我创建了一个包含webview的应用程序，可在需要时切换缓存模式。从加载默认到加载缓存其他网络。我遇到的第一个问题是在警报对话框处于活动状态时更改方向时应用程序崩溃。我做的是当我放置时控制方向改变：
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
关于构建webview的方法，我把：
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);
调用警告对话框的方法。但现在，问题是当缓存模式设置为加载缓存其他网络，正在加载缓存以及方向已更改时，应用程序崩溃。我确信只有在加载缓存时才会出现此错误，因为根据我的测试，再次建立连接时它会再次正常工作。
以下是我的主要活动的完整代码，没有导入课程：
public class MainActivity extends Activity
{
private WebView wv;
private ProgressBar progress;
private static String mycaturl="www.sampleurl1.com";
private static String errurl="www.sampleurl2.com";
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitNetwork().build();
StrictMode.setThreadPolicy(policy);
if (reachable(this))
{
Toast.makeText(this, "Reachable", Toast.LENGTH_SHORT).show();
buildwv( savedInstanceState, WebSettings.LOAD_DEFAULT, mycaturl );
}
else
{
Toast.makeText(this, "Unreachable", Toast.LENGTH_SHORT).show();
eolc( savedInstanceState );
}
}
@SuppressLint({ "SetJavaScriptEnabled" })
public void buildwv(Bundle sis, int load, String url)
{
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
setContentView(R.layout.activity_main);
//assigning objects to variables
wv=(WebView) findViewById(R.id.wv);
wv.setWebViewClient( new wvc() );
progress=(ProgressBar) findViewById(R.id.progress);
//websettings
WebSettings ws = wv.getSettings();
ws.setAppCacheMaxSize( 100 * 1024 * 1024 ); // 100MB
ws.setAppCachePath( this.getCacheDir().getAbsolutePath() );
ws.setAllowFileAccess( true );
ws.setAppCacheEnabled( true );
ws.setJavaScriptEnabled( true );
ws.setCacheMode(load);
//if instance is saved, to catch orientation change
if(sis==null)
{ wv.loadUrl(url); }
}
public void eolc(final Bundle sis)
{
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);
AlertDialog.Builder alertDialog = new AlertDialog.Builder( MainActivity.this );
alertDialog.setTitle("PATAY ANG WA-LA!!");
alertDialog.setMessage("Host is unreachable. Load from cache or exit.");
alertDialog.setIcon(R.drawable.tick);
//alertDialog.setCanceledOnTouchOutside(false);
alertDialog.setCancelable(false);
alertDialog.setPositiveButton( "Load from Cache", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog,int which)
{
// Write your code here to execute after dialog
Toast.makeText(getApplicationContext(), "You chose to load cache.", Toast.LENGTH_SHORT).show();
buildwv( sis, WebSettings.LOAD_CACHE_ELSE_NETWORK, mycaturl );
}
});
alertDialog.setNeutralButton( "Help", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
Toast.makeText(getApplicationContext(), "You chose Help. EOLC", Toast.LENGTH_SHORT).show();
buildwv( sis, WebSettings.LOAD_CACHE_ELSE_NETWORK, errurl );
}
});
alertDialog.setNegativeButton( "Exit", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
// Write your code here to execute after dialog
Toast.makeText(getApplicationContext(), "You chose to exit.", Toast.LENGTH_SHORT).show();
finish();
}
});
alertDialog.create();
alertDialog.show();
}
public void roe()
{
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);
AlertDialog.Builder alertDialog = new AlertDialog.Builder( MainActivity.this );
alertDialog.setTitle("TANGA ANG WA-LA!!");
alertDialog.setMessage("Host is unreachable. Restart to load cache or exit.");
alertDialog.setIcon(R.drawable.tick);
alertDialog.setCancelable(false);
alertDialog.setPositiveButton( "Restart", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog,int which)
{
Toast.makeText(getApplicationContext(), "You chose to restart and load cache.", Toast.LENGTH_SHORT).show();
Intent i = getBaseContext().getPackageManager()
.getLaunchIntentForPackage( getBaseContext().getPackageName() );
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK );
startActivity(i);
}
});
alertDialog.setNeutralButton( "Help", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
Toast.makeText(getApplicationContext(), "You chose Help. ROE", Toast.LENGTH_SHORT).show();
wv.stopLoading();
wv.loadUrl( errurl );
}
});
alertDialog.setNegativeButton( "Exit", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
Toast.makeText(getApplicationContext(), "You chose to exit.", Toast.LENGTH_SHORT).show();
finish();
}
});
alertDialog.create();
alertDialog.show();
}
private class wvc extends WebViewClient
{
//when page started loading
public void onPageStarted(WebView view, String url, Bitmap favicon)
{
//circular progress bar open
progress.setVisibility(View.VISIBLE);
//if reachable and setting cache on every new page
//setcache(getApplicationContext());
if (url==mycaturl)
{
WebSettings ws = wv.getSettings();
if ( !reachable(getApplicationContext()) )
{
if ( ws.getCacheMode() == WebSettings.LOAD_DEFAULT )
{
roe();
}
else if ( ws.getCacheMode() == WebSettings.LOAD_CACHE_ELSE_NETWORK )
{
Toast.makeText(getApplicationContext(), "loading cache coz not reachable", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(), "websetting out of range", Toast.LENGTH_SHORT).show();
}
}
}
}
//when page finished
@Override
public void onPageFinished(WebView view, String url)
{
super.onPageFinished(view, mycaturl);
Toast.makeText(getApplicationContext(), "PAGE DONE LOADING!!", Toast.LENGTH_SHORT).show();
//circular progress bar close
progress.setVisibility(View.GONE);
}
//when received an error
@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl)
{
wv.stopLoading();
//wv.loadUrl("file:///android_asset/otherpages/errorpage.htm");
WebSettings ws = wv.getSettings();
if ( ws.getCacheMode() == WebSettings.LOAD_DEFAULT )
{
Toast.makeText(getApplicationContext(), "Page unavailable", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(), "Page not cached", Toast.LENGTH_SHORT).show();
}
roe();
}
}
//checking connectivity by checking if site is reachable
public static boolean reachable(Context context)
{
final ConnectivityManager connMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
final NetworkInfo netInfo = connMgr.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnected())
{
try
{
URL url = new URL(mycaturl);
HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
urlc.setConnectTimeout(5000); // five seconds timeout in milliseconds
urlc.connect();
if (urlc.getResponseCode() == 200) // good response
{ return true; } else { return false; }
}
catch (IOException e)
{ return false; }
}
else
{ return false; }
}
//options menu inflation
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
// inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
//when back button is pressed
public void onBackPressed ()
{
if (wv.isFocused() && wv.canGoBack())
{ wv.goBack(); } else { finish(); }
}
//when options button is pressed
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case R.id.item1:
wv.loadUrl( errurl );
break;
case R.id.item2:
String currurl=wv.getUrl();
wv.loadUrl(currurl);
break;
case R.id.item3:
Intent i = getBaseContext().getPackageManager()
.getLaunchIntentForPackage( getBaseContext().getPackageName() );
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
break;
case R.id.item4:
finish();
break;
default:
break;
}
return true;
}
//saving instance state
@Override
protected void onSaveInstanceState(Bundle outState )
{
super.onSaveInstanceState(outState);
wv.saveState(outState);
}
//restoring instance state
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState)
{
super.onSaveInstanceState(savedInstanceState);
wv.restoreState(savedInstanceState);
}
}
这是我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.msiecsapps.mycatlog"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.msiecsapps.mycatlog.Splash"
android:label="@string/app_name"
android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.msiecsapps.mycatlog.MainActivity"
android:label="@string/app_name" >
</activity>
</application>
</manifest>
以下是Logcat上显示的一些内容：
08-23 15:23:13.615: V/MediaPlayer(31183): disconnect
08-23 15:23:13.615: V/MediaPlayer(31183): destructor
08-23 15:23:13.615: W/SurfaceView(31183): CHECK surface infomation creating=false formatChanged=false sizeChanged=false visible=false visibleChanged=true surfaceChanged=true realSizeChanged=false redrawNeeded=false left=false top=false
08-23 15:23:13.650: V/MediaPlayer(31183): disconnect
08-23 15:23:47.375: I/webclipboard(31183): clipservice: android.sec.clipboard.ClipboardExManager@41eaae10
08-23 15:23:47.470: V/webkit(31183): BrowserFrame constructor: this=Handler (android.webkit.BrowserFrame) {41eaac20}
08-23 15:23:47.610: E/SpannableStringBuilder(31183): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
08-23 15:23:47.610: E/SpannableStringBuilder(31183): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
08-23 15:23:47.705: I/GATE(31183): <GATE-M>DEV_ACTION_COMPLETED</GATE-M>
08-23 15:23:51.575: D/dalvikvm(31183): GC_CONCURRENT freed 215K, 9% free 13356K/14599K, paused 2ms+3ms, total 29ms
08-23 15:23:51.580: V/MediaPlayer-JNI(31183): native_finalize
08-23 15:23:51.580: V/MediaPlayer-JNI(31183): release
08-23 15:23:51.620: D/AndroidRuntime(31183): Shutting down VM
08-23 15:23:51.620: W/dalvikvm(31183): threadid=1: thread exiting with uncaught exception (group=0x410a82a0)
08-23 15:23:51.630: E/AndroidRuntime(31183): FATAL EXCEPTION: main
08-23 15:23:51.630: E/AndroidRuntime(31183): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.msiecsapps.mycatlog/com.msiecsapps.mycatlog.MainActivity}: java.lang.NullPointerException
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3553)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.access$700(ActivityThread.java:140)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1233)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.os.Handler.dispatchMessage(Handler.java:99)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.os.Looper.loop(Looper.java:137)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.main(ActivityThread.java:4898)
08-23 15:23:51.630: E/AndroidRuntime(31183): at java.lang.reflect.Method.invokeNative(Native Method)
08-23 15:23:51.630: E/AndroidRuntime(31183): at java.lang.reflect.Method.invoke(Method.java:511)
08-23 15:23:51.630: E/AndroidRuntime(31183): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
08-23 15:23:51.630: E/AndroidRuntime(31183): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
08-23 15:23:51.630: E/AndroidRuntime(31183): at dalvik.system.NativeStart.main(Native Method)
08-23 15:23:51.630: E/AndroidRuntime(31183): Caused by: java.lang.NullPointerException
08-23 15:23:51.630: E/AndroidRuntime(31183): at com.msiecsapps.mycatlog.MainActivity.onRestoreInstanceState(MainActivity.java:332)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.Activity.performRestoreInstanceState(Activity.java:944)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1134)
08-23 15:23:51.630: E/AndroidRuntime(31183): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2078)
08-23 15:23:51.630: E/AndroidRuntime(31183): ... 12 more
08-23 15:24:06.700: I/Process(31183): Sending signal. PID: 31183 SIG: 9
08-23 15:24:07.240: D/AndroidRuntime(1122): Shutting down VM
08-23 15:24:07.240: W/dalvikvm(1122): threadid=1: thread exiting with uncaught exception (group=0x410a82a0)
08-23 15:24:07.245: E/AndroidRuntime(1122): FATAL EXCEPTION: main
08-23 15:24:07.245: E/AndroidRuntime(1122): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.msiecsapps.mycatlog/com.msiecsapps.mycatlog.MainActivity}: java.lang.NullPointerException
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread.access$600(ActivityThread.java:140)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.os.Handler.dispatchMessage(Handler.java:99)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.os.Looper.loop(Looper.java:137)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread.main(ActivityThread.java:4898)
08-23 15:24:07.245: E/AndroidRuntime(1122): at java.lang.reflect.Method.invokeNative(Native Method)
08-23 15:24:07.245: E/AndroidRuntime(1122): at java.lang.reflect.Method.invoke(Method.java:511)
08-23 15:24:07.245: E/AndroidRuntime(1122): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
08-23 15:24:07.245: E/AndroidRuntime(1122): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
08-23 15:24:07.245: E/AndroidRuntime(1122): at dalvik.system.NativeStart.main(Native Method)
08-23 15:24:07.245: E/AndroidRuntime(1122): Caused by: java.lang.NullPointerException
08-23 15:24:07.245: E/AndroidRuntime(1122): at com.msiecsapps.mycatlog.MainActivity.onRestoreInstanceState(MainActivity.java:332)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.Activity.performRestoreInstanceState(Activity.java:944)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1134)
08-23 15:24:07.245: E/AndroidRuntime(1122): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2078)
08-23 15:24:07.245: E/AndroidRuntime(1122): ... 11 more
我认为这些日志来自我的启动画面断开连接，检查网站是否可访问，选择从缓存加载（设置缓存模式加载缓存其他网络），以及加载缓存页面时我倾斜了电话来改变方向。在那里，虚拟机被关闭了。
请帮帮我。提前谢谢。
答案 0 :(得分：1)
在你做其他事之前：
为了能够处理android的问题/开发，你需要上面的内容。
之后： “我遇到的第一个问题是，当警报对话框处于活动状态时，方向更改时应用程序崩溃” =＆GT;回去一步，回到这个问题。您应该能够以另一种方式处理此问题，请在此处打印此问题的logcat日志，以便我们为您提供帮助。