public class MainActivity extends AppCompatActivity {
private WebView wv;
    private ProgressDialog pd;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
    }
    private void init() {
        wv=(WebView)findViewById(R.id.webView);
        wv.loadUrl("http://www.bilibili.com");
        //使得网页从WebView中打开，而不是跳转
        wv.setWebViewClient(new WebViewClient(){
            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                view.loadUrl(url);
                return true;

            }
        });
        //判断页面加载过程
        wv.setWebChromeClient(new WebChromeClient(){
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                if(newProgress==100){
                    closeDialog();
                }else {
                    openDialog(newProgress);
                }
            }
            private void openDialog(int newProgress) {
                //如果对话框等于空，也就是没有对话框
                if(pd==null){
                    //设定一个新的对话框
                    pd=new ProgressDialog(MainActivity.this);
                    //设置标题
                    pd.setTitle("加载中。。。");
                    pd.setIcon(R.mipmap.ic_launcher);
                    //设置对话框进度条样式，设置为横向
                    pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
                    //设置进度，随刷新进度改变
                    pd.setProgress(newProgress );
                    pd.show();

                }else{
                    pd.setProgress(newProgress );
                }
            }
            private void closeDialog() {
                if(pd!=null&&pd.isShowing()){
                    pd.dismiss();
                    pd=null;
                }
            }
        });
    }
    //改写前进与后退的逻辑,使得物理返回按钮默认为上一页面
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode==KeyEvent.KEYCODE_BACK){
            if(wv.canGoBack()){
                wv.goBack();
                return true;
            }else {
                System.exit(0);
            }
        }
        return super.onKeyDown(keyCode, event);
    }
}

详细一点你这个,搞不懂啊