通过 webview 调用网页时，onPageFinished() 会抛出空指针异常。该问题仅在 Android 2.3 上仍然存在，在 Android 4.1 上运行良好。这是我的代码：
public class StoreLocatorActivity extends Activity {
// Declare WebView
WebView storeLocator;
final StoreLocatorActivity activity = this;
boolean homeUrl = false;
// Declare MenuItems
MenuItem homeItem;
MenuItem locationsItem;
MenuItem preQualifyItem;
MenuItem productsItem;
MenuItem logOutItem;
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFeatureInt(Window.FEATURE_PROGRESS,
Window.PROGRESS_VISIBILITY_ON);
this.getWindow().requestFeature(Window.FEATURE_PROGRESS);
setContentView(R.layout.activity_store_locator);
setTitle("");
// Changes to ActionBar
/*ActionBar bar = getActionBar();
bar.setBackgroundDrawable(new ColorDrawable(Color.LTGRAY));
bar.setDisplayShowHomeEnabled(false);// This prevent icon from being
// displayed on ActionBar
*/
callHome();
//logOutItem.setVisible(false).setEnabled(false);
}
public void callHome() {
final ProgressDialog progressDialog = new ProgressDialog(this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setCancelable(false);
storeLocator = (WebView) findViewById(R.id.storeLocator);
storeLocator.setWebViewClient(new WebViewClient());
//storeLocator.getSettings().setJavaScriptEnabled(true);
// storeLocator.getSettings().setBuiltInZoomControls(true);
storeLocator.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
progressDialog.show();
progressDialog.setProgress(0);
activity.setProgress(progress * 1000);
progressDialog.incrementProgressBy(progress);
if (progress == 100 && progressDialog.isShowing())
progressDialog.dismiss();
}
});
storeLocator.loadUrl(getResources().getString(R.string.home));
//storeLocator.loadUrl("http://192.168.0.24/EMG/Login.aspx");
storeLocator.setWebViewClient(new WebViewClient() {
@Override
public void onPageFinished(WebView view, String url) {
if (url.equals(getResources().getString(R.string.accounts))||url.equals(getResources().getString(R.string.accountsalt))) {
homeUrl = true;
System.out.println("in here!!!!!!");
logOutItem.setVisible(true).setEnabled(true);
preQualifyItem.setVisible(false).setEnabled(false);
} else
logOutItem.setVisible(false).setEnabled(false);
System.out.println("Changed url is " + url);
super.onPageFinished(view, url);
}
});
}
菜单项实例化：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_store_locator, menu);
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
homeItem = menu.findItem(R.id.home);
locationsItem = menu.findItem(R.id.location);
preQualifyItem = menu.findItem(R.id.preQualify);
productsItem = menu.findItem(R.id.products);
logOutItem = menu.findItem(R.id.logOut);
// logOutItem = menu.findItem(R.id.logOut);
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.home:
locationsItem.setIcon(R.drawable.locations72);
preQualifyItem.setIcon(R.drawable.prequalify72);
productsItem.setIcon(R.drawable.products72);
// logOutItem.setVisible(true);
item.setIcon(R.drawable.homeb);
final ProgressDialog homeDialog = new ProgressDialog(this);
homeDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
homeDialog.setCancelable(false);
storeLocator = (WebView) findViewById(R.id.storeLocator);
storeLocator.setWebViewClient(new WebViewClient());
//storeLocator.getSettings().setJavaScriptEnabled(true);
// storeLocator.getSettings().setBuiltInZoomControls(true);
storeLocator.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
homeDialog.show();
homeDialog.setProgress(0);
activity.setProgress(progress * 1000);
homeDialog.incrementProgressBy(progress);
if (progress == 100 && homeDialog.isShowing())
homeDialog.dismiss();
}
});
...........................................
这是例外：
05-02 14:06:42.632: E/AndroidRuntime(320): Uncaught handler: thread main exiting due to uncaught exception
05-02 14:06:42.672: E/AndroidRuntime(320): java.lang.NullPointerException
05-02 14:06:42.672: E/AndroidRuntime(320): at com.emg.emgstorelocator.StoreLocatorActivity$2.onPageFinished(StoreLocatorActivity.java:117)
05-02 14:06:42.672: E/AndroidRuntime(320): at android.webkit.CallbackProxy.handleMessage(CallbackProxy.java:242)
05-02 14:06:42.672: E/AndroidRuntime(320): at android.os.Handler.dispatchMessage(Handler.java:99)
05-02 14:06:42.672: E/AndroidRuntime(320): at android.os.Looper.loop(Looper.java:123)
05-02 14:06:42.672: E/AndroidRuntime(320): at android.app.ActivityThread.main(ActivityThread.java:4363)
05-02 14:06:42.672: E/AndroidRuntime(320): at java.lang.reflect.Method.invokeNative(Native Method)
05-02 14:06:42.672: E/AndroidRuntime(320): at java.lang.reflect.Method.invoke(Method.java:521)
05-02 14:06:42.672: E/AndroidRuntime(320): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
05-02 14:06:42.672: E/AndroidRuntime(320): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-02 14:06:42.672: E/AndroidRuntime(320): at dalvik.system.NativeStart.main(Native Method)
无法找出异常的原因。