这是我的最后一段代码。我想显示用户网络信息。当用户离线时警告用户 我想在线下或在线向用户展示。我用进度条。当我使用此代码时，我的应用程序崩溃并退出我的应用程序。我该怎么办
ConnectivityManager conMgr;
NetworkInfo netInfo;
private WebView webView;
ProgressDialog progressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_activity1);
Toast.makeText(Activity5.this, "welcome",30000).show();
progressDialog = new ProgressDialog(Activity5.this);
Button btn1 = (Button) findViewById(R.id.buttn1);
btn1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
finish();
System.exit(0);
}
});
Button b = (Button) findViewById(R.id.button10);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Activity5.this, Activity2.class));
}
});
String url = "http://student.iaun.ac.ir";
webView = (WebView) findViewById(R.id.webView2);
webView.setWebViewClient(new myWebViewClient());
webView.getSettings().setJavaScriptEnabled(false);
webView.getSettings().setLoadWithOverviewMode(true);
webView.getSettings().setUseWideViewPort(true);
webView.getSettings().setBuiltInZoomControls(true);
webView.loadUrl(url);
webView.getSettings().setSavePassword(false);
Button button = (Button) findViewById(R.id.new_button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(new Intent(Activity5.this, Prefs.class));
}
});
progressDialog.setMessage("please wait web page is loading");
progressDialog.setCancelable(false);
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.show();
new Handler().postDelayed(new Runnable() {
public void run() {
progressDialog.dismiss();
}
}, 25000);
progressDialog = new ProgressDialog(Activity5.this);
if (isOnline()) {
/*Your Code*/
}
else{
try {
AlertDialog alertDialog = new AlertDialog.Builder(
Activity5.this).create();
alertDialog.setTitle("Info");
alertDialog.setMessage("Please check your internet connection");
alertDialog.setButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
finish();
}
});
alertDialog.show();
} catch (Exception e) {
}
}
new Thread(new Runnable() {
@Override
public void run() {
try {
startDelay();
webView.getSettings().setJavaScriptEnabled(true);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
}
void startDelay() throws InterruptedException {
Thread.sleep(15000);
}
private boolean isOnline() {
conMgr = (ConnectivityManager) getApplicationContext()
.getSystemService(Context.CONNECTIVITY_SERVICE);
netInfo = conMgr.getActiveNetworkInfo();
if (netInfo == null || !netInfo.isConnected() || !netInfo.isAvailable()) {
return false;
}
return true;
}
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity1, menu);
return true;
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
// Check if the key event was the Back button and if there's history
if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
webView.goBack();
return true;
}
// If it wasn't the Back key or there's no web page history, bubble up to the default
// system behavior (probably exit the activity)
return super.onKeyDown(keyCode, event);
}
答案 0 :(得分：3)
要点是：
您无法在按钮单击时使用System.exit（0），您可以使用finish（）完成该活动或moveTaskToBack（true）以最小化应用程序。
首先要了解每件事情，然后继续前进，而不仅仅是复制＆amp;粘贴你的代码，理解它背后的概念和逻辑。
如果您需要有关此主题的更多帮助，那么我就在这里，但请花些时间尝试理解逻辑
答案 1 :(得分：1)
我已经更改了代码，现在进度对话框出现了20秒，同时webview也加载了它的内容......
public class Activity1 extends Activity {
private webview webview;
ProgressDialog progressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toast.makeText(getApplicationContext(), "welcome", Toast.LENGTH_LONG)
.show();
progressDialog = new ProgressDialog(Activity1.this);
String url = "http://student.iaun.ac.ir";
webview = (webview) findViewById(R.id.webview);
webview.getSettings().setJavaScriptEnabled(false);
webview.getSettings().setLoadWithOverviewMode(true);
webview.getSettings().setUseWideViewPort(true);
webview.getSettings().setBuiltInZoomControls(true);
webview.loadUrl(url);
progressDialog.setMessage("Loading ...");
progressDialog.setCancelable(false);
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.show();
new Handler().postDelayed(new Runnable() {
public void run() {
progressDialog.dismiss();
}
}, 20000);
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
// Check if the key event was the Back button and if there's history
if ((keyCode == KeyEvent.KEYCODE_BACK) && webview.canGoBack()) {
webview.goBack();
return true;
}
// If it wasn't the Back key or there's no web page history, bubble up
// to the default
// system behavior (probably exit the activity)
return super.onKeyDown(keyCode, event);
}
}
答案 2 :(得分：0)
你必须使用WebViewClient，并覆盖onPageStarted（），onpageFinished（）等方法......
public class WebActivity extends Activity {
private WebView browser;
ProgressDialog progressDialog;
ConnectivityManager conMgr;
NetworkInfo netInfo;
String url;
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web_activity);
browser = (WebView) findViewById(R.id.shop);
progressDialog = new ProgressDialog(WebActivity.this);
if (isOnline()) {
browser.getSettings().setDomStorageEnabled(true);
browser.getSettings().setJavaScriptEnabled(true);
browser.loadUrl(/*Your url paste here*/);
browser.setWebViewClient(new WebViewClient() {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
return false;
}
@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
progressDialog.dismiss();
}
@Override
public void onPageStarted(WebView view, String url,
Bitmap favicon) {
// TODO Auto-generated method stub
super.onPageStarted(view, url, favicon);
progressDialog.setMessage("Loading ...");
progressDialog.setCancelable(false);
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.show();
}
});
} else {
try {
AlertDialog alertDialog = new AlertDialog.Builder(
WebActivity.this).create();
alertDialog.setTitle("Info");
alertDialog.setMessage("Please check your internet connection");
alertDialog.setButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
finish();
}
});
alertDialog.show();
} catch (Exception e) {
}
}
}
private boolean isOnline() {
conMgr = (ConnectivityManager) getApplicationContext()
.getSystemService(Context.CONNECTIVITY_SERVICE);
netInfo = conMgr.getActiveNetworkInfo();
if (netInfo == null || !netInfo.isConnected() || !netInfo.isAvailable()) {
return false;
}
return true;
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && browser.canGoBack()) {
browser.goBack();
return true;
} else {
moveTaskToBack(true);
return super.onKeyDown(keyCode, event);
}
}
}
这是检查用户网络状态的代码......
ConnectivityManager conMgr;
NetworkInfo netInfo;
ProgressDialog progressDialog;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web_activity);
browser = (WebView) findViewById(R.id.shop);
progressDialog = new ProgressDialog(WebActivity.this);
if (isOnline()) {
/*Your Code*/
}
else{
try {
AlertDialog alertDialog = new AlertDialog.Builder(
WebActivity.this).create();
alertDialog.setTitle("Info");
alertDialog.setMessage("Please check your internet connection");
alertDialog.setButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
finish();
}
});
alertDialog.show();
} catch (Exception e) {
}
}
这是检查状态的isOnline（）方法......
private boolean isOnline() {
conMgr = (ConnectivityManager) getApplicationContext()
.getSystemService(Context.CONNECTIVITY_SERVICE);
netInfo = conMgr.getActiveNetworkInfo();
if (netInfo == null || !netInfo.isConnected() || !netInfo.isAvailable()) {
return false;
}
return true;
}