java.lang.NullPointerException：预期类型为android.app.ActionBar的接收器，但获取了null

Question

我有一个使用导航抽屉的应用程序，该应用程序在手机上运行良好。 但这在仿真器上不起作用。 如果我单击导航抽屉上的任何项目。 仿真器只是挂起。

这是我在Logcat中得到的：

08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745): Couldn't set home-as-up indicator via JB-MR2 API
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745): java.lang.NullPointerException: expected receiver of type android.app.ActionBar, but got null
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at java.lang.reflect.Method.invokeNative(Native Method)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at java.lang.reflect.Method.invoke(Method.java:515)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at android.support.v4.app.ActionBarDrawerToggleHoneycomb.setActionBarUpIndicator(ActionBarDrawerToggleHoneycomb.java:55)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at android.support.v4.app.ActionBarDrawerToggle$ActionBarDrawerToggleImplHC.setActionBarUpIndicator(ActionBarDrawerToggle.java:130)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at android.support.v4.app.ActionBarDrawerToggle.setActionBarUpIndicator(ActionBarDrawerToggle.java:372)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at android.support.v4.app.ActionBarDrawerToggle.syncState(ActionBarDrawerToggle.java:230)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at com.places.logic.NavDrawerActivity.onPostCreate(NavDrawerActivity.java:199)
08-01 00:11:08.342: W/ActionBarDrawerToggleHoneycomb(2745):     at android.app.Instrumentation.callActivityOnPostCreate(Instrumentation.java:1150)

显示NullPointerException的行是

 @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

我的mDrawwerToggle初始化代码：

mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
                ) {
            public void onDrawerClosed(View view) {
           //     getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
            //    getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

Answer 1

删除您的onPostCreateMethod()然后试试看

mDrawerLayout.post(new Runnable() {

        @Override
        public void run() {
            mDrawerToggle.syncState();
        }
});