900字范文 > Android 自定义WebView 实现可以加载缓存数据

Android 自定义WebView 实现可以加载缓存数据

时间：2022-10-01 00:43:18

1.自定义WebView说明

1.1.这个WebView可以加载缓存的数据。（需要后端配合，将html转换成一个字符串，主要是图片要用特殊格式）

1.2.注入了图片链接，为了方便点击webView中的图片而跳转。

1.3.这是一个FrameLayout动态加载的WebView，布局中没有任何声明这个WebView。

2.源代码及应用

2.1.源代码如下，可以直接Copy。

public class MarkdownView extends WebView {private static final String TAG = MarkdownView.class.getSimpleName();// 带有点击的图片 => 为了防止被转换，提前转化为 html// [text ![text](image_url) text](link) => <a href="link" ><img src="image_url" /></a>private static final String IMAGE_LINK_PATTERN = "\\[(.*)!\\[(.*)\\]\$(.*)\$(.*)\\]\$(.*)\$";private static final String IMAGE_LINK_REPLACE = "<a href=\"$5\" >$1<img src=\"$3\" />$4</a>";// 纯图片 => 添加点击跳转，方便后期拦截// ![text](image_url) => <img class="gcs-img-sign" src="image_url" />private static final String IMAGE_PATTERN = "!\\[(.*)\\]\$(.*)\$";private static final String IMAGE_REPLACE = "<img class=\"gcs-img-sign\" src=\"$2\" />";private String mPreviewText;public MarkdownView(Context context) {this(context, null);}public MarkdownView(Context context, AttributeSet attrs) {this(context, attrs, 0);}@SuppressLint({"AddJavascriptInterface", "SetJavaScriptEnabled"})public MarkdownView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);if (isInEditMode()) {return;}WebSettings settings = getSettings();settings.setJavaScriptEnabled(true);settings.setDomStorageEnabled(true);settings.setDatabaseEnabled(true);initialize();}private void initialize() {loadUrl("file:///android_asset/html/preview.html");if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {getSettings().setAllowUniversalAccessFromFileURLs(true);}if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {getSettings().setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);}setWebChromeClient(new WebChromeClient() {@SuppressLint("JavascriptInterface")@Overridepublic void onProgressChanged(WebView view, int newProgress) {super.onProgressChanged(view, newProgress);if (newProgress == 100) {if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {loadUrl(mPreviewText);} else {evaluateJavascript(mPreviewText, null);}}}});}public void loadMarkdownFromFile(File markdownFile) {String mdText = "";try {FileInputStream fileInputStream = new FileInputStream(markdownFile);InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);BufferedReader bufferedReader = new BufferedReader(inputStreamReader);String readText;StringBuilder stringBuilder = new StringBuilder();while ((readText = bufferedReader.readLine()) != null) {stringBuilder.append(readText);stringBuilder.append("\n");}fileInputStream.close();mdText = stringBuilder.toString();} catch (FileNotFoundException e) {Log.e(TAG, "FileNotFoundException:" + e);} catch (IOException e) {Log.e(TAG, "IOException:" + e);}setMarkDownText(mdText);}public void loadMarkdownFromAssets(String assetsFilePath) {try {StringBuilder buf = new StringBuilder();InputStream json = getContext().getAssets().open(assetsFilePath);BufferedReader in = new BufferedReader(new InputStreamReader(json, "UTF-8"));String str;while ((str = in.readLine()) != null) {buf.append(str).append("\n");}in.close();setMarkDownText(buf.toString());} catch (IOException e) {e.printStackTrace();}}public void setMarkDownText(String markdownText) {String injectMdText = injectImageLink(markdownText);String escMdText = escapeForText(injectMdText);if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {mPreviewText = String.format("javascript:preview('%s')", escMdText);} else {mPreviewText = String.format("preview('%s')", escMdText);}initialize();}/*** 注入图片链接*/private String injectImageLink(String mdText) {// TODO 修复代码区md格式图片被替换问题mdText = mdText.replaceAll(IMAGE_LINK_PATTERN, IMAGE_LINK_REPLACE);mdText = mdText.replaceAll(IMAGE_PATTERN, IMAGE_REPLACE);return mdText;}private String escapeForText(String mdText) {String escText = mdText.replace("\n", "\\\\n");escText = escText.replace("'", "\\\'");escText = escText.replace("\r", "");return escText;}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);if (isInEditMode()) {canvas.drawColor(Color.WHITE);canvas.translate(canvas.getWidth() / 2, 30);Paint paint = new Paint();paint.setTextAlign(Paint.Align.CENTER);paint.setTextSize(30);paint.setColor(Color.GRAY);canvas.drawText("MarkdownView", -30, 0, paint);}}}

View Code

2.2.然后如何动态加载WebView。

2.3.从缓存中获取字符串

这个body就是一些缓存的数据了。还要进行转换才能得到html。