WebView预加载
- 场景：
单Activity中有很多Fragment，Fragment中使用webview；如果不进行优化每次重新进入Fragmeng都会看到webview加载url的一个漫长过程； 避免这种情况，我的思路是：提前实例化webview，用一个容器将这些实例装起来，用到的时候取出来addView(WebView到布局中)；
- 先贴出使用代码，后边补充预加载相关类：
在MainActivity中初始化启动预加载：
private void preWebView(){
for (String url: Urls.getUrls()) {
if (url!=null){
WebViewTool.getInstance().putWebView(url,new MyWebView(mContext,url));
}
}
}
Fragmetn中使用webview；
public class WaterAnalysisFragment extends BaseFragment {
private String url = Api.IP + "wateranalysis";
@BindView(R.id.ll)
LinearLayout ll;
MyWebView webView;
@Override
protected int getLayoutId() {
return R.layout.water_frament_analysis;
}
public static WaterAnalysisFragment newInstance() {
return new WaterAnalysisFragment();
}
@Override
protected void initEventAndData() {
webView = WebViewTool.getInstance().getWebView(url);
if (webView != null) {
int childCount = ll.getChildCount();
if (childCount > 0) {
} else {
ll.addView(webView);
}
} else {
webView = new MyWebView(mContext, url);
webView.loadWebUrl(url);
ll.addView(webView);
}
}
/**
* 如果放在 onDestroyView中销毁容易报错：Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
* 快速返回activity在快速重复进入就会报错，因为onDestroyView 有一定延迟；=按返回家不一定销毁
*/
@Override
public void onPause() {
if (webView != null) {
WebViewTool.getInstance().removeWebView(webView);
}
super.onPause();
}
}
---------------------ok，这样就实现了加载webview秒开的效果-------------------------------------------------
补充预加载相关类：
1：需要预加载的url地址
public class Urls {
private static List<String> urls; // 需要预加载的url集合
static {
urls = new ArrayList<>();
urls.add("https://www.baidu.com/");
urls.add("http://192.168.0.96:8888/onlinemonitoring");
urls.add("http://192.168.0.96:8888/wateranalysis");
}
public static List<String> getUrls() {
return urls;
}
}
2：给webview加个进度条；
public class MyWebView extends WebView {
private Context mContext;
private ProgressBar progressbar; //顶部进度条
private int progressHeight = 8; //进度条的高度，默认8px
MyWebChromeClient WebChromeClient;
public MyWebView(Context context, String url) {
super(context);
mContext = context;
if (url!=null){
loadWebUrl(url);
}
setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT));
initWebViewSettings();
}
/**在xml布局文件中定义的时候调用*/
public MyWebView(Context context, AttributeSet attrs, String url) {
super(context, attrs);
mContext = context;
if (url!=null){
loadWebUrl(url);
}
initWebViewSettings();
setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT));
}
private void initWebViewSettings(){
WebSettings settings = getSettings();
settings.setJavaScriptEnabled(true);//设置WebView是否允许执行JavaScript脚本，默认false，不允许。
settings.setJavaScriptCanOpenWindowsAutomatically(true);
settings.setBuiltInZoomControls(false);
settings.setDomStorageEnabled(true);
settings.setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);
settings.setDatabaseEnabled(true);
settings.setAppCacheEnabled(true);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
settings.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
}
//创建进度条
progressbar = new ProgressBar(mContext, null, android.R.attr.progressBarStyleHorizontal);
// proDialog=new ProgressBar(mContext, null, android.R.attr.progressBarStyleLarge);
//设置加载进度条的高度
progressbar.setLayoutParams(new LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT, progressHeight, 0, 0));
Drawable drawable = mContext.getResources().getDrawable(R.drawable.progress_bar_states);
progressbar.setProgressDrawable(drawable);
// 将proDialog设置到容器的中央位置
//添加进度到WebView
addView(progressbar);
WebChromeClient= new MyWebChromeClient(getContext(),progressbar);
setWebChromeClient(WebChromeClient);
}
/**加载远程网页
* @param webUrl - 远程网页链接地址：比如http://m.baidu.com/*/
public void loadWebUrl(String webUrl){
this.loadUrl(webUrl);
}
/**加载本地assets目录下的网页
* @param localUrl - assets目录下的路径：比如www/login.html*/
public void loadLocalUrl(final String localUrl){
this.loadUrl("file:///android_asset/"+localUrl);
}
...
}
3：管理类：
public class WebViewTool {
private Map<String, MyWebView> webViews = new HashMap<>();
private static class LazyHolder {
private static final WebViewTool INSTANCE = new WebViewTool();
}
private WebViewTool() {
}
public static final WebViewTool getInstance() {
return LazyHolder.INSTANCE;
}
public Map<String, MyWebView> getWebViews() {
return webViews;
}
public void putWebView(String url, MyWebView webView) {
webViews.put(url, webView);
}
public MyWebView getWebView(String url){
MyWebView webView=webViews.get(url);
if (webView!=null){
return webView;
}
return null;
}
public void destoryAll(){
for(Map.Entry<String, MyWebView> entry: webViews.entrySet())
{
String key=entry.getKey();
MyWebView webView= entry.getValue();
webView.stopLoading();
webViews.remove(key);
}
}
public void removeWebView(MyWebView webView) {
// webView.loadDataWithBaseURL(null, "", "text/html", "utf-8", null);
//webView.clearHistory();
if (webView!=null){
((ViewGroup) webView.getParent()).removeView(webView);
}
}
}
4：其他优化，慢慢做去，时间太忙，刚刚实现的顺带做了个笔记；
