使用Application子类空指针错误

Question

你有实现这个方法吗？
getPlayModeSingle提示null指针一般是运行时的， 编译时提示？ 一般不大可能

Answer 1

运行时提示 ，就是run的时候中断了，log里提示空指针，
在CommonApplication中，实现了getPlayModeSingle方法。

Answer 2

可能用的还是系统的APP吧ActivityThread中 attach Application的代码在： try {
            Application app = r.packageInfo.makeApplication(false);
            
            if (localLOGV) Log.v(TAG, "Performing launch of " + r);
            if (localLOGV) Log.v(
                    TAG, r + ": app=" + app
                    + ", appName=" + app.getPackageName()
                    + ", pkg=" + r.packageInfo.getPackageName()
                    + ", comp=" + r.intent.getComponent().toShortString()
                    + ", dir=" + r.packageInfo.getAppDir());            if (activity != null) {
                ApplicationContext appContext = new ApplicationContext();
                appContext.init(r.packageInfo, r.token, this);
                appContext.setOuterContext(activity);
                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
                Configuration config = new Configuration(mConfiguration);
                activity.attach(appContext, this, getInstrumentation(), r.token,
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstance,
                        r.lastNonConfigurationChildInstances, config);
                
                if (customIntent != null) {
                    activity.mIntent = customIntent;
                }
                r.lastNonConfigurationInstance = null;
                r.lastNonConfigurationChildInstances = null;
                activity.mStartedActivity = false;
                int theme = r.activityInfo.getThemeResource();
                if (theme != 0) {
                    activity.setTheme(theme);
                }                activity.mCalled = false;
                mInstrumentation.callActivityOnCreate(activity, r.state);
                if (!activity.mCalled) {
                    throw new SuperNotCalledException(
                        "Activity " + r.intent.getComponent().toShortString() +
                        " did not call through to super.onCreate()");
                }
                r.activity = activity;
                r.stopped = true;
                if (!r.activity.mFinished) {
                    activity.performStart();
                    r.stopped = false;
                }
                if (!r.activity.mFinished) {
                    if (r.state != null) {
                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
                    }
                }
                if (!r.activity.mFinished) {
                    activity.mCalled = false;
                    mInstrumentation.callActivityOnPostCreate(activity, r.state);
                    if (!activity.mCalled) {
                        throw new SuperNotCalledException(
                            "Activity " + r.intent.getComponent().toShortString() +
                            " did not call through to super.onPostCreate()");
                    }
                }
                r.state = null;
            }
            r.paused = true;            mActivities.put(r.token, r);        } catch (SuperNotCalledException e) {
            throw e;        } catch (Exception e) {
            if (!mInstrumentation.onException(activity, e)) {
                throw new RuntimeException(
                    "Unable to start activity " + component
                    + ": " + e.toString(), e);
            }
        }
其中makeApplication的代码，可能要调一下：
public Application makeApplication(boolean forceDefaultAppClass) {
            if (mApplication != null) {
                return mApplication;
            }
            
            Application app = null;
            
            String appClass = mApplicationInfo.className;
            if (forceDefaultAppClass || (appClass == null)) {
                appClass = "android.app.Application";
            }            try {
                java.lang.ClassLoader cl = getClassLoader();
                ApplicationContext appContext = new ApplicationContext();
                appContext.init(this, null, mActivityThread);
                app = mActivityThread.mInstrumentation.newApplication(
                        cl, appClass, appContext);
                appContext.setOuterContext(app);
            } catch (Exception e) {
                if (!mActivityThread.mInstrumentation.onException(app, e)) {
                    throw new RuntimeException(
                        "Unable to instantiate application " + appClass
                        + ": " + e.toString(), e);
                }
            }
            mActivityThread.mAllApplications.add(app);
            return mApplication = app;
        }

Answer 3

android:name=".CommonApplication"改成完整的名字试试？android:name="com.xxx.xxx.CommonApplication"从源代码看，估计这个name直接赋值给mApplicationInfo.className的