使用WebView开发的坑很多，这是众所周知的。本文分别对WebView的三个基本控件（俗称三剑客WebViewClient，WebChromeClient,WebView）做了一些封装，方便使用，避免掉坑里。
主要有以下功能：
- 自定义出错页面，并实现重新加载事件
- 全屏播放视频
- 封装更加简单易用生命周期api，使用这些生命周期的方法可以避免很多与H5交互的坑
- 封装调用JS的方法，可以方便获取JS执行的返回值
在WebViewClient中主要是对onReceivedError方法进行重写。这里面的逻辑这样的：
- 出错的url如果跟打开的url是一样的，那么这个时候显示自定义的出错页面。这个自定义页面是一个本地静态html。放在assets目录下。
- 如果这个出错的url就是本地的静态文件，那么也显示自定义访问出错页面。
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
if (view == null) {
return; // 极端情况下可能出现，加个保险
}
boolean isMainFrame = view.getUrl() != null && view.getUrl().equals(failingUrl);
String url = view.getUrl();
//这判断非常重要，避免打开一个页面时，显示出来了内容，然后有被重定向到一个无效地址
if (isMainFrame || url.equalsIgnoreCase(CustomWebView.CUSTOM_ERROR_PAGE)) {//或者加载本地时也发生错误
if (view instanceof CustomWebView) {
((CustomWebView) view).onErrorView(url);
}
} else {
Log.d(TAG, "did not show error view! reload url:" + view.getUrl());
}
Log.d(TAG, "onReceivedError-> errorCode=" + errorCode + ",desc=" + description + ",failingUrl=" + failingUrl);
}在这里主要是实现视频全屏播放的逻辑，重写onShowCustomView()和onHideCustomView()方法
@Override
public void onShowCustomView(View view, CustomViewCallback callback) {
if (view == null) {
return;
}
mActivity = AppUtils.getCurrActivity(view.getContext());
Activity activity = mActivity;
if (activity == null || activity.isFinishing()) {
LogUtils.e("must use activity context to show video view!");
return;
}
if (mCustomView != null && callback != null) {
callback.onCustomViewHidden();
return;
}
try {
view.setKeepScreenOn(true);
} catch (SecurityException e) {
LogUtils.d("WebView is not allowed to keep the screen on");
}
mOriginalOrientation = activity.getRequestedOrientation();
FrameLayout decor = (FrameLayout) activity.getWindow().getDecorView();
mFullscreenContainer = new FrameLayout(activity.getApplicationContext());
// mFullscreenContainer.setBackgroundColor(ContextCompat.getColor(activity.getApplicationContext(), android.R.color.black));
mCustomView = view;
mFullscreenContainer.addView(mCustomView, COVER_SCREEN_PARAMS);
decor.addView(mFullscreenContainer, COVER_SCREEN_PARAMS);
activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
setFullscreen(true, true);
// mCurrentView.setVisibility(View.GONE);
if (view instanceof FrameLayout) {
if (((FrameLayout) view).getFocusedChild() instanceof VideoView) {
mVideoView = (VideoView) ((FrameLayout) view).getFocusedChild();
mVideoView.setOnErrorListener(new VideoCompletionListener());
mVideoView.setOnCompletionListener(new VideoCompletionListener());
}
}
mCustomViewCallback = callback;
}
@Override
public void onHideCustomView() {
if (mCustomView == null || mCustomViewCallback == null) {
return;
}
LogUtils.d("onHideCustomView");
// mCurrentView.setVisibility(View.VISIBLE);
try {
mCustomView.setKeepScreenOn(false);
} catch (SecurityException e) {
LogUtils.d("WebView is not allowed to keep the screen on");
}
setFullscreen(false, false);
Activity activity = mActivity;
if (activity == null || activity.isFinishing()) {
return;
}
FrameLayout decor = (FrameLayout) activity.getWindow().getDecorView();
if (decor != null) {
decor.removeView(mFullscreenContainer);
}
if (API < Build.VERSION_CODES.KITKAT) {
try {
mCustomViewCallback.onCustomViewHidden();
} catch (Throwable ignored) {
}
}
mFullscreenContainer = null;
mCustomView = null;
if (mVideoView != null) {
mVideoView.setOnErrorListener(null);
mVideoView.setOnCompletionListener(null);
mVideoView = null;
}
activity.setRequestedOrientation(mOriginalOrientation);
mActivity = null;
}在CustomWebView中封装了生命周期方法，resume(),pause(),destroy() 这几个方法对应于Activity或者Fragment中的生命周期方法。同时还自定义访问出错页面。
有了以上三个基本控件的封装，那么使用起来就非常简单了。
public class WebViewActivity extends AppCompatActivity {
...
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web_view);
...
mWebView.loadUrl(url);
mWebView.setWebViewClient(new CustomWebViewClient());
mWebView.setWebChromeClient(new CustomWebChromeClient() {
@Override
public void onProgressChanged(WebView view, int newProgress) {
super.onProgressChanged(view, newProgress);
mProgressBar.setProgress(newProgress);
mProgressBar.setVisibility(newProgress >= 100 ? View.GONE : View.VISIBLE);
}
});
}
...
@Override
protected void onPause() {
super.onPause();
mWebView.pause();
}
@Override
protected void onResume() {
super.onResume();
mWebView.resume();
}
}由于WebViewActivity中有实现视频全屏播放的功能，那么在CustomWebView中的初始化中需要对WebView作以下配置
void settings() {
WebSettings setting = getSettings();
setting.setJavaScriptEnabled(true);
setting.setJavaScriptCanOpenWindowsAutomatically(true);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
setting.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
}
setting.setJavaScriptCanOpenWindowsAutomatically(true);
setting.setAllowFileAccess(false);
// setting.setAllowFileAccessFromFileURLs(true);
setting.setBuiltInZoomControls(false);
setting.setSupportZoom(false);
setting.setDisplayZoomControls(false);
setting.setSaveFormData(false);
setting.setLayoutAlgorithm(WebSettings.LayoutAlgorithm.NARROW_COLUMNS);
setting.setCacheMode(WebSettings.LOAD_NO_CACHE);// 不使用缓存
setting.setDefaultTextEncodingName("UTF-8");
setting.setRenderPriority(WebSettings.RenderPriority.HIGH);
// 自适应屏幕
setting.setUseWideViewPort(true);
setting.setLoadWithOverviewMode(true);
setting.setDomStorageEnabled(true);//应该设置为true，否则视频的缩略图会被放大
}以上配置都在实际开发中得到验证的，一般来说，这样配置是可以满足很多需求的。
另外如果需要显示全屏，那么需要在WebViewActivity的manifiest中的configChanges属性配置如下:
<activity
android:name=".WebViewActivity"
android:label="Web"
android:configChanges="orientation|screenSize|keyboardHidden"
android:screenOrientation="portrait"/>