Question

我一直在使用一个电子阅读器，它使用一个android TextView在屏幕上勾选一个epub的章节。当章节少于~2300个字符（不常见）时，这种方法很有效，但是当章节较长时，会开始加扰我的文本。结果如下所示：image of scrambled chapter text。在这里，您可以看到我的字符串的开头与字符串的中间重叠

import android.content.Context;
import android.graphics.Rect;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.view.animation.LinearInterpolator;
import android.widget.Scroller;
import android.widget.TextView;

public class ScrollTextView extends TextView {

    // scrolling feature
    private Scroller mSlr;

    // milliseconds for a round of scrolling
    private int mRndDuration = 250;

    // the X offset when paused
    private int mXPaused = 0;

    // whether it's being paused
    private boolean mPaused = true;

    /*
     * constructor
     */
    public ScrollTextView(Context context) {
        this(context, null);
    }

    /*
     * constructor
     */
    public ScrollTextView(Context context, AttributeSet attrs) {
        this(context, attrs, android.R.attr.textViewStyle);
    }

    /*
     * constructor
     */
    public ScrollTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // customize the TextView
        setSingleLine();
        setEllipsize(null);
        setVisibility(INVISIBLE);
    }

    /**
     * begin to scroll the text from the original position
     */
    public void startScroll() {
        // begin from the very right side
        mXPaused = -1 * getWidth();
        // assume it's paused
        mPaused = true;
        resumeScroll();
    }

    /**
     * resume the scroll from the pausing point
     */
    public void resumeScroll() {

        if (!mPaused) {
            return;
        }

        // Do not know why it would not scroll sometimes
        // if setHorizontallyScrolling is called in constructor.
        setHorizontallyScrolling(true);

        // use LinearInterpolator for steady scrolling
        mSlr = new Scroller(this.getContext(), new LinearInterpolator());
        setScroller(mSlr);

        int scrollingLen = calculateScrollingLen();
        int distance = scrollingLen - (getWidth() + mXPaused);
        int duration = (new Double(mRndDuration * distance * 1.00000
                / scrollingLen)).intValue();

        setVisibility(VISIBLE);
        mSlr.startScroll(mXPaused, 0, distance, 0, duration);
        mPaused = false;
    }

    /**
     * calculate the scrolling length of the text in pixel
     *
     * @return the scrolling length in pixels
     */
    private int calculateScrollingLen() {
        TextPaint tp = getPaint();
        Rect rect = new Rect();
        String strTxt = getText().toString();
        tp.getTextBounds(strTxt, 0, strTxt.length(), rect);
        int scrollingLen = rect.width() + getWidth();
        rect = null;
        return scrollingLen;
    }

    /**
     * pause scrolling the text
     */
    public void pauseScroll() {
        if (null == mSlr) {
            return;
        }

        if (mPaused) {
            return;
        }

        mPaused = true;

        // abortAnimation sets the current X to be the final X,
        // and sets isFinished to be true
        // so current position shall be saved
        mXPaused = mSlr.getCurrX();

        mSlr.abortAnimation();
    }

    /*
     * override the computeScroll to restart scrolling when finished so as that
     * the text is scrolled forever
     */
    @Override
    public void computeScroll() {
        super.computeScroll();

        if (null == mSlr) {
            return;
        }

        if (mSlr.isFinished() && (!mPaused)) {
            this.startScroll();
        }
    }

    public int getRndDuration() {
        return mRndDuration;
    }

    public void setRndDuration(int duration) {
        this.mRndDuration = duration;
    }

    public boolean isPaused() {
        return mPaused;
    }
}

任何帮助或见解将不胜感激。我很好奇，如果这只是对Android TextView的不当使用，也许我应该使用OpenGL。

update1：增加文本大小会使加扰更快启动。减少它恰恰相反。

Update2：当字体为32pt时滚动~2300个字符后的字符串加扰

更新3：澄清this is what it looks like while it's scrolling

Answer 1

为什么不在TextView -

中使用ScrollView

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Your long text goes here..." />
</ScrollView>

如果您需要动态设置文本，也可以使用setText()

TextView textView = (TextView) findViewById(R.id.text);
textView.setText("Your long text goes here...");

当字符串太大时，有没有办法避免Android Textview加扰？

1 个答案: