از کار افتادن دکمه ها در webViewبعد از رفت و برگشت

ublic void onCr

 ublic void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tv);
        SharedPreferences shp = getSharedPreferences("sett", MODE_PRIVATE);
        SharedPreferences shp2 = getSharedPreferences("sett", MODE_PRIVATE);
        WebView webView = (WebView) findViewById(R.id.webView);
        Button btnback = (Button) findViewById(R.id.btnback);

        webView.loadUrl("file:///android_asset/tv.html");
        webView.getSettings().setBuiltInZoomControls(true);
        webView.getSettings().setJavaScriptEnabled(true);

        webView.addJavascriptInterface(new java1(), "asal");
        webView.addJavascriptInterface(new java2(), "opera");
        webView.addJavascriptInterface(new java3(), "pejman");
        webView.addJavascriptInterface(new java4(), "benyamin");
        boolean chbt = shp.getBoolean("chk", false);
        boolean chbt2 = shp2.getBoolean("chk", false);
        if (chbt2) {
            webView.setBackgroundColor(Color.parseColor("#aaaaaa"));
        }

        if (chbt)
            getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        btnback.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {

            }
        });
    }


    public class java1 {

        public void asal() {
            Intent intent = new Intent(tv_Activity.this, asal_Activity.class);
            tv_Activity.this.startActivity(intent);

        }

    }


    public class java2 {

        public void opera() {
            Intent intent = new Intent(tv_Activity.this, opera_Activity.class);
            tv_Activity.this.startActivity(intent);

        }
    }


    public class java3 {

        public void pejman() {
            Intent intent = new Intent(tv_Activity.this, pejman_Activity.class);
            tv_Activity.this.startActivity(intent);

        }
    }


    public class java4 {

        public void benyamin() {
            Intent intent = new Intent(tv_Activity.this, benyamin_Activity.class);
            tv_Activity.this.startActivity(intent);

        }

    }

}

بعد از ساعت ها تلاش بلاخره درستش کردم این خط  رو جابجا کردم بردم اخر  (به هر حال بی تجربگی دیگه )

webView.loadUrl("file:///android_asset/tv.html");