如何在 Android 中创建分页文本？

这个例子演示了如何在 Android 中创建分页文本。

步骤 1 − 在 Android Studio 中创建一个新项目，转到文件 ⇒ 新项目并填写所有必需的详细信息以创建一个新项目。

步骤 2 − 将以下代码添加到 res/layout/activity_main.xml 中。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:paddingLeft="16dp"
   android:paddingTop="16dp"
   android:paddingRight="16dp"
   android:paddingBottom="16dp">
   <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent">
      <Button
         android:id="@+id/btn_back"
         style="?android:attr/buttonBarButtonStyle"
         android:layout_width="0dp"
         android:layout_height="match_parent"
         android:layout_weight="1"
         android:background="@android:color/transparent" />
      <Button
         android:id="@+id/btn_forward"
         style="?android:attr/buttonBarButtonStyle"
         android:layout_width="0dp"
         android:layout_height="match_parent"
         android:layout_weight="1"
         android:background="@android:color/transparent" />
   </LinearLayout>
   <TextView
      android:id="@+id/tv"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />
</RelativeLayout>

步骤 3 − 将以下代码添加到 src/MainActivity.java 中

package app.com.sample;
import android.graphics.Color;
import android.graphics.Typeface;
import android.os.Bundle;
import android.text.Html;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.Spanned;
import android.text.TextUtils;
import android.text.style.ForegroundColorSpan;
import android.text.style.RelativeSizeSpan;
import android.text.style.StyleSpan;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
   private TextView mTextView;
   private Pagination mPagination;
   private CharSequence mText;
   private int mCurrentIndex = 0;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mTextView = findViewById(R.id.tv);
      Spanned htmlString = Html.fromHtml(getString(R.string.html_string));
      Spannable spanString = new SpannableString(getString(R.string.long_string));
      spanString.setSpan(new ForegroundColorSpan(Color.BLUE), 0, 24, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      spanString.setSpan(new RelativeSizeSpan(2f), 0, 24, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      spanString.setSpan(new StyleSpan(Typeface.MONOSPACE.getStyle()), 0, 24, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      spanString.setSpan(new ForegroundColorSpan(Color.BLUE), 700, spanString.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      spanString.setSpan(new RelativeSizeSpan(2f), 700, spanString.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      spanString.setSpan(new StyleSpan(Typeface.MONOSPACE.getStyle()), 700, spanString.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      mText = TextUtils.concat(htmlString, spanString);
      mTextView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
         @Override
         public void onGlobalLayout() {
            // Removing layout listener to avoid multiple calls
            mTextView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
            mPagination = new Pagination(
               mText, mTextView.getWidth(),
               mTextView.getHeight(),
               mTextView.getPaint(),
               mTextView.getLineSpacingMultiplier(),
               mTextView.getLineSpacingExtra(),
               mTextView.getIncludeFontPadding());
            update();
         }
      });
      findViewById(R.id.btn_back).setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view) {
            mCurrentIndex = (mCurrentIndex > 0) ? mCurrentIndex - 1 : 0;
            update();
         }
      });
      findViewById(R.id.btn_forward).setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view) {
            mCurrentIndex = (mCurrentIndex < mPagination.size() - 1) ? mCurrentIndex + 1 : mPagination.size() - 1;
            update();
         }
      });
   }  
   private void update() {
      final CharSequence text = mPagination.get(mCurrentIndex);
      if (text != null) mTextView.setText(text);
   }
}

步骤 4 − 将以下代码添加到 src/Pagination.java 中

package app.com.sample;
import android.text.Layout;
import android.text.StaticLayout;
import android.text.TextPaint;
import java.util.ArrayList;
import java.util.List;
class Pagination {
   private final boolean mIncludePad;
   private final int mWidth;
   private final int mHeight;
   private final float mSpacingMult;
   private final float mSpacingAdd;
   private final CharSequence mText;
   private final TextPaint mPaint;
   private final List<CharSequence> mPages;
   Pagination(CharSequence text, int pageW, int pageH, TextPaint paint, float spacingMult, float spacingAdd, boolean inclidePad) {
      this.mText = text;
      this.mWidth = pageW;
      this.mHeight = pageH;
      this.mPaint = paint;
      this.mSpacingMult = spacingMult;
      this.mSpacingAdd = spacingAdd;
      this.mIncludePad = inclidePad;
      this.mPages = new ArrayList<>();
      layout();
   }
   private void layout() {
      final StaticLayout layout = new StaticLayout(mText, mPaint, mWidth, Layout.Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, mIncludePad);
      final int lines = layout.getLineCount();
      final CharSequence text = layout.getText();
      int startOffset = 0;
      int height = mHeight;
      for (int i = 0; i < lines; i++) {
         if (height < layout.getLineBottom(i)) {
            // When the layout height has been exceeded
            addPage(text.subSequence(startOffset, layout.getLineStart(i)));
            startOffset = layout.getLineStart(i);
            height = layout.getLineTop(i) + mHeight;
         }
         if (i == lines - 1) {
            // Put the rest of the text into the last page
            addPage(text.subSequence(startOffset, layout.getLineEnd(i)));
            return;
         }
      }
   }
   private void addPage(CharSequence text) {
      mPages.add(text);
   }
   int size() {
      return mPages.size();
   }
   CharSequence get(int index) {
      return (index >= 0 && index < mPages.size()) ? mPages.get(index) : null;
   }
}

步骤 5 − 将以下代码添加到 androidManifest.xml 中

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

让我们尝试运行你的应用程序。我假设你已经将你的实际 Android 移动设备连接到你的电脑。要从 Android Studio 运行该应用程序，请打开该项目的一个活动文件，然后单击工具栏中运行图标。选择你的移动设备作为选项，然后检查你的移动设备，它将显示你的默认屏幕 −