【android进阶】Fragment内放置WebView，监听返回键，并返回之前打开的网页

来源：互联网发布：java stringbuffer类编辑：程序博客网时间：2024/06/16 07:52

参考链接：http://itindex.net/detail/53169-android-%E5%BC%80%E5%8F%91-webview

http://blog.csdn.net/guxiao1201/article/details/40507387

首先创建一个抽象类BackHandledFragment，该类有一个抽象方法onBackPressed()，所有BackHandledFragment的子类在onBackPressed方法中处理各自对Back事件的消费逻辑。onBackPressed返回布尔值，宿主Activity将会根据该方法的返回值判断子Fragment是否有消费Back事件。此外，宿主FragmentActivity还会保持一份当前Fragment的引用，当用户按下Back键时，宿主Activity会判断当前Fragment是否需要消费该事件，如果没有Fragment消费才会自己消费。

public abstract class BackHandledFragment extends Fragment{    protected BackHandledInterface mBackHandledInterface;    /**     * 所有继承BackHandledFragment的子类都将在这个方法中实现物理Back键按下后的逻辑     * FragmentActivity捕捉到物理返回键点击事件后会首先询问Fragment是否消费该事件     * 如果没有Fragment消息时FragmentActivity自己才会消费该事件     */    public abstract boolean onBackPressed();    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if(!(getActivity() instanceof BackHandledInterface)){            throw new ClassCastException("Hosting Activity must implement BackHandledInterface");        }else{            this.mBackHandledInterface = (BackHandledInterface)getActivity();        }    }    @Override    public void onStart() {        super.onStart();        //告诉FragmentActivity，当前Fragment在栈顶        mBackHandledInterface.setSelectedFragment(this);    }}

宿主FragmentActivity需要实现BackHandledIntegerface，子Fragment会通过该接口告诉宿主FragmentActivity自己是当前屏幕可见的Fragment。

public interface BackHandledInterface {    void setSelectedFragment(BackHandledFragment selectedFragment);}

所以在Fragment的onCreate中会判断宿主FragmentActivity是否已继承了该接口。在Fragment的onStart()方法中就会调用该接口告诉宿主FragmentActivity自己是当前屏幕可见的Fragment。
宿主FragmentActivity就可以在onBackPressed()方法中对Back事件进行判断处理了。

public class MainActivity extends FragmentActivity implements BackHandledInterface{private BackHandledFragment mBackHandedFragment;private boolean hadIntercept;@Overridepublic void setSelectedFragment(BackHandledFragment selectedFragment) {this.mBackHandedFragment = selectedFragment;}@Overridepublic void onBackPressed() {if(mBackHandedFragment == null || !mBackHandedFragment.onBackPressed()){if(getSupportFragmentManager().getBackStackEntryCount() == 0){super.onBackPressed(); //退出}else{getSupportFragmentManager().popBackStack(); //fragment 出栈}}}}

Fragment需要继承抽象类BackHandledFragment，并覆写抽象方法onBackPressed()，在抽象方法中判断WebView是否可以返回到之前打开的网页

public class WorkFragment extends BackHandledFragment {    private WebView webView;    private WebSettings webSettings;    private String url = "https://www.baidu.com/";    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.work_fragment,container,false);        webView = (WebView)view.findViewById(R.id.workWebView);        webSettings = webView.getSettings();        webSettings.setJavaScriptEnabled(true);        webSettings.setUseWideViewPort(true);        webSettings.setLoadWithOverviewMode(true);        webView.setWebViewClient(new MyWebViewClient());        webView.loadUrl(url);        return view;    }    private class MyWebViewClient extends WebViewClient {        @Override        public boolean shouldOverrideUrlLoading(WebView view, String url) {            //    return super.shouldOverrideUrlLoading(view, url);            view.loadUrl(url);            return true;        }        @Override        public void onReceivedError(WebView view, int errorCode,                                    String description, String failingUrl) {            //     super.onReceivedError(view, errorCode, description, failingUrl);            //  Toast.makeText(this,"网页加载错误！",0).show();        }    }    @Override    public  boolean onBackPressed(){        if(webView.canGoBack()){            webView.goBack();            Log.v("webView.goBack()", "webView.goBack()");            return true;        }else{            Log.v("Conversatio退出","Conversatio退出");            return false;        }    }}

4 0