTUATION);
}
public void setEndPunctuationPattern(Pattern pattern) {
mEndPunctPattern = pattern;
}
public void addEllipsizeListener(EllipsizeListener listener) {
if (listener == null)
throw new NullPointerException();
mEllipsizeListeners.add(listener);
}
public void removeEllipsizeListener(EllipsizeListener listener) {
mEllipsizeListeners.remove(listener);
}
public boolean isEllipsized() {
return isEllipsized;
}
/**
* @return The maximum number of lines displayed in this {@link android.widget.TextView}.
*/
@SuppressLint("Override")
public int getMaxLines() {
return mMaxLines;
}
@Override
public void setMaxLines(int maxLines) {
super.setMaxLines(maxLines);
mMaxLines = maxLines;
isStale = true;
}
@Override
public boolean isFocused() {
return true;
}
/**
* Determines if the last fully visible line is being ellipsized.
*
* @return {@code true} if the last fully visible line is being ellipsized; otherwise, returns {@code false}.
*/
public boolean ellipsizingLastFullyVisibleLine() {
return mMaxLines == Integer.MAX_VALUE;
}
@Override
public void setLineSpacing(float add, float mult) {
mLineAddVertPad = add;
mLineSpacingMult = mult;
super.setLineSpacing(add, mult);
}
@Override
public void setText(CharSequence text, BufferType type) {
if (!programmaticChange) {
mFullText = text;
isStale = true;
}
super.setText(text, type);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (ellipsizingLastFullyVisibleLine())
isStale = true;
}
@Override
public void setPadding(int left, int top, int right, int bottom) {
super.setPadding(left, top, right, bottom);
if (ellipsizingLastFullyVisibleLine())
isStale = true;
}
@Override
protected void onDraw(Canvas canvas) {
if (isStale)
resetText();
super.onDraw(canvas);
}
/**
* Sets the ellipsized text if appropriate.
*/
private void resetText() {
int maxLines = getMaxLines();
CharSequence workingText = mFullText;
boolean ellipsized = false;
if (maxLines != -1) {
if (mEllipsizeStrategy == null)
setEllipsize(null);
workingText = mEllipsizeStrategy.processText(mFullText);
ellipsized = !mEllipsizeStrategy.isInLayout(mFullText);
}
if (!workingText.equals(getText())) {
programmaticChange = true;
try {
setText(workingText);
} finally {
programmaticChange = false;
}
}
isStale = false;
if (ellipsized != isEllipsized) {
isEllipsized = ellipsized;
for (EllipsizeListener listener : mEllipsizeListeners) {
listener.ellipsizeStateChanged(ellipsized);
}
}
}
/**
* Causes words in the text that are longer than the view is wide to be ellipsized instead of broken in the middle. Use {@code null} to turn off ellipsizing.
*
* @param where
* part of text to ellipsize
*/
@Override
public void setEllipsize(TruncateAt where) {
if (where == null) {
mEllipsizeStrategy = new EllipsizeNoneStrategy();
return;
}
switch (where) {
case END:
mEllipsizeStrategy = new EllipsizeEndStrategy();
break;
case START:
mEllipsizeStrategy = new EllipsizeStartStrategy();
break;
case MIDDLE:
mEllipsizeStrategy = new EllipsizeMiddleStrategy();
break;
case MARQUEE:
super.setEllipsize(where);
isStale = false;
default:
mEllipsizeStrategy = new EllipsizeNoneStrategy();
break;
}
}
/**
* A listener that notifies when the ellipsize state has changed.
*/
public interface EllipsizeListener {
void ellipsizeStateChanged(boolean ellipsized);
}
/**
* A base class for an ellipsize strategy.
*/
private abstract class EllipsizeStrategy {
/**
* Returns ellipsized text if the text does not fit inside of the layout; otherwise, returns the full text.
*
* @param text
* text to process
* @return Ellipsized text if the text does not fit inside of the layout; otherwise, returns the full text.
*/
public CharSequence processText(CharSequence text) {
return !isInLayout(text) ? createEllipsizedText(text) : text;
}
/**
* Determines if the text fits inside of the layout.
*
* @param text
* text to fit
* @return {@code true} if the text fits inside of the layout; otherwise, returns {@code false}.
*/
public boolean isInLayout(CharSequence text) {
Layout layout = createWorkingLayout(text);
return layout.getLineCount() <= getLinesCount();
}
/**
* Creates a working layout with the given text.
*
* @param workingText
* text to create layout with
* @return {@link android.text.Layout} with the given text.
*/
protected Layout createWorkingLayout(CharSequence workingText) {
return new StaticLayout(workingText, getPaint(), getWidth() - getCompoundPaddingLeft() - getCompoundPaddingRight(), Alignment.ALIGN_NORMAL, mLineSpacingMult, mLineAddVertPad, false /* includepad */);
}
/**
* Get how many lines of text we are allowed to display.
*/
protected int getLinesCount() {
if (ellipsizingLastFullyVisibleLine()) {
int fullyVisibleLinesCount = getFullyVisibleLinesCount();
return fullyVisibleLinesCount == -1 ? 1 : fullyVisibleLinesCount;
} else {
return mMaxLines;
}
}
/**
* Get how many lines of text we can display so their full height is visible.
*/
protected int getFullyVisibleLinesCount() {
Layout layout = createWorkingLayout("");
int height = getHeight() - getCompoundPaddingTop() - getCompoundPaddingBottom();
int lineHeight = layout.getLineBottom(0);
return height / lineHeight;
}
/**
* Creates ellipsized text from the given text.
*
* @param fullText
* text to ellipsize
* @return Ellipsized text
*/
protected abstract CharSequence createEllipsizedText(CharSequence fullText);
}
/**
* An {@link EllipsizingTextView.EllipsizeStrategy} that does not ellipsize text.
*/
private class EllipsizeNoneStrategy extends EllipsizeStrategy {
@Override
protected CharSequence createEllipsizedText(CharSequence fullText) {
return fullText;
}
}
/**
* An {@link EllipsizingTextView.EllipsizeStrategy} that ellipsizes text at the end.
*/
private class EllipsizeEndStrategy extends EllipsizeStrategy {
@Override
protected CharSequence createEllipsizedText(CharSequence fullText) {
Layout layout = createWorkingLayout(fullText);
int cutOffIndex = layout.getLineEnd(mMaxLines - 1);
int textLength = fullText.length();
int cutOffLength = textLength - cutOffIndex;
if (cutOffLength < ELLIPSIS.length())
cutOffLength = ELLIPSIS.length();
String workingText = TextUtils.substring(fullText, 0, textLength - cutOffLength).trim();
String strippedText = stripEndPunctuation(workingText);
while (!isInLayout(strippedText + ELLIPSIS)) {
int lastSpace = workingText.lastIndexOf(' ');
if (lastSpace == -1)
break;
workingText = workingText.substring(0, lastSpace).trim();
strippedText = stripEndPunctuation(workingText);
}
workingText = strippedText + ELLIPSIS;
SpannableStringBuilder dest = new SpannableStringBuilder(workingText);
if (fullText instanceof Spanned) {
TextUtils.copySpansFrom((Spanned) fullText, 0, workingText.length(), null, dest, 0);
}
return dest;
}
/**
* Strips the end punctuation from a given text according to {@link #mEndPunctPattern}.
*
* @param workingText
* text to strip end punctuation from
* @return Text without end punctuation.
*/
public String stripEndPunctuation(CharSequence workingText) {
return mEndPunctPattern.matcher(workingText).replaceFirst("");
}
}
/**
* An {@link EllipsizingTextView.EllipsizeStrategy} that ellipsizes text at the start.
*/
private class EllipsizeStartStrategy extends EllipsizeStrategy {
@Override
protected CharSequence createEllipsizedText(CharSequence fullText) {
Layout layout = createWorkingLayout(fullText);
int cutOffIndex = layout.getLineEnd(mMaxLines - 1);
int textLength = fullText.length();
int cutOffLength = textLength - cutOffIndex;
if (cutOffLength < ELLIPSIS.length())
cutOffLength = ELLIPSIS.length();
String workingText = TextUtils.substring(fullText, cutOffLength, textLength).trim();
while (!isInLayout(ELLIPSIS + workingText)) {
int firstSpace = workingText.indexOf(' ');
if (firstSpace == -1)
break;
workingText = workingText.substring(firstSpace, workingText.length()).trim();
}
workingText = ELLIPSIS + workingText;
SpannableStringBuilder dest = new SpannableStringBuilder(workingText);
if (fullText instanceof Spanned) {
TextUtils.copySpansFrom((Spanned) fullText, textLength - workingText.length(), textLength, null, dest, 0);
}
return dest;
}
}
/**
* An {@link EllipsizingTextView.EllipsizeStrategy} that ellipsizes text in the middle.
*/
private class EllipsizeMiddleStrategy extends EllipsizeStrategy {
@Override
protected CharSequence createEllipsizedText(CharSequence fullText) {
Layout layout = createWorkingLayout(fullText);
int cutOffIndex = layout.getLineEnd(mMaxLines - 1);
int textLength = fullText.length();
int cutOffLength = textLength - cutOffIndex;
if (cutOffLength < ELLIPSIS.length())
cutOffLength = ELLIPSIS.length();
cutOffLength += cutOffIndex % 2; // Make it even.
String firstPart = TextUtils.substring(fullText, 0, textLength / 2 - cutOffLength / 2).trim();
String secondPart = TextUtils.substring(fullText, textLength / 2 + cutOffLength / 2, textLength).trim();
while (!isInLayout(firstPart + ELLIPSIS + secondPart)) {
int lastSpaceFirstPart = firstPart.lastIndexOf(' ');
int firstSpaceSecondPart = secondPart.indexOf(' ');
if (lastSpaceFirstPart == -1 || firstSpaceSecondPart == -1)
break;
firstPart = firstPart.substring(0, lastSpaceFirstPart).trim();
secondPart = secondPart.substring(firstSpaceSecondPart, secondPart.length()).trim();
}
SpannableStringBuilder firstDest = new SpannableStringBuilder(firstPart);
SpannableStringBuilder secondDest = new SpannableStringBuilder(secondPart);
if (fullText instanceof Spanned) {
TextUtils.copySpansFrom((Spanned) fullText, 0, firstPart.length(), null, firstDest, 0);
TextUtils.copySpansFrom((Spanned) fullText, textLength - secondPart.length(), textLength, null, secondDest, 0);
}
return TextUtils.concat(firstDest, ELLIPSIS, secondDest);
}
}
}