1.加载H5提示ERR_CLEARTEXT_NOT_PERMITTED

解决方案：在manifest的application中添加android:usesCleartextTraffic="true"

<?xml version="1.0" encoding="utf-8"?>
<manifest ...>
    <uses-permission android:name="android.permission.INTERNET" />
    <application
        ...
        android:usesCleartextTraffic="true"
        ...>
        ...
    </application>
</manifest>

2.内容宽度获取适配

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.webkit.JavascriptInterface;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class Main extends AppCompatActivity {
    private final Activity activity = this;
    private WebView webView;
    private int contentWidth = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webView = (WebView) findViewById(R.id.webview);
        WebSettings ws = webView.getSettings();
        // 网页内容的宽度是否可大于WebView控件的宽度
        ws.setLoadWithOverviewMode(false);
        // 设置此属性，可任意比例缩放。
        ws.setUseWideViewPort(true);
        // 不缩放
        // webView.setInitialScale(100);
        // 告诉WebView启用JavaScript执行。默认的是false。
        ws.setJavaScriptEnabled(true);
        webView.addJavascriptInterface(new JavaScriptInterface(), "HTMLOUT");
        webView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(WebView view, String url) {
                if (contentWidth == 0) {
                  webView.loadUrl("javascript:window.HTMLOUT.getContentWidth(document.getElementsByTagName('html')[0].scrollWidth);");
                }
            }
        });
        webView.loadUrl("http://file.aimymusic.com/privacyClause.html");
    }

    class JavaScriptInterface {
        @JavascriptInterface
        public void getContentWidth(String value) {
            if (value != null) {
                contentWidth = Integer.parseInt(value);
                final float size = activity.getResources().getDisplayMetrics().widthPixels * 100f / contentWidth;
                Log.e("CASE", "size=" + size);
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        webView.setInitialScale((int) size);//可能会出现从大字体变为小字体的闪一下效果，可以重新调用初始化，设置setInitialScale后重新加载
                    }
                });
            }
        }
    }
}