Android第九讲——网络（一）

网络连接：
Java中URLConnection HttpClient
Android中也支持
6.0中不太支持
查看手机的网络状态 ， 先创建网络连接管理器 需要加权限

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>    <uses-permission android:name="android.permission.INTERNET"/>

ConnectivityManager getSystemService
访问网络时，可以用WebView来返回网页，但是用时注意
mWebView.getSettings().setJavaScriptEnabled(true);用来加载网页中的jsp的
setWebChromeClient//一般来说用来动态显示progressBar
setWebViewClient//onPageStarted开始加载时；onPageFinished加载完成时；onReceivedError//加载失败时

public class MainActivity extends Activity implements View.OnClickListener{    private TextView mTextViewDetail;    private Button mBtnNetDetail;    private ConnectivityManager manager;    private WebView mWebView;    private Button mBtnAddWeb;    private ProgressBar mProgressBar;    private TextView mTextViewError;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mTextViewDetail = (TextView) findViewById(R.id.textview_net_detail);        mWebView = (WebView) findViewById(R.id.webview);        mBtnNetDetail = (Button) findViewById(R.id.button_get_net_detail);        mBtnAddWeb = (Button) findViewById(R.id.button_webview_add);        mProgressBar = (ProgressBar) findViewById(R.id.progressbar);        mTextViewError = (TextView) findViewById(R.id.textview_net_error);        mBtnNetDetail.setOnClickListener(this);        mBtnAddWeb.setOnClickListener(this);        manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);//初始化manager        mWebView.getSettings().setJavaScriptEnabled(true);        mWebView.setWebChromeClient(new WebChromeClient(){            //进度条改变            @Override            public void onProgressChanged(WebView view, int newProgress) {                super.onProgressChanged(view, newProgress);                mProgressBar.setProgress(newProgress);            }        });        mWebView.setWebViewClient(new WebViewClient(){            @Override            public void onPageStarted(WebView view, String url, Bitmap favicon) {                super.onPageStarted(view, url, favicon);                mProgressBar.setVisibility(View.VISIBLE);            }            @Override            public void onPageFinished(WebView view, String url) {                super.onPageFinished(view, url);                mProgressBar.setVisibility(View.INVISIBLE);            }            @Override            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {                super.onReceivedError(view, errorCode, description, failingUrl);                mWebView.setVisibility(View.GONE);                mTextViewError.setText("对不起，加载失败");                mTextViewError.setVisibility(View.VISIBLE);            }        });//加上        mWebView.getSettings().setBuiltInZoomControls(true);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button_get_net_detail:                NetworkInfo info = manager.getActiveNetworkInfo();//获取网络连接信息                if (info!=null&&info.isConnected()) {                    Toast.makeText(MainActivity.this, "有网络连接", Toast.LENGTH_SHORT).show();                    String type = info.getTypeName();//获取连接状态名                    mTextViewDetail.setText(type);                }else {                    Toast.makeText(MainActivity.this, "无网络连接", Toast.LENGTH_SHORT).show();                    mTextViewDetail.setText("无网络连接");                }                break;            case R.id.button_webview_add:                mWebView.loadUrl("http://www.baidu.com");                break;        }    }}

一般来说按返回键会直接销毁掉Activity，为了按返回键返回到上一个页面，加入下边代码

   @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK){            if (mWebView.canGoBack()){                mWebView.goBack();                return true;//一定要返回            }else {//如果没有WebView能够返回，那么销毁Activity                finish();                return true;            }        }        return super.onKeyDown(keyCode, event);    }

运行结果如图：