Android 原因:java.lang.ClassCastException
说明: 当我点击标题栏上的“到”按钮时,我遇到了ClassCast异常。 我的源代码如下: 我的活动代码:Android 原因:java.lang.ClassCastException,android,android-intent,Android,Android Intent,说明: 当我点击标题栏上的“到”按钮时,我遇到了ClassCast异常。 我的源代码如下: 我的活动代码: public void onClick(View v) { if (v.getId() == R.id.about_us) { if (isInternetConnected()) { System.out.println("about us"); startActivity(new Intent(GridDisp
public void onClick(View v) {
if (v.getId() == R.id.about_us) {
if (isInternetConnected()) {
System.out.println("about us");
startActivity(new Intent(GridDisplayActivity.this, AboutUsActivity.class));
} else {
setAlertBox("No Internet Connection");
}
}
if (v.getId() == R.id.hard_copy) {
if (isInternetConnected()) {
System.out.println("hard copy");
startActivity(new Intent(GridDisplayActivity.this,HardCopyActivity.class));
} else {
setAlertBox("No Internet Connection");
}
}
}
自定义应用程序代码:
public class CustomApplication extends Application {
private Map<String, List<CustomAsyncTask<?,?,?>>> mActivityTaskMap;
public CustomApplication() {
mActivityTaskMap = new HashMap<String, List<CustomAsyncTask<?,?,?>>>();
}
public void removeTask(CustomAsyncTask<?,?,?> task) {
for (Entry<String, List<CustomAsyncTask<?,?,?>>> entry : mActivityTaskMap.entrySet()) {
List<CustomAsyncTask<?,?,?>> tasks = entry.getValue();
for (int i = 0; i < tasks.size(); i++) {
if (tasks.get(i) == task) {
tasks.remove(i);
break;
}
}
if (tasks.size() == 0) {
mActivityTaskMap.remove(entry.getKey());
return;
}
}
}
public void addTask(Activity activity, CustomAsyncTask<?,?,?> task) {
String key = activity.getClass().getCanonicalName();
List<CustomAsyncTask<?,?,?>> tasks = mActivityTaskMap.get(key);
if (tasks == null) {
tasks = new ArrayList<CustomAsyncTask<?,?,?>>();
mActivityTaskMap.put(key, tasks);
}
tasks.add(task);
}
public void detach(Activity activity) {
List<CustomAsyncTask<?,?,?>> tasks = mActivityTaskMap.get(activity.getClass().getCanonicalName());
if (tasks != null) {
for (CustomAsyncTask<?,?,?> task : tasks) {
task.setActivity(null);
}
}
}
public void attach(Activity activity) {
List<CustomAsyncTask<?,?,?>> tasks = mActivityTaskMap.get(activity.getClass().getCanonicalName());
if (tasks != null) {
for (CustomAsyncTask<?,?,?> task : tasks) {
task.setActivity(activity);
}
}
}
07-26 11:06:10.567: E/AndroidRuntime(381): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
07-26 11:06:10.567: E/AndroidRuntime(381): at dalvik.system.NativeStart.main(Native Method)
07-26 11:06:10.567: E/AndroidRuntime(381): Caused by: java.lang.ClassCastException: android.app.Application cannot be cast to com.bespoken.android.provider.CustomApplication
07-26 11:06:10.567: E/AndroidRuntime(381): at com.bespoken.android.GridDisplayActivity.onSaveInstanceState(GridDisplayActivity.java:567)
07-26 11:06:10.567: E/AndroidRuntime(381): at android.app.Activity.performSaveInstanceState(Activity.java:1114)
07-26 11:06:10.567: E/AndroidRuntime(381): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1184)
07-26 11:06:10.567: E/AndroidRuntime(381): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2469)
07-26 11:06:10.567: E/AndroidRuntime(381): ... 12 more
请引导我。
提前感谢。不要执行(CustomApplication)getApplication()
,而是在CustomApplication
类中有一个静态CustomApplication
字段,比如分钟
,在CustomApplication中设置它。一旦创建到this
并在您想要访问CustomApplication'
s方法的任何地方使用它
class CustomApplication extends Application
{
private static CustomApplication mInstance;
@Override
void onCreate() {
super.onCreate();
mInstance = this;
}
public static CustomApplication getInstance() { return mInstance; }
public void mySpecificMethod() { .... }
}
然后从需要的地方打电话:
CustomApplication.getInstance()->mySpecificMethod()
这里的CustomApplication是什么,您正在xml文件GridDisplayActivity中声明它。java:567这一行是罪魁祸首。GridDisplayActivity的第567行上有什么内容与旋转处理一起有一个asynTask,因此第567行上的“((CustomApplication)getApplication())。detach(this);”在public void onSaveInstanceState(Bundle outState){super.onSaveInstanceState(outState);@Richa Laad我编辑了答案,建议在使用(CustomApplication.getInstance())时使用一段代码。在活动的onSaveInstanceState(Bundle outState)上分离(this),我得到了java.lang。NullPointerException@RichaLaad您的manifest.xml中是否有自定义应用程序Ohh..我第一次没有指定as处理自定义应用程序,谢谢alex的帮助。我已在manifest.xml文件中添加了自定义应用程序,它对我有效。